1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.widget;
18
19import android.annotation.IntDef;
20import android.annotation.NonNull;
21import android.content.Context;
22import android.content.Intent;
23import android.content.res.TypedArray;
24import android.graphics.Rect;
25import android.os.Bundle;
26import android.os.Trace;
27import android.util.AttributeSet;
28import android.util.MathUtils;
29import android.view.Gravity;
30import android.view.KeyEvent;
31import android.view.SoundEffectConstants;
32import android.view.View;
33import android.view.ViewDebug;
34import android.view.ViewGroup;
35import android.view.ViewHierarchyEncoder;
36import android.view.ViewRootImpl;
37import android.view.accessibility.AccessibilityNodeInfo;
38import android.view.accessibility.AccessibilityNodeInfo.AccessibilityAction;
39import android.view.accessibility.AccessibilityNodeProvider;
40import android.view.accessibility.AccessibilityNodeInfo.CollectionInfo;
41import android.view.accessibility.AccessibilityNodeInfo.CollectionItemInfo;
42import android.view.animation.GridLayoutAnimationController;
43import android.widget.RemoteViews.RemoteView;
44
45import com.android.internal.R;
46
47import java.lang.annotation.Retention;
48import java.lang.annotation.RetentionPolicy;
49
50
51/**
52 * A view that shows items in two-dimensional scrolling grid. The items in the
53 * grid come from the {@link ListAdapter} associated with this view.
54 *
55 * <p>See the <a href="{@docRoot}guide/topics/ui/layout/gridview.html">Grid
56 * View</a> guide.</p>
57 *
58 * @attr ref android.R.styleable#GridView_horizontalSpacing
59 * @attr ref android.R.styleable#GridView_verticalSpacing
60 * @attr ref android.R.styleable#GridView_stretchMode
61 * @attr ref android.R.styleable#GridView_columnWidth
62 * @attr ref android.R.styleable#GridView_numColumns
63 * @attr ref android.R.styleable#GridView_gravity
64 */
65@RemoteView
66public class GridView extends AbsListView {
67    /** @hide */
68    @IntDef({NO_STRETCH, STRETCH_SPACING, STRETCH_COLUMN_WIDTH, STRETCH_SPACING_UNIFORM})
69    @Retention(RetentionPolicy.SOURCE)
70    public @interface StretchMode {}
71
72    /**
73     * Disables stretching.
74     *
75     * @see #setStretchMode(int)
76     */
77    public static final int NO_STRETCH = 0;
78    /**
79     * Stretches the spacing between columns.
80     *
81     * @see #setStretchMode(int)
82     */
83    public static final int STRETCH_SPACING = 1;
84    /**
85     * Stretches columns.
86     *
87     * @see #setStretchMode(int)
88     */
89    public static final int STRETCH_COLUMN_WIDTH = 2;
90    /**
91     * Stretches the spacing between columns. The spacing is uniform.
92     *
93     * @see #setStretchMode(int)
94     */
95    public static final int STRETCH_SPACING_UNIFORM = 3;
96
97    /**
98     * Creates as many columns as can fit on screen.
99     *
100     * @see #setNumColumns(int)
101     */
102    public static final int AUTO_FIT = -1;
103
104    private int mNumColumns = AUTO_FIT;
105
106    private int mHorizontalSpacing = 0;
107    private int mRequestedHorizontalSpacing;
108    private int mVerticalSpacing = 0;
109    private int mStretchMode = STRETCH_COLUMN_WIDTH;
110    private int mColumnWidth;
111    private int mRequestedColumnWidth;
112    private int mRequestedNumColumns;
113
114    private View mReferenceView = null;
115    private View mReferenceViewInSelectedRow = null;
116
117    private int mGravity = Gravity.START;
118
119    private final Rect mTempRect = new Rect();
120
121    public GridView(Context context) {
122        this(context, null);
123    }
124
125    public GridView(Context context, AttributeSet attrs) {
126        this(context, attrs, R.attr.gridViewStyle);
127    }
128
129    public GridView(Context context, AttributeSet attrs, int defStyleAttr) {
130        this(context, attrs, defStyleAttr, 0);
131    }
132
133    public GridView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
134        super(context, attrs, defStyleAttr, defStyleRes);
135
136        final TypedArray a = context.obtainStyledAttributes(
137                attrs, R.styleable.GridView, defStyleAttr, defStyleRes);
138
139        int hSpacing = a.getDimensionPixelOffset(
140                R.styleable.GridView_horizontalSpacing, 0);
141        setHorizontalSpacing(hSpacing);
142
143        int vSpacing = a.getDimensionPixelOffset(
144                R.styleable.GridView_verticalSpacing, 0);
145        setVerticalSpacing(vSpacing);
146
147        int index = a.getInt(R.styleable.GridView_stretchMode, STRETCH_COLUMN_WIDTH);
148        if (index >= 0) {
149            setStretchMode(index);
150        }
151
152        int columnWidth = a.getDimensionPixelOffset(R.styleable.GridView_columnWidth, -1);
153        if (columnWidth > 0) {
154            setColumnWidth(columnWidth);
155        }
156
157        int numColumns = a.getInt(R.styleable.GridView_numColumns, 1);
158        setNumColumns(numColumns);
159
160        index = a.getInt(R.styleable.GridView_gravity, -1);
161        if (index >= 0) {
162            setGravity(index);
163        }
164
165        a.recycle();
166    }
167
168    @Override
169    public ListAdapter getAdapter() {
170        return mAdapter;
171    }
172
173    /**
174     * Sets up this AbsListView to use a remote views adapter which connects to a RemoteViewsService
175     * through the specified intent.
176     * @param intent the intent used to identify the RemoteViewsService for the adapter to connect to.
177     */
178    @android.view.RemotableViewMethod
179    public void setRemoteViewsAdapter(Intent intent) {
180        super.setRemoteViewsAdapter(intent);
181    }
182
183    /**
184     * Sets the data behind this GridView.
185     *
186     * @param adapter the adapter providing the grid's data
187     */
188    @Override
189    public void setAdapter(ListAdapter adapter) {
190        if (mAdapter != null && mDataSetObserver != null) {
191            mAdapter.unregisterDataSetObserver(mDataSetObserver);
192        }
193
194        resetList();
195        mRecycler.clear();
196        mAdapter = adapter;
197
198        mOldSelectedPosition = INVALID_POSITION;
199        mOldSelectedRowId = INVALID_ROW_ID;
200
201        // AbsListView#setAdapter will update choice mode states.
202        super.setAdapter(adapter);
203
204        if (mAdapter != null) {
205            mOldItemCount = mItemCount;
206            mItemCount = mAdapter.getCount();
207            mDataChanged = true;
208            checkFocus();
209
210            mDataSetObserver = new AdapterDataSetObserver();
211            mAdapter.registerDataSetObserver(mDataSetObserver);
212
213            mRecycler.setViewTypeCount(mAdapter.getViewTypeCount());
214
215            int position;
216            if (mStackFromBottom) {
217                position = lookForSelectablePosition(mItemCount - 1, false);
218            } else {
219                position = lookForSelectablePosition(0, true);
220            }
221            setSelectedPositionInt(position);
222            setNextSelectedPositionInt(position);
223            checkSelectionChanged();
224        } else {
225            checkFocus();
226            // Nothing selected
227            checkSelectionChanged();
228        }
229
230        requestLayout();
231    }
232
233    @Override
234    int lookForSelectablePosition(int position, boolean lookDown) {
235        final ListAdapter adapter = mAdapter;
236        if (adapter == null || isInTouchMode()) {
237            return INVALID_POSITION;
238        }
239
240        if (position < 0 || position >= mItemCount) {
241            return INVALID_POSITION;
242        }
243        return position;
244    }
245
246    /**
247     * {@inheritDoc}
248     */
249    @Override
250    void fillGap(boolean down) {
251        final int numColumns = mNumColumns;
252        final int verticalSpacing = mVerticalSpacing;
253
254        final int count = getChildCount();
255
256        if (down) {
257            int paddingTop = 0;
258            if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
259                paddingTop = getListPaddingTop();
260            }
261            final int startOffset = count > 0 ?
262                    getChildAt(count - 1).getBottom() + verticalSpacing : paddingTop;
263            int position = mFirstPosition + count;
264            if (mStackFromBottom) {
265                position += numColumns - 1;
266            }
267            fillDown(position, startOffset);
268            correctTooHigh(numColumns, verticalSpacing, getChildCount());
269        } else {
270            int paddingBottom = 0;
271            if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
272                paddingBottom = getListPaddingBottom();
273            }
274            final int startOffset = count > 0 ?
275                    getChildAt(0).getTop() - verticalSpacing : getHeight() - paddingBottom;
276            int position = mFirstPosition;
277            if (!mStackFromBottom) {
278                position -= numColumns;
279            } else {
280                position--;
281            }
282            fillUp(position, startOffset);
283            correctTooLow(numColumns, verticalSpacing, getChildCount());
284        }
285    }
286
287    /**
288     * Fills the list from pos down to the end of the list view.
289     *
290     * @param pos The first position to put in the list
291     *
292     * @param nextTop The location where the top of the item associated with pos
293     *        should be drawn
294     *
295     * @return The view that is currently selected, if it happens to be in the
296     *         range that we draw.
297     */
298    private View fillDown(int pos, int nextTop) {
299        View selectedView = null;
300
301        int end = (mBottom - mTop);
302        if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
303            end -= mListPadding.bottom;
304        }
305
306        while (nextTop < end && pos < mItemCount) {
307            View temp = makeRow(pos, nextTop, true);
308            if (temp != null) {
309                selectedView = temp;
310            }
311
312            // mReferenceView will change with each call to makeRow()
313            // do not cache in a local variable outside of this loop
314            nextTop = mReferenceView.getBottom() + mVerticalSpacing;
315
316            pos += mNumColumns;
317        }
318
319        setVisibleRangeHint(mFirstPosition, mFirstPosition + getChildCount() - 1);
320        return selectedView;
321    }
322
323    private View makeRow(int startPos, int y, boolean flow) {
324        final int columnWidth = mColumnWidth;
325        final int horizontalSpacing = mHorizontalSpacing;
326
327        final boolean isLayoutRtl = isLayoutRtl();
328
329        int last;
330        int nextLeft;
331
332        if (isLayoutRtl) {
333            nextLeft = getWidth() - mListPadding.right - columnWidth -
334                    ((mStretchMode == STRETCH_SPACING_UNIFORM) ? horizontalSpacing : 0);
335        } else {
336            nextLeft = mListPadding.left +
337                    ((mStretchMode == STRETCH_SPACING_UNIFORM) ? horizontalSpacing : 0);
338        }
339
340        if (!mStackFromBottom) {
341            last = Math.min(startPos + mNumColumns, mItemCount);
342        } else {
343            last = startPos + 1;
344            startPos = Math.max(0, startPos - mNumColumns + 1);
345
346            if (last - startPos < mNumColumns) {
347                final int deltaLeft = (mNumColumns - (last - startPos)) * (columnWidth + horizontalSpacing);
348                nextLeft += (isLayoutRtl ? -1 : +1) * deltaLeft;
349            }
350        }
351
352        View selectedView = null;
353
354        final boolean hasFocus = shouldShowSelector();
355        final boolean inClick = touchModeDrawsInPressedState();
356        final int selectedPosition = mSelectedPosition;
357
358        View child = null;
359        final int nextChildDir = isLayoutRtl ? -1 : +1;
360        for (int pos = startPos; pos < last; pos++) {
361            // is this the selected item?
362            boolean selected = pos == selectedPosition;
363            // does the list view have focus or contain focus
364
365            final int where = flow ? -1 : pos - startPos;
366            child = makeAndAddView(pos, y, flow, nextLeft, selected, where);
367
368            nextLeft += nextChildDir * columnWidth;
369            if (pos < last - 1) {
370                nextLeft += nextChildDir * horizontalSpacing;
371            }
372
373            if (selected && (hasFocus || inClick)) {
374                selectedView = child;
375            }
376        }
377
378        mReferenceView = child;
379
380        if (selectedView != null) {
381            mReferenceViewInSelectedRow = mReferenceView;
382        }
383
384        return selectedView;
385    }
386
387    /**
388     * Fills the list from pos up to the top of the list view.
389     *
390     * @param pos The first position to put in the list
391     *
392     * @param nextBottom The location where the bottom of the item associated
393     *        with pos should be drawn
394     *
395     * @return The view that is currently selected
396     */
397    private View fillUp(int pos, int nextBottom) {
398        View selectedView = null;
399
400        int end = 0;
401        if ((mGroupFlags & CLIP_TO_PADDING_MASK) == CLIP_TO_PADDING_MASK) {
402            end = mListPadding.top;
403        }
404
405        while (nextBottom > end && pos >= 0) {
406
407            View temp = makeRow(pos, nextBottom, false);
408            if (temp != null) {
409                selectedView = temp;
410            }
411
412            nextBottom = mReferenceView.getTop() - mVerticalSpacing;
413
414            mFirstPosition = pos;
415
416            pos -= mNumColumns;
417        }
418
419        if (mStackFromBottom) {
420            mFirstPosition = Math.max(0, pos + 1);
421        }
422
423        setVisibleRangeHint(mFirstPosition, mFirstPosition + getChildCount() - 1);
424        return selectedView;
425    }
426
427    /**
428     * Fills the list from top to bottom, starting with mFirstPosition
429     *
430     * @param nextTop The location where the top of the first item should be
431     *        drawn
432     *
433     * @return The view that is currently selected
434     */
435    private View fillFromTop(int nextTop) {
436        mFirstPosition = Math.min(mFirstPosition, mSelectedPosition);
437        mFirstPosition = Math.min(mFirstPosition, mItemCount - 1);
438        if (mFirstPosition < 0) {
439            mFirstPosition = 0;
440        }
441        mFirstPosition -= mFirstPosition % mNumColumns;
442        return fillDown(mFirstPosition, nextTop);
443    }
444
445    private View fillFromBottom(int lastPosition, int nextBottom) {
446        lastPosition = Math.max(lastPosition, mSelectedPosition);
447        lastPosition = Math.min(lastPosition, mItemCount - 1);
448
449        final int invertedPosition = mItemCount - 1 - lastPosition;
450        lastPosition = mItemCount - 1 - (invertedPosition - (invertedPosition % mNumColumns));
451
452        return fillUp(lastPosition, nextBottom);
453    }
454
455    private View fillSelection(int childrenTop, int childrenBottom) {
456        final int selectedPosition = reconcileSelectedPosition();
457        final int numColumns = mNumColumns;
458        final int verticalSpacing = mVerticalSpacing;
459
460        int rowStart;
461        int rowEnd = -1;
462
463        if (!mStackFromBottom) {
464            rowStart = selectedPosition - (selectedPosition % numColumns);
465        } else {
466            final int invertedSelection = mItemCount - 1 - selectedPosition;
467
468            rowEnd = mItemCount - 1 - (invertedSelection - (invertedSelection % numColumns));
469            rowStart = Math.max(0, rowEnd - numColumns + 1);
470        }
471
472        final int fadingEdgeLength = getVerticalFadingEdgeLength();
473        final int topSelectionPixel = getTopSelectionPixel(childrenTop, fadingEdgeLength, rowStart);
474
475        final View sel = makeRow(mStackFromBottom ? rowEnd : rowStart, topSelectionPixel, true);
476        mFirstPosition = rowStart;
477
478        final View referenceView = mReferenceView;
479
480        if (!mStackFromBottom) {
481            fillDown(rowStart + numColumns, referenceView.getBottom() + verticalSpacing);
482            pinToBottom(childrenBottom);
483            fillUp(rowStart - numColumns, referenceView.getTop() - verticalSpacing);
484            adjustViewsUpOrDown();
485        } else {
486            final int bottomSelectionPixel = getBottomSelectionPixel(childrenBottom,
487                    fadingEdgeLength, numColumns, rowStart);
488            final int offset = bottomSelectionPixel - referenceView.getBottom();
489            offsetChildrenTopAndBottom(offset);
490            fillUp(rowStart - 1, referenceView.getTop() - verticalSpacing);
491            pinToTop(childrenTop);
492            fillDown(rowEnd + numColumns, referenceView.getBottom() + verticalSpacing);
493            adjustViewsUpOrDown();
494        }
495
496        return sel;
497    }
498
499    private void pinToTop(int childrenTop) {
500        if (mFirstPosition == 0) {
501            final int top = getChildAt(0).getTop();
502            final int offset = childrenTop - top;
503            if (offset < 0) {
504                offsetChildrenTopAndBottom(offset);
505            }
506        }
507    }
508
509    private void pinToBottom(int childrenBottom) {
510        final int count = getChildCount();
511        if (mFirstPosition + count == mItemCount) {
512            final int bottom = getChildAt(count - 1).getBottom();
513            final int offset = childrenBottom - bottom;
514            if (offset > 0) {
515                offsetChildrenTopAndBottom(offset);
516            }
517        }
518    }
519
520    @Override
521    int findMotionRow(int y) {
522        final int childCount = getChildCount();
523        if (childCount > 0) {
524
525            final int numColumns = mNumColumns;
526            if (!mStackFromBottom) {
527                for (int i = 0; i < childCount; i += numColumns) {
528                    if (y <= getChildAt(i).getBottom()) {
529                        return mFirstPosition + i;
530                    }
531                }
532            } else {
533                for (int i = childCount - 1; i >= 0; i -= numColumns) {
534                    if (y >= getChildAt(i).getTop()) {
535                        return mFirstPosition + i;
536                    }
537                }
538            }
539        }
540        return INVALID_POSITION;
541    }
542
543    /**
544     * Layout during a scroll that results from tracking motion events. Places
545     * the mMotionPosition view at the offset specified by mMotionViewTop, and
546     * then build surrounding views from there.
547     *
548     * @param position the position at which to start filling
549     * @param top the top of the view at that position
550     * @return The selected view, or null if the selected view is outside the
551     *         visible area.
552     */
553    private View fillSpecific(int position, int top) {
554        final int numColumns = mNumColumns;
555
556        int motionRowStart;
557        int motionRowEnd = -1;
558
559        if (!mStackFromBottom) {
560            motionRowStart = position - (position % numColumns);
561        } else {
562            final int invertedSelection = mItemCount - 1 - position;
563
564            motionRowEnd = mItemCount - 1 - (invertedSelection - (invertedSelection % numColumns));
565            motionRowStart = Math.max(0, motionRowEnd - numColumns + 1);
566        }
567
568        final View temp = makeRow(mStackFromBottom ? motionRowEnd : motionRowStart, top, true);
569
570        // Possibly changed again in fillUp if we add rows above this one.
571        mFirstPosition = motionRowStart;
572
573        final View referenceView = mReferenceView;
574        // We didn't have anything to layout, bail out
575        if (referenceView == null) {
576            return null;
577        }
578
579        final int verticalSpacing = mVerticalSpacing;
580
581        View above;
582        View below;
583
584        if (!mStackFromBottom) {
585            above = fillUp(motionRowStart - numColumns, referenceView.getTop() - verticalSpacing);
586            adjustViewsUpOrDown();
587            below = fillDown(motionRowStart + numColumns, referenceView.getBottom() + verticalSpacing);
588            // Check if we have dragged the bottom of the grid too high
589            final int childCount = getChildCount();
590            if (childCount > 0) {
591                correctTooHigh(numColumns, verticalSpacing, childCount);
592            }
593        } else {
594            below = fillDown(motionRowEnd + numColumns, referenceView.getBottom() + verticalSpacing);
595            adjustViewsUpOrDown();
596            above = fillUp(motionRowStart - 1, referenceView.getTop() - verticalSpacing);
597            // Check if we have dragged the bottom of the grid too high
598            final int childCount = getChildCount();
599            if (childCount > 0) {
600                correctTooLow(numColumns, verticalSpacing, childCount);
601            }
602        }
603
604        if (temp != null) {
605            return temp;
606        } else if (above != null) {
607            return above;
608        } else {
609            return below;
610        }
611    }
612
613    private void correctTooHigh(int numColumns, int verticalSpacing, int childCount) {
614        // First see if the last item is visible
615        final int lastPosition = mFirstPosition + childCount - 1;
616        if (lastPosition == mItemCount - 1 && childCount > 0) {
617            // Get the last child ...
618            final View lastChild = getChildAt(childCount - 1);
619
620            // ... and its bottom edge
621            final int lastBottom = lastChild.getBottom();
622            // This is bottom of our drawable area
623            final int end = (mBottom - mTop) - mListPadding.bottom;
624
625            // This is how far the bottom edge of the last view is from the bottom of the
626            // drawable area
627            int bottomOffset = end - lastBottom;
628
629            final View firstChild = getChildAt(0);
630            final int firstTop = firstChild.getTop();
631
632            // Make sure we are 1) Too high, and 2) Either there are more rows above the
633            // first row or the first row is scrolled off the top of the drawable area
634            if (bottomOffset > 0 && (mFirstPosition > 0 || firstTop < mListPadding.top))  {
635                if (mFirstPosition == 0) {
636                    // Don't pull the top too far down
637                    bottomOffset = Math.min(bottomOffset, mListPadding.top - firstTop);
638                }
639
640                // Move everything down
641                offsetChildrenTopAndBottom(bottomOffset);
642                if (mFirstPosition > 0) {
643                    // Fill the gap that was opened above mFirstPosition with more rows, if
644                    // possible
645                    fillUp(mFirstPosition - (mStackFromBottom ? 1 : numColumns),
646                            firstChild.getTop() - verticalSpacing);
647                    // Close up the remaining gap
648                    adjustViewsUpOrDown();
649                }
650            }
651        }
652    }
653
654    private void correctTooLow(int numColumns, int verticalSpacing, int childCount) {
655        if (mFirstPosition == 0 && childCount > 0) {
656            // Get the first child ...
657            final View firstChild = getChildAt(0);
658
659            // ... and its top edge
660            final int firstTop = firstChild.getTop();
661
662            // This is top of our drawable area
663            final int start = mListPadding.top;
664
665            // This is bottom of our drawable area
666            final int end = (mBottom - mTop) - mListPadding.bottom;
667
668            // This is how far the top edge of the first view is from the top of the
669            // drawable area
670            int topOffset = firstTop - start;
671            final View lastChild = getChildAt(childCount - 1);
672            final int lastBottom = lastChild.getBottom();
673            final int lastPosition = mFirstPosition + childCount - 1;
674
675            // Make sure we are 1) Too low, and 2) Either there are more rows below the
676            // last row or the last row is scrolled off the bottom of the drawable area
677            if (topOffset > 0 && (lastPosition < mItemCount - 1 || lastBottom > end))  {
678                if (lastPosition == mItemCount - 1 ) {
679                    // Don't pull the bottom too far up
680                    topOffset = Math.min(topOffset, lastBottom - end);
681                }
682
683                // Move everything up
684                offsetChildrenTopAndBottom(-topOffset);
685                if (lastPosition < mItemCount - 1) {
686                    // Fill the gap that was opened below the last position with more rows, if
687                    // possible
688                    fillDown(lastPosition + (!mStackFromBottom ? 1 : numColumns),
689                            lastChild.getBottom() + verticalSpacing);
690                    // Close up the remaining gap
691                    adjustViewsUpOrDown();
692                }
693            }
694        }
695    }
696
697    /**
698     * Fills the grid based on positioning the new selection at a specific
699     * location. The selection may be moved so that it does not intersect the
700     * faded edges. The grid is then filled upwards and downwards from there.
701     *
702     * @param selectedTop Where the selected item should be
703     * @param childrenTop Where to start drawing children
704     * @param childrenBottom Last pixel where children can be drawn
705     * @return The view that currently has selection
706     */
707    private View fillFromSelection(int selectedTop, int childrenTop, int childrenBottom) {
708        final int fadingEdgeLength = getVerticalFadingEdgeLength();
709        final int selectedPosition = mSelectedPosition;
710        final int numColumns = mNumColumns;
711        final int verticalSpacing = mVerticalSpacing;
712
713        int rowStart;
714        int rowEnd = -1;
715
716        if (!mStackFromBottom) {
717            rowStart = selectedPosition - (selectedPosition % numColumns);
718        } else {
719            int invertedSelection = mItemCount - 1 - selectedPosition;
720
721            rowEnd = mItemCount - 1 - (invertedSelection - (invertedSelection % numColumns));
722            rowStart = Math.max(0, rowEnd - numColumns + 1);
723        }
724
725        View sel;
726        View referenceView;
727
728        int topSelectionPixel = getTopSelectionPixel(childrenTop, fadingEdgeLength, rowStart);
729        int bottomSelectionPixel = getBottomSelectionPixel(childrenBottom, fadingEdgeLength,
730                numColumns, rowStart);
731
732        sel = makeRow(mStackFromBottom ? rowEnd : rowStart, selectedTop, true);
733        // Possibly changed again in fillUp if we add rows above this one.
734        mFirstPosition = rowStart;
735
736        referenceView = mReferenceView;
737        adjustForTopFadingEdge(referenceView, topSelectionPixel, bottomSelectionPixel);
738        adjustForBottomFadingEdge(referenceView, topSelectionPixel, bottomSelectionPixel);
739
740        if (!mStackFromBottom) {
741            fillUp(rowStart - numColumns, referenceView.getTop() - verticalSpacing);
742            adjustViewsUpOrDown();
743            fillDown(rowStart + numColumns, referenceView.getBottom() + verticalSpacing);
744        } else {
745            fillDown(rowEnd + numColumns, referenceView.getBottom() + verticalSpacing);
746            adjustViewsUpOrDown();
747            fillUp(rowStart - 1, referenceView.getTop() - verticalSpacing);
748        }
749
750
751        return sel;
752    }
753
754    /**
755     * Calculate the bottom-most pixel we can draw the selection into
756     *
757     * @param childrenBottom Bottom pixel were children can be drawn
758     * @param fadingEdgeLength Length of the fading edge in pixels, if present
759     * @param numColumns Number of columns in the grid
760     * @param rowStart The start of the row that will contain the selection
761     * @return The bottom-most pixel we can draw the selection into
762     */
763    private int getBottomSelectionPixel(int childrenBottom, int fadingEdgeLength,
764            int numColumns, int rowStart) {
765        // Last pixel we can draw the selection into
766        int bottomSelectionPixel = childrenBottom;
767        if (rowStart + numColumns - 1 < mItemCount - 1) {
768            bottomSelectionPixel -= fadingEdgeLength;
769        }
770        return bottomSelectionPixel;
771    }
772
773    /**
774     * Calculate the top-most pixel we can draw the selection into
775     *
776     * @param childrenTop Top pixel were children can be drawn
777     * @param fadingEdgeLength Length of the fading edge in pixels, if present
778     * @param rowStart The start of the row that will contain the selection
779     * @return The top-most pixel we can draw the selection into
780     */
781    private int getTopSelectionPixel(int childrenTop, int fadingEdgeLength, int rowStart) {
782        // first pixel we can draw the selection into
783        int topSelectionPixel = childrenTop;
784        if (rowStart > 0) {
785            topSelectionPixel += fadingEdgeLength;
786        }
787        return topSelectionPixel;
788    }
789
790    /**
791     * Move all views upwards so the selected row does not interesect the bottom
792     * fading edge (if necessary).
793     *
794     * @param childInSelectedRow A child in the row that contains the selection
795     * @param topSelectionPixel The topmost pixel we can draw the selection into
796     * @param bottomSelectionPixel The bottommost pixel we can draw the
797     *        selection into
798     */
799    private void adjustForBottomFadingEdge(View childInSelectedRow,
800            int topSelectionPixel, int bottomSelectionPixel) {
801        // Some of the newly selected item extends below the bottom of the
802        // list
803        if (childInSelectedRow.getBottom() > bottomSelectionPixel) {
804
805            // Find space available above the selection into which we can
806            // scroll upwards
807            int spaceAbove = childInSelectedRow.getTop() - topSelectionPixel;
808
809            // Find space required to bring the bottom of the selected item
810            // fully into view
811            int spaceBelow = childInSelectedRow.getBottom() - bottomSelectionPixel;
812            int offset = Math.min(spaceAbove, spaceBelow);
813
814            // Now offset the selected item to get it into view
815            offsetChildrenTopAndBottom(-offset);
816        }
817    }
818
819    /**
820     * Move all views upwards so the selected row does not interesect the top
821     * fading edge (if necessary).
822     *
823     * @param childInSelectedRow A child in the row that contains the selection
824     * @param topSelectionPixel The topmost pixel we can draw the selection into
825     * @param bottomSelectionPixel The bottommost pixel we can draw the
826     *        selection into
827     */
828    private void adjustForTopFadingEdge(View childInSelectedRow,
829            int topSelectionPixel, int bottomSelectionPixel) {
830        // Some of the newly selected item extends above the top of the list
831        if (childInSelectedRow.getTop() < topSelectionPixel) {
832            // Find space required to bring the top of the selected item
833            // fully into view
834            int spaceAbove = topSelectionPixel - childInSelectedRow.getTop();
835
836            // Find space available below the selection into which we can
837            // scroll downwards
838            int spaceBelow = bottomSelectionPixel - childInSelectedRow.getBottom();
839            int offset = Math.min(spaceAbove, spaceBelow);
840
841            // Now offset the selected item to get it into view
842            offsetChildrenTopAndBottom(offset);
843        }
844    }
845
846    /**
847     * Smoothly scroll to the specified adapter position. The view will
848     * scroll such that the indicated position is displayed.
849     * @param position Scroll to this adapter position.
850     */
851    @android.view.RemotableViewMethod
852    public void smoothScrollToPosition(int position) {
853        super.smoothScrollToPosition(position);
854    }
855
856    /**
857     * Smoothly scroll to the specified adapter position offset. The view will
858     * scroll such that the indicated position is displayed.
859     * @param offset The amount to offset from the adapter position to scroll to.
860     */
861    @android.view.RemotableViewMethod
862    public void smoothScrollByOffset(int offset) {
863        super.smoothScrollByOffset(offset);
864    }
865
866    /**
867     * Fills the grid based on positioning the new selection relative to the old
868     * selection. The new selection will be placed at, above, or below the
869     * location of the new selection depending on how the selection is moving.
870     * The selection will then be pinned to the visible part of the screen,
871     * excluding the edges that are faded. The grid is then filled upwards and
872     * downwards from there.
873     *
874     * @param delta Which way we are moving
875     * @param childrenTop Where to start drawing children
876     * @param childrenBottom Last pixel where children can be drawn
877     * @return The view that currently has selection
878     */
879    private View moveSelection(int delta, int childrenTop, int childrenBottom) {
880        final int fadingEdgeLength = getVerticalFadingEdgeLength();
881        final int selectedPosition = mSelectedPosition;
882        final int numColumns = mNumColumns;
883        final int verticalSpacing = mVerticalSpacing;
884
885        int oldRowStart;
886        int rowStart;
887        int rowEnd = -1;
888
889        if (!mStackFromBottom) {
890            oldRowStart = (selectedPosition - delta) - ((selectedPosition - delta) % numColumns);
891
892            rowStart = selectedPosition - (selectedPosition % numColumns);
893        } else {
894            int invertedSelection = mItemCount - 1 - selectedPosition;
895
896            rowEnd = mItemCount - 1 - (invertedSelection - (invertedSelection % numColumns));
897            rowStart = Math.max(0, rowEnd - numColumns + 1);
898
899            invertedSelection = mItemCount - 1 - (selectedPosition - delta);
900            oldRowStart = mItemCount - 1 - (invertedSelection - (invertedSelection % numColumns));
901            oldRowStart = Math.max(0, oldRowStart - numColumns + 1);
902        }
903
904        final int rowDelta = rowStart - oldRowStart;
905
906        final int topSelectionPixel = getTopSelectionPixel(childrenTop, fadingEdgeLength, rowStart);
907        final int bottomSelectionPixel = getBottomSelectionPixel(childrenBottom, fadingEdgeLength,
908                numColumns, rowStart);
909
910        // Possibly changed again in fillUp if we add rows above this one.
911        mFirstPosition = rowStart;
912
913        View sel;
914        View referenceView;
915
916        if (rowDelta > 0) {
917            /*
918             * Case 1: Scrolling down.
919             */
920
921            final int oldBottom = mReferenceViewInSelectedRow == null ? 0 :
922                    mReferenceViewInSelectedRow.getBottom();
923
924            sel = makeRow(mStackFromBottom ? rowEnd : rowStart, oldBottom + verticalSpacing, true);
925            referenceView = mReferenceView;
926
927            adjustForBottomFadingEdge(referenceView, topSelectionPixel, bottomSelectionPixel);
928        } else if (rowDelta < 0) {
929            /*
930             * Case 2: Scrolling up.
931             */
932            final int oldTop = mReferenceViewInSelectedRow == null ?
933                    0 : mReferenceViewInSelectedRow .getTop();
934
935            sel = makeRow(mStackFromBottom ? rowEnd : rowStart, oldTop - verticalSpacing, false);
936            referenceView = mReferenceView;
937
938            adjustForTopFadingEdge(referenceView, topSelectionPixel, bottomSelectionPixel);
939        } else {
940            /*
941             * Keep selection where it was
942             */
943            final int oldTop = mReferenceViewInSelectedRow == null ?
944                    0 : mReferenceViewInSelectedRow .getTop();
945
946            sel = makeRow(mStackFromBottom ? rowEnd : rowStart, oldTop, true);
947            referenceView = mReferenceView;
948        }
949
950        if (!mStackFromBottom) {
951            fillUp(rowStart - numColumns, referenceView.getTop() - verticalSpacing);
952            adjustViewsUpOrDown();
953            fillDown(rowStart + numColumns, referenceView.getBottom() + verticalSpacing);
954        } else {
955            fillDown(rowEnd + numColumns, referenceView.getBottom() + verticalSpacing);
956            adjustViewsUpOrDown();
957            fillUp(rowStart - 1, referenceView.getTop() - verticalSpacing);
958        }
959
960        return sel;
961    }
962
963    private boolean determineColumns(int availableSpace) {
964        final int requestedHorizontalSpacing = mRequestedHorizontalSpacing;
965        final int stretchMode = mStretchMode;
966        final int requestedColumnWidth = mRequestedColumnWidth;
967        boolean didNotInitiallyFit = false;
968
969        if (mRequestedNumColumns == AUTO_FIT) {
970            if (requestedColumnWidth > 0) {
971                // Client told us to pick the number of columns
972                mNumColumns = (availableSpace + requestedHorizontalSpacing) /
973                        (requestedColumnWidth + requestedHorizontalSpacing);
974            } else {
975                // Just make up a number if we don't have enough info
976                mNumColumns = 2;
977            }
978        } else {
979            // We picked the columns
980            mNumColumns = mRequestedNumColumns;
981        }
982
983        if (mNumColumns <= 0) {
984            mNumColumns = 1;
985        }
986
987        switch (stretchMode) {
988        case NO_STRETCH:
989            // Nobody stretches
990            mColumnWidth = requestedColumnWidth;
991            mHorizontalSpacing = requestedHorizontalSpacing;
992            break;
993
994        default:
995            int spaceLeftOver = availableSpace - (mNumColumns * requestedColumnWidth) -
996                    ((mNumColumns - 1) * requestedHorizontalSpacing);
997
998            if (spaceLeftOver < 0) {
999                didNotInitiallyFit = true;
1000            }
1001
1002            switch (stretchMode) {
1003            case STRETCH_COLUMN_WIDTH:
1004                // Stretch the columns
1005                mColumnWidth = requestedColumnWidth + spaceLeftOver / mNumColumns;
1006                mHorizontalSpacing = requestedHorizontalSpacing;
1007                break;
1008
1009            case STRETCH_SPACING:
1010                // Stretch the spacing between columns
1011                mColumnWidth = requestedColumnWidth;
1012                if (mNumColumns > 1) {
1013                    mHorizontalSpacing = requestedHorizontalSpacing +
1014                        spaceLeftOver / (mNumColumns - 1);
1015                } else {
1016                    mHorizontalSpacing = requestedHorizontalSpacing + spaceLeftOver;
1017                }
1018                break;
1019
1020            case STRETCH_SPACING_UNIFORM:
1021                // Stretch the spacing between columns
1022                mColumnWidth = requestedColumnWidth;
1023                if (mNumColumns > 1) {
1024                    mHorizontalSpacing = requestedHorizontalSpacing +
1025                        spaceLeftOver / (mNumColumns + 1);
1026                } else {
1027                    mHorizontalSpacing = requestedHorizontalSpacing + spaceLeftOver;
1028                }
1029                break;
1030            }
1031
1032            break;
1033        }
1034        return didNotInitiallyFit;
1035    }
1036
1037    @Override
1038    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
1039        // Sets up mListPadding
1040        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
1041
1042        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
1043        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
1044        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
1045        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
1046
1047        if (widthMode == MeasureSpec.UNSPECIFIED) {
1048            if (mColumnWidth > 0) {
1049                widthSize = mColumnWidth + mListPadding.left + mListPadding.right;
1050            } else {
1051                widthSize = mListPadding.left + mListPadding.right;
1052            }
1053            widthSize += getVerticalScrollbarWidth();
1054        }
1055
1056        int childWidth = widthSize - mListPadding.left - mListPadding.right;
1057        boolean didNotInitiallyFit = determineColumns(childWidth);
1058
1059        int childHeight = 0;
1060        int childState = 0;
1061
1062        mItemCount = mAdapter == null ? 0 : mAdapter.getCount();
1063        final int count = mItemCount;
1064        if (count > 0) {
1065            final View child = obtainView(0, mIsScrap);
1066
1067            AbsListView.LayoutParams p = (AbsListView.LayoutParams) child.getLayoutParams();
1068            if (p == null) {
1069                p = (AbsListView.LayoutParams) generateDefaultLayoutParams();
1070                child.setLayoutParams(p);
1071            }
1072            p.viewType = mAdapter.getItemViewType(0);
1073            p.isEnabled = mAdapter.isEnabled(0);
1074            p.forceAdd = true;
1075
1076            int childHeightSpec = getChildMeasureSpec(
1077                    MeasureSpec.makeSafeMeasureSpec(MeasureSpec.getSize(heightMeasureSpec),
1078                            MeasureSpec.UNSPECIFIED), 0, p.height);
1079            int childWidthSpec = getChildMeasureSpec(
1080                    MeasureSpec.makeMeasureSpec(mColumnWidth, MeasureSpec.EXACTLY), 0, p.width);
1081            child.measure(childWidthSpec, childHeightSpec);
1082
1083            childHeight = child.getMeasuredHeight();
1084            childState = combineMeasuredStates(childState, child.getMeasuredState());
1085
1086            if (mRecycler.shouldRecycleViewType(p.viewType)) {
1087                mRecycler.addScrapView(child, -1);
1088            }
1089        }
1090
1091        if (heightMode == MeasureSpec.UNSPECIFIED) {
1092            heightSize = mListPadding.top + mListPadding.bottom + childHeight +
1093                    getVerticalFadingEdgeLength() * 2;
1094        }
1095
1096        if (heightMode == MeasureSpec.AT_MOST) {
1097            int ourSize =  mListPadding.top + mListPadding.bottom;
1098
1099            final int numColumns = mNumColumns;
1100            for (int i = 0; i < count; i += numColumns) {
1101                ourSize += childHeight;
1102                if (i + numColumns < count) {
1103                    ourSize += mVerticalSpacing;
1104                }
1105                if (ourSize >= heightSize) {
1106                    ourSize = heightSize;
1107                    break;
1108                }
1109            }
1110            heightSize = ourSize;
1111        }
1112
1113        if (widthMode == MeasureSpec.AT_MOST && mRequestedNumColumns != AUTO_FIT) {
1114            int ourSize = (mRequestedNumColumns*mColumnWidth)
1115                    + ((mRequestedNumColumns-1)*mHorizontalSpacing)
1116                    + mListPadding.left + mListPadding.right;
1117            if (ourSize > widthSize || didNotInitiallyFit) {
1118                widthSize |= MEASURED_STATE_TOO_SMALL;
1119            }
1120        }
1121
1122        setMeasuredDimension(widthSize, heightSize);
1123        mWidthMeasureSpec = widthMeasureSpec;
1124    }
1125
1126    @Override
1127    protected void attachLayoutAnimationParameters(View child,
1128            ViewGroup.LayoutParams params, int index, int count) {
1129
1130        GridLayoutAnimationController.AnimationParameters animationParams =
1131                (GridLayoutAnimationController.AnimationParameters) params.layoutAnimationParameters;
1132
1133        if (animationParams == null) {
1134            animationParams = new GridLayoutAnimationController.AnimationParameters();
1135            params.layoutAnimationParameters = animationParams;
1136        }
1137
1138        animationParams.count = count;
1139        animationParams.index = index;
1140        animationParams.columnsCount = mNumColumns;
1141        animationParams.rowsCount = count / mNumColumns;
1142
1143        if (!mStackFromBottom) {
1144            animationParams.column = index % mNumColumns;
1145            animationParams.row = index / mNumColumns;
1146        } else {
1147            final int invertedIndex = count - 1 - index;
1148
1149            animationParams.column = mNumColumns - 1 - (invertedIndex % mNumColumns);
1150            animationParams.row = animationParams.rowsCount - 1 - invertedIndex / mNumColumns;
1151        }
1152    }
1153
1154    @Override
1155    protected void layoutChildren() {
1156        final boolean blockLayoutRequests = mBlockLayoutRequests;
1157        if (!blockLayoutRequests) {
1158            mBlockLayoutRequests = true;
1159        }
1160
1161        try {
1162            super.layoutChildren();
1163
1164            invalidate();
1165
1166            if (mAdapter == null) {
1167                resetList();
1168                invokeOnItemScrollListener();
1169                return;
1170            }
1171
1172            final int childrenTop = mListPadding.top;
1173            final int childrenBottom = mBottom - mTop - mListPadding.bottom;
1174
1175            int childCount = getChildCount();
1176            int index;
1177            int delta = 0;
1178
1179            View sel;
1180            View oldSel = null;
1181            View oldFirst = null;
1182            View newSel = null;
1183
1184            // Remember stuff we will need down below
1185            switch (mLayoutMode) {
1186            case LAYOUT_SET_SELECTION:
1187                index = mNextSelectedPosition - mFirstPosition;
1188                if (index >= 0 && index < childCount) {
1189                    newSel = getChildAt(index);
1190                }
1191                break;
1192            case LAYOUT_FORCE_TOP:
1193            case LAYOUT_FORCE_BOTTOM:
1194            case LAYOUT_SPECIFIC:
1195            case LAYOUT_SYNC:
1196                break;
1197            case LAYOUT_MOVE_SELECTION:
1198                if (mNextSelectedPosition >= 0) {
1199                    delta = mNextSelectedPosition - mSelectedPosition;
1200                }
1201                break;
1202            default:
1203                // Remember the previously selected view
1204                index = mSelectedPosition - mFirstPosition;
1205                if (index >= 0 && index < childCount) {
1206                    oldSel = getChildAt(index);
1207                }
1208
1209                // Remember the previous first child
1210                oldFirst = getChildAt(0);
1211            }
1212
1213            boolean dataChanged = mDataChanged;
1214            if (dataChanged) {
1215                handleDataChanged();
1216            }
1217
1218            // Handle the empty set by removing all views that are visible
1219            // and calling it a day
1220            if (mItemCount == 0) {
1221                resetList();
1222                invokeOnItemScrollListener();
1223                return;
1224            }
1225
1226            setSelectedPositionInt(mNextSelectedPosition);
1227
1228            AccessibilityNodeInfo accessibilityFocusLayoutRestoreNode = null;
1229            View accessibilityFocusLayoutRestoreView = null;
1230            int accessibilityFocusPosition = INVALID_POSITION;
1231
1232            // Remember which child, if any, had accessibility focus. This must
1233            // occur before recycling any views, since that will clear
1234            // accessibility focus.
1235            final ViewRootImpl viewRootImpl = getViewRootImpl();
1236            if (viewRootImpl != null) {
1237                final View focusHost = viewRootImpl.getAccessibilityFocusedHost();
1238                if (focusHost != null) {
1239                    final View focusChild = getAccessibilityFocusedChild(focusHost);
1240                    if (focusChild != null) {
1241                        if (!dataChanged || focusChild.hasTransientState()
1242                                || mAdapterHasStableIds) {
1243                            // The views won't be changing, so try to maintain
1244                            // focus on the current host and virtual view.
1245                            accessibilityFocusLayoutRestoreView = focusHost;
1246                            accessibilityFocusLayoutRestoreNode = viewRootImpl
1247                                    .getAccessibilityFocusedVirtualView();
1248                        }
1249
1250                        // Try to maintain focus at the same position.
1251                        accessibilityFocusPosition = getPositionForView(focusChild);
1252                    }
1253                }
1254            }
1255
1256            // Pull all children into the RecycleBin.
1257            // These views will be reused if possible
1258            final int firstPosition = mFirstPosition;
1259            final RecycleBin recycleBin = mRecycler;
1260
1261            if (dataChanged) {
1262                for (int i = 0; i < childCount; i++) {
1263                    recycleBin.addScrapView(getChildAt(i), firstPosition+i);
1264                }
1265            } else {
1266                recycleBin.fillActiveViews(childCount, firstPosition);
1267            }
1268
1269            // Clear out old views
1270            detachAllViewsFromParent();
1271            recycleBin.removeSkippedScrap();
1272
1273            switch (mLayoutMode) {
1274            case LAYOUT_SET_SELECTION:
1275                if (newSel != null) {
1276                    sel = fillFromSelection(newSel.getTop(), childrenTop, childrenBottom);
1277                } else {
1278                    sel = fillSelection(childrenTop, childrenBottom);
1279                }
1280                break;
1281            case LAYOUT_FORCE_TOP:
1282                mFirstPosition = 0;
1283                sel = fillFromTop(childrenTop);
1284                adjustViewsUpOrDown();
1285                break;
1286            case LAYOUT_FORCE_BOTTOM:
1287                sel = fillUp(mItemCount - 1, childrenBottom);
1288                adjustViewsUpOrDown();
1289                break;
1290            case LAYOUT_SPECIFIC:
1291                sel = fillSpecific(mSelectedPosition, mSpecificTop);
1292                break;
1293            case LAYOUT_SYNC:
1294                sel = fillSpecific(mSyncPosition, mSpecificTop);
1295                break;
1296            case LAYOUT_MOVE_SELECTION:
1297                // Move the selection relative to its old position
1298                sel = moveSelection(delta, childrenTop, childrenBottom);
1299                break;
1300            default:
1301                if (childCount == 0) {
1302                    if (!mStackFromBottom) {
1303                        setSelectedPositionInt(mAdapter == null || isInTouchMode() ?
1304                                INVALID_POSITION : 0);
1305                        sel = fillFromTop(childrenTop);
1306                    } else {
1307                        final int last = mItemCount - 1;
1308                        setSelectedPositionInt(mAdapter == null || isInTouchMode() ?
1309                                INVALID_POSITION : last);
1310                        sel = fillFromBottom(last, childrenBottom);
1311                    }
1312                } else {
1313                    if (mSelectedPosition >= 0 && mSelectedPosition < mItemCount) {
1314                        sel = fillSpecific(mSelectedPosition, oldSel == null ?
1315                                childrenTop : oldSel.getTop());
1316                    } else if (mFirstPosition < mItemCount)  {
1317                        sel = fillSpecific(mFirstPosition, oldFirst == null ?
1318                                childrenTop : oldFirst.getTop());
1319                    } else {
1320                        sel = fillSpecific(0, childrenTop);
1321                    }
1322                }
1323                break;
1324            }
1325
1326            // Flush any cached views that did not get reused above
1327            recycleBin.scrapActiveViews();
1328
1329            if (sel != null) {
1330               positionSelector(INVALID_POSITION, sel);
1331               mSelectedTop = sel.getTop();
1332            } else {
1333                final boolean inTouchMode = mTouchMode > TOUCH_MODE_DOWN
1334                        && mTouchMode < TOUCH_MODE_SCROLL;
1335                if (inTouchMode) {
1336                    // If the user's finger is down, select the motion position.
1337                    final View child = getChildAt(mMotionPosition - mFirstPosition);
1338                    if (child != null) {
1339                        positionSelector(mMotionPosition, child);
1340                    }
1341                } else if (mSelectedPosition != INVALID_POSITION) {
1342                    // If we had previously positioned the selector somewhere,
1343                    // put it back there. It might not match up with the data,
1344                    // but it's transitioning out so it's not a big deal.
1345                    final View child = getChildAt(mSelectorPosition - mFirstPosition);
1346                    if (child != null) {
1347                        positionSelector(mSelectorPosition, child);
1348                    }
1349                } else {
1350                    // Otherwise, clear selection.
1351                    mSelectedTop = 0;
1352                    mSelectorRect.setEmpty();
1353                }
1354            }
1355
1356            // Attempt to restore accessibility focus, if necessary.
1357            if (viewRootImpl != null) {
1358                final View newAccessibilityFocusedView = viewRootImpl.getAccessibilityFocusedHost();
1359                if (newAccessibilityFocusedView == null) {
1360                    if (accessibilityFocusLayoutRestoreView != null
1361                            && accessibilityFocusLayoutRestoreView.isAttachedToWindow()) {
1362                        final AccessibilityNodeProvider provider =
1363                                accessibilityFocusLayoutRestoreView.getAccessibilityNodeProvider();
1364                        if (accessibilityFocusLayoutRestoreNode != null && provider != null) {
1365                            final int virtualViewId = AccessibilityNodeInfo.getVirtualDescendantId(
1366                                    accessibilityFocusLayoutRestoreNode.getSourceNodeId());
1367                            provider.performAction(virtualViewId,
1368                                    AccessibilityNodeInfo.ACTION_ACCESSIBILITY_FOCUS, null);
1369                        } else {
1370                            accessibilityFocusLayoutRestoreView.requestAccessibilityFocus();
1371                        }
1372                    } else if (accessibilityFocusPosition != INVALID_POSITION) {
1373                        // Bound the position within the visible children.
1374                        final int position = MathUtils.constrain(
1375                                accessibilityFocusPosition - mFirstPosition, 0,
1376                                getChildCount() - 1);
1377                        final View restoreView = getChildAt(position);
1378                        if (restoreView != null) {
1379                            restoreView.requestAccessibilityFocus();
1380                        }
1381                    }
1382                }
1383            }
1384
1385            mLayoutMode = LAYOUT_NORMAL;
1386            mDataChanged = false;
1387            if (mPositionScrollAfterLayout != null) {
1388                post(mPositionScrollAfterLayout);
1389                mPositionScrollAfterLayout = null;
1390            }
1391            mNeedSync = false;
1392            setNextSelectedPositionInt(mSelectedPosition);
1393
1394            updateScrollIndicators();
1395
1396            if (mItemCount > 0) {
1397                checkSelectionChanged();
1398            }
1399
1400            invokeOnItemScrollListener();
1401        } finally {
1402            if (!blockLayoutRequests) {
1403                mBlockLayoutRequests = false;
1404            }
1405        }
1406    }
1407
1408
1409    /**
1410     * Obtain the view and add it to our list of children. The view can be made
1411     * fresh, converted from an unused view, or used as is if it was in the
1412     * recycle bin.
1413     *
1414     * @param position Logical position in the list
1415     * @param y Top or bottom edge of the view to add
1416     * @param flow if true, align top edge to y. If false, align bottom edge to
1417     *        y.
1418     * @param childrenLeft Left edge where children should be positioned
1419     * @param selected Is this position selected?
1420     * @param where to add new item in the list
1421     * @return View that was added
1422     */
1423    private View makeAndAddView(int position, int y, boolean flow, int childrenLeft,
1424            boolean selected, int where) {
1425        View child;
1426
1427        if (!mDataChanged) {
1428            // Try to use an existing view for this position
1429            child = mRecycler.getActiveView(position);
1430            if (child != null) {
1431                // Found it -- we're using an existing child
1432                // This just needs to be positioned
1433                setupChild(child, position, y, flow, childrenLeft, selected, true, where);
1434                return child;
1435            }
1436        }
1437
1438        // Make a new view for this position, or convert an unused view if
1439        // possible
1440        child = obtainView(position, mIsScrap);
1441
1442        // This needs to be positioned and measured
1443        setupChild(child, position, y, flow, childrenLeft, selected, mIsScrap[0], where);
1444
1445        return child;
1446    }
1447
1448    /**
1449     * Add a view as a child and make sure it is measured (if necessary) and
1450     * positioned properly.
1451     *
1452     * @param child The view to add
1453     * @param position The position of the view
1454     * @param y The y position relative to which this view will be positioned
1455     * @param flow if true, align top edge to y. If false, align bottom edge
1456     *        to y.
1457     * @param childrenLeft Left edge where children should be positioned
1458     * @param selected Is this position selected?
1459     * @param recycled Has this view been pulled from the recycle bin? If so it
1460     *        does not need to be remeasured.
1461     * @param where Where to add the item in the list
1462     *
1463     */
1464    private void setupChild(View child, int position, int y, boolean flow, int childrenLeft,
1465            boolean selected, boolean recycled, int where) {
1466        Trace.traceBegin(Trace.TRACE_TAG_VIEW, "setupGridItem");
1467
1468        boolean isSelected = selected && shouldShowSelector();
1469        final boolean updateChildSelected = isSelected != child.isSelected();
1470        final int mode = mTouchMode;
1471        final boolean isPressed = mode > TOUCH_MODE_DOWN && mode < TOUCH_MODE_SCROLL &&
1472                mMotionPosition == position;
1473        final boolean updateChildPressed = isPressed != child.isPressed();
1474
1475        boolean needToMeasure = !recycled || updateChildSelected || child.isLayoutRequested();
1476
1477        // Respect layout params that are already in the view. Otherwise make
1478        // some up...
1479        AbsListView.LayoutParams p = (AbsListView.LayoutParams) child.getLayoutParams();
1480        if (p == null) {
1481            p = (AbsListView.LayoutParams) generateDefaultLayoutParams();
1482        }
1483        p.viewType = mAdapter.getItemViewType(position);
1484        p.isEnabled = mAdapter.isEnabled(position);
1485
1486        if (recycled && !p.forceAdd) {
1487            attachViewToParent(child, where, p);
1488        } else {
1489            p.forceAdd = false;
1490            addViewInLayout(child, where, p, true);
1491        }
1492
1493        if (updateChildSelected) {
1494            child.setSelected(isSelected);
1495            if (isSelected) {
1496                requestFocus();
1497            }
1498        }
1499
1500        if (updateChildPressed) {
1501            child.setPressed(isPressed);
1502        }
1503
1504        if (mChoiceMode != CHOICE_MODE_NONE && mCheckStates != null) {
1505            if (child instanceof Checkable) {
1506                ((Checkable) child).setChecked(mCheckStates.get(position));
1507            } else if (getContext().getApplicationInfo().targetSdkVersion
1508                    >= android.os.Build.VERSION_CODES.HONEYCOMB) {
1509                child.setActivated(mCheckStates.get(position));
1510            }
1511        }
1512
1513        if (needToMeasure) {
1514            int childHeightSpec = ViewGroup.getChildMeasureSpec(
1515                    MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), 0, p.height);
1516
1517            int childWidthSpec = ViewGroup.getChildMeasureSpec(
1518                    MeasureSpec.makeMeasureSpec(mColumnWidth, MeasureSpec.EXACTLY), 0, p.width);
1519            child.measure(childWidthSpec, childHeightSpec);
1520        } else {
1521            cleanupLayoutState(child);
1522        }
1523
1524        final int w = child.getMeasuredWidth();
1525        final int h = child.getMeasuredHeight();
1526
1527        int childLeft;
1528        final int childTop = flow ? y : y - h;
1529
1530        final int layoutDirection = getLayoutDirection();
1531        final int absoluteGravity = Gravity.getAbsoluteGravity(mGravity, layoutDirection);
1532        switch (absoluteGravity & Gravity.HORIZONTAL_GRAVITY_MASK) {
1533            case Gravity.LEFT:
1534                childLeft = childrenLeft;
1535                break;
1536            case Gravity.CENTER_HORIZONTAL:
1537                childLeft = childrenLeft + ((mColumnWidth - w) / 2);
1538                break;
1539            case Gravity.RIGHT:
1540                childLeft = childrenLeft + mColumnWidth - w;
1541                break;
1542            default:
1543                childLeft = childrenLeft;
1544                break;
1545        }
1546
1547        if (needToMeasure) {
1548            final int childRight = childLeft + w;
1549            final int childBottom = childTop + h;
1550            child.layout(childLeft, childTop, childRight, childBottom);
1551        } else {
1552            child.offsetLeftAndRight(childLeft - child.getLeft());
1553            child.offsetTopAndBottom(childTop - child.getTop());
1554        }
1555
1556        if (mCachingStarted) {
1557            child.setDrawingCacheEnabled(true);
1558        }
1559
1560        if (recycled && (((AbsListView.LayoutParams)child.getLayoutParams()).scrappedFromPosition)
1561                != position) {
1562            child.jumpDrawablesToCurrentState();
1563        }
1564
1565        Trace.traceEnd(Trace.TRACE_TAG_VIEW);
1566    }
1567
1568    /**
1569     * Sets the currently selected item
1570     *
1571     * @param position Index (starting at 0) of the data item to be selected.
1572     *
1573     * If in touch mode, the item will not be selected but it will still be positioned
1574     * appropriately.
1575     */
1576    @Override
1577    public void setSelection(int position) {
1578        if (!isInTouchMode()) {
1579            setNextSelectedPositionInt(position);
1580        } else {
1581            mResurrectToPosition = position;
1582        }
1583        mLayoutMode = LAYOUT_SET_SELECTION;
1584        if (mPositionScroller != null) {
1585            mPositionScroller.stop();
1586        }
1587        requestLayout();
1588    }
1589
1590    /**
1591     * Makes the item at the supplied position selected.
1592     *
1593     * @param position the position of the new selection
1594     */
1595    @Override
1596    void setSelectionInt(int position) {
1597        int previousSelectedPosition = mNextSelectedPosition;
1598
1599        if (mPositionScroller != null) {
1600            mPositionScroller.stop();
1601        }
1602
1603        setNextSelectedPositionInt(position);
1604        layoutChildren();
1605
1606        final int next = mStackFromBottom ? mItemCount - 1  - mNextSelectedPosition :
1607            mNextSelectedPosition;
1608        final int previous = mStackFromBottom ? mItemCount - 1
1609                - previousSelectedPosition : previousSelectedPosition;
1610
1611        final int nextRow = next / mNumColumns;
1612        final int previousRow = previous / mNumColumns;
1613
1614        if (nextRow != previousRow) {
1615            awakenScrollBars();
1616        }
1617
1618    }
1619
1620    @Override
1621    public boolean onKeyDown(int keyCode, KeyEvent event) {
1622        return commonKey(keyCode, 1, event);
1623    }
1624
1625    @Override
1626    public boolean onKeyMultiple(int keyCode, int repeatCount, KeyEvent event) {
1627        return commonKey(keyCode, repeatCount, event);
1628    }
1629
1630    @Override
1631    public boolean onKeyUp(int keyCode, KeyEvent event) {
1632        return commonKey(keyCode, 1, event);
1633    }
1634
1635    private boolean commonKey(int keyCode, int count, KeyEvent event) {
1636        if (mAdapter == null) {
1637            return false;
1638        }
1639
1640        if (mDataChanged) {
1641            layoutChildren();
1642        }
1643
1644        boolean handled = false;
1645        int action = event.getAction();
1646        if (KeyEvent.isConfirmKey(keyCode)
1647                && event.hasNoModifiers() && action != KeyEvent.ACTION_UP) {
1648            handled = resurrectSelectionIfNeeded();
1649            if (!handled && event.getRepeatCount() == 0 && getChildCount() > 0) {
1650                keyPressed();
1651                handled = true;
1652            }
1653        }
1654
1655        if (!handled && action != KeyEvent.ACTION_UP) {
1656            switch (keyCode) {
1657                case KeyEvent.KEYCODE_DPAD_LEFT:
1658                    if (event.hasNoModifiers()) {
1659                        handled = resurrectSelectionIfNeeded() || arrowScroll(FOCUS_LEFT);
1660                    }
1661                    break;
1662
1663                case KeyEvent.KEYCODE_DPAD_RIGHT:
1664                    if (event.hasNoModifiers()) {
1665                        handled = resurrectSelectionIfNeeded() || arrowScroll(FOCUS_RIGHT);
1666                    }
1667                    break;
1668
1669                case KeyEvent.KEYCODE_DPAD_UP:
1670                    if (event.hasNoModifiers()) {
1671                        handled = resurrectSelectionIfNeeded() || arrowScroll(FOCUS_UP);
1672                    } else if (event.hasModifiers(KeyEvent.META_ALT_ON)) {
1673                        handled = resurrectSelectionIfNeeded() || fullScroll(FOCUS_UP);
1674                    }
1675                    break;
1676
1677                case KeyEvent.KEYCODE_DPAD_DOWN:
1678                    if (event.hasNoModifiers()) {
1679                        handled = resurrectSelectionIfNeeded() || arrowScroll(FOCUS_DOWN);
1680                    } else if (event.hasModifiers(KeyEvent.META_ALT_ON)) {
1681                        handled = resurrectSelectionIfNeeded() || fullScroll(FOCUS_DOWN);
1682                    }
1683                    break;
1684
1685                case KeyEvent.KEYCODE_PAGE_UP:
1686                    if (event.hasNoModifiers()) {
1687                        handled = resurrectSelectionIfNeeded() || pageScroll(FOCUS_UP);
1688                    } else if (event.hasModifiers(KeyEvent.META_ALT_ON)) {
1689                        handled = resurrectSelectionIfNeeded() || fullScroll(FOCUS_UP);
1690                    }
1691                    break;
1692
1693                case KeyEvent.KEYCODE_PAGE_DOWN:
1694                    if (event.hasNoModifiers()) {
1695                        handled = resurrectSelectionIfNeeded() || pageScroll(FOCUS_DOWN);
1696                    } else if (event.hasModifiers(KeyEvent.META_ALT_ON)) {
1697                        handled = resurrectSelectionIfNeeded() || fullScroll(FOCUS_DOWN);
1698                    }
1699                    break;
1700
1701                case KeyEvent.KEYCODE_MOVE_HOME:
1702                    if (event.hasNoModifiers()) {
1703                        handled = resurrectSelectionIfNeeded() || fullScroll(FOCUS_UP);
1704                    }
1705                    break;
1706
1707                case KeyEvent.KEYCODE_MOVE_END:
1708                    if (event.hasNoModifiers()) {
1709                        handled = resurrectSelectionIfNeeded() || fullScroll(FOCUS_DOWN);
1710                    }
1711                    break;
1712
1713                case KeyEvent.KEYCODE_TAB:
1714                    // XXX Sometimes it is useful to be able to TAB through the items in
1715                    //     a GridView sequentially.  Unfortunately this can create an
1716                    //     asymmetry in TAB navigation order unless the list selection
1717                    //     always reverts to the top or bottom when receiving TAB focus from
1718                    //     another widget.  Leaving this behavior disabled for now but
1719                    //     perhaps it should be configurable (and more comprehensive).
1720                    if (false) {
1721                        if (event.hasNoModifiers()) {
1722                            handled = resurrectSelectionIfNeeded()
1723                                    || sequenceScroll(FOCUS_FORWARD);
1724                        } else if (event.hasModifiers(KeyEvent.META_SHIFT_ON)) {
1725                            handled = resurrectSelectionIfNeeded()
1726                                    || sequenceScroll(FOCUS_BACKWARD);
1727                        }
1728                    }
1729                    break;
1730            }
1731        }
1732
1733        if (handled) {
1734            return true;
1735        }
1736
1737        if (sendToTextFilter(keyCode, count, event)) {
1738            return true;
1739        }
1740
1741        switch (action) {
1742            case KeyEvent.ACTION_DOWN:
1743                return super.onKeyDown(keyCode, event);
1744            case KeyEvent.ACTION_UP:
1745                return super.onKeyUp(keyCode, event);
1746            case KeyEvent.ACTION_MULTIPLE:
1747                return super.onKeyMultiple(keyCode, count, event);
1748            default:
1749                return false;
1750        }
1751    }
1752
1753    /**
1754     * Scrolls up or down by the number of items currently present on screen.
1755     *
1756     * @param direction either {@link View#FOCUS_UP} or {@link View#FOCUS_DOWN}
1757     * @return whether selection was moved
1758     */
1759    boolean pageScroll(int direction) {
1760        int nextPage = -1;
1761
1762        if (direction == FOCUS_UP) {
1763            nextPage = Math.max(0, mSelectedPosition - getChildCount());
1764        } else if (direction == FOCUS_DOWN) {
1765            nextPage = Math.min(mItemCount - 1, mSelectedPosition + getChildCount());
1766        }
1767
1768        if (nextPage >= 0) {
1769            setSelectionInt(nextPage);
1770            invokeOnItemScrollListener();
1771            awakenScrollBars();
1772            return true;
1773        }
1774
1775        return false;
1776    }
1777
1778    /**
1779     * Go to the last or first item if possible.
1780     *
1781     * @param direction either {@link View#FOCUS_UP} or {@link View#FOCUS_DOWN}.
1782     *
1783     * @return Whether selection was moved.
1784     */
1785    boolean fullScroll(int direction) {
1786        boolean moved = false;
1787        if (direction == FOCUS_UP) {
1788            mLayoutMode = LAYOUT_SET_SELECTION;
1789            setSelectionInt(0);
1790            invokeOnItemScrollListener();
1791            moved = true;
1792        } else if (direction == FOCUS_DOWN) {
1793            mLayoutMode = LAYOUT_SET_SELECTION;
1794            setSelectionInt(mItemCount - 1);
1795            invokeOnItemScrollListener();
1796            moved = true;
1797        }
1798
1799        if (moved) {
1800            awakenScrollBars();
1801        }
1802
1803        return moved;
1804    }
1805
1806    /**
1807     * Scrolls to the next or previous item, horizontally or vertically.
1808     *
1809     * @param direction either {@link View#FOCUS_LEFT}, {@link View#FOCUS_RIGHT},
1810     *        {@link View#FOCUS_UP} or {@link View#FOCUS_DOWN}
1811     *
1812     * @return whether selection was moved
1813     */
1814    boolean arrowScroll(int direction) {
1815        final int selectedPosition = mSelectedPosition;
1816        final int numColumns = mNumColumns;
1817
1818        int startOfRowPos;
1819        int endOfRowPos;
1820
1821        boolean moved = false;
1822
1823        if (!mStackFromBottom) {
1824            startOfRowPos = (selectedPosition / numColumns) * numColumns;
1825            endOfRowPos = Math.min(startOfRowPos + numColumns - 1, mItemCount - 1);
1826        } else {
1827            final int invertedSelection = mItemCount - 1 - selectedPosition;
1828            endOfRowPos = mItemCount - 1 - (invertedSelection / numColumns) * numColumns;
1829            startOfRowPos = Math.max(0, endOfRowPos - numColumns + 1);
1830        }
1831
1832        switch (direction) {
1833            case FOCUS_UP:
1834                if (startOfRowPos > 0) {
1835                    mLayoutMode = LAYOUT_MOVE_SELECTION;
1836                    setSelectionInt(Math.max(0, selectedPosition - numColumns));
1837                    moved = true;
1838                }
1839                break;
1840            case FOCUS_DOWN:
1841                if (endOfRowPos < mItemCount - 1) {
1842                    mLayoutMode = LAYOUT_MOVE_SELECTION;
1843                    setSelectionInt(Math.min(selectedPosition + numColumns, mItemCount - 1));
1844                    moved = true;
1845                }
1846                break;
1847        }
1848
1849        final boolean isLayoutRtl = isLayoutRtl();
1850        if (selectedPosition > startOfRowPos && ((direction == FOCUS_LEFT && !isLayoutRtl) ||
1851                (direction == FOCUS_RIGHT && isLayoutRtl))) {
1852            mLayoutMode = LAYOUT_MOVE_SELECTION;
1853            setSelectionInt(Math.max(0, selectedPosition - 1));
1854            moved = true;
1855        } else if (selectedPosition < endOfRowPos && ((direction == FOCUS_LEFT && isLayoutRtl) ||
1856                (direction == FOCUS_RIGHT && !isLayoutRtl))) {
1857            mLayoutMode = LAYOUT_MOVE_SELECTION;
1858            setSelectionInt(Math.min(selectedPosition + 1, mItemCount - 1));
1859            moved = true;
1860        }
1861
1862        if (moved) {
1863            playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));
1864            invokeOnItemScrollListener();
1865        }
1866
1867        if (moved) {
1868            awakenScrollBars();
1869        }
1870
1871        return moved;
1872    }
1873
1874    /**
1875     * Goes to the next or previous item according to the order set by the
1876     * adapter.
1877     */
1878    boolean sequenceScroll(int direction) {
1879        int selectedPosition = mSelectedPosition;
1880        int numColumns = mNumColumns;
1881        int count = mItemCount;
1882
1883        int startOfRow;
1884        int endOfRow;
1885        if (!mStackFromBottom) {
1886            startOfRow = (selectedPosition / numColumns) * numColumns;
1887            endOfRow = Math.min(startOfRow + numColumns - 1, count - 1);
1888        } else {
1889            int invertedSelection = count - 1 - selectedPosition;
1890            endOfRow = count - 1 - (invertedSelection / numColumns) * numColumns;
1891            startOfRow = Math.max(0, endOfRow - numColumns + 1);
1892        }
1893
1894        boolean moved = false;
1895        boolean showScroll = false;
1896        switch (direction) {
1897            case FOCUS_FORWARD:
1898                if (selectedPosition < count - 1) {
1899                    // Move to the next item.
1900                    mLayoutMode = LAYOUT_MOVE_SELECTION;
1901                    setSelectionInt(selectedPosition + 1);
1902                    moved = true;
1903                    // Show the scrollbar only if changing rows.
1904                    showScroll = selectedPosition == endOfRow;
1905                }
1906                break;
1907
1908            case FOCUS_BACKWARD:
1909                if (selectedPosition > 0) {
1910                    // Move to the previous item.
1911                    mLayoutMode = LAYOUT_MOVE_SELECTION;
1912                    setSelectionInt(selectedPosition - 1);
1913                    moved = true;
1914                    // Show the scrollbar only if changing rows.
1915                    showScroll = selectedPosition == startOfRow;
1916                }
1917                break;
1918        }
1919
1920        if (moved) {
1921            playSoundEffect(SoundEffectConstants.getContantForFocusDirection(direction));
1922            invokeOnItemScrollListener();
1923        }
1924
1925        if (showScroll) {
1926            awakenScrollBars();
1927        }
1928
1929        return moved;
1930    }
1931
1932    @Override
1933    protected void onFocusChanged(boolean gainFocus, int direction, Rect previouslyFocusedRect) {
1934        super.onFocusChanged(gainFocus, direction, previouslyFocusedRect);
1935
1936        int closestChildIndex = -1;
1937        if (gainFocus && previouslyFocusedRect != null) {
1938            previouslyFocusedRect.offset(mScrollX, mScrollY);
1939
1940            // figure out which item should be selected based on previously
1941            // focused rect
1942            Rect otherRect = mTempRect;
1943            int minDistance = Integer.MAX_VALUE;
1944            final int childCount = getChildCount();
1945            for (int i = 0; i < childCount; i++) {
1946                // only consider view's on appropriate edge of grid
1947                if (!isCandidateSelection(i, direction)) {
1948                    continue;
1949                }
1950
1951                final View other = getChildAt(i);
1952                other.getDrawingRect(otherRect);
1953                offsetDescendantRectToMyCoords(other, otherRect);
1954                int distance = getDistance(previouslyFocusedRect, otherRect, direction);
1955
1956                if (distance < minDistance) {
1957                    minDistance = distance;
1958                    closestChildIndex = i;
1959                }
1960            }
1961        }
1962
1963        if (closestChildIndex >= 0) {
1964            setSelection(closestChildIndex + mFirstPosition);
1965        } else {
1966            requestLayout();
1967        }
1968    }
1969
1970    /**
1971     * Is childIndex a candidate for next focus given the direction the focus
1972     * change is coming from?
1973     * @param childIndex The index to check.
1974     * @param direction The direction, one of
1975     *        {FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT, FOCUS_FORWARD, FOCUS_BACKWARD}
1976     * @return Whether childIndex is a candidate.
1977     */
1978    private boolean isCandidateSelection(int childIndex, int direction) {
1979        final int count = getChildCount();
1980        final int invertedIndex = count - 1 - childIndex;
1981
1982        int rowStart;
1983        int rowEnd;
1984
1985        if (!mStackFromBottom) {
1986            rowStart = childIndex - (childIndex % mNumColumns);
1987            rowEnd = Math.max(rowStart + mNumColumns - 1, count);
1988        } else {
1989            rowEnd = count - 1 - (invertedIndex - (invertedIndex % mNumColumns));
1990            rowStart = Math.max(0, rowEnd - mNumColumns + 1);
1991        }
1992
1993        switch (direction) {
1994            case View.FOCUS_RIGHT:
1995                // coming from left, selection is only valid if it is on left
1996                // edge
1997                return childIndex == rowStart;
1998            case View.FOCUS_DOWN:
1999                // coming from top; only valid if in top row
2000                return rowStart == 0;
2001            case View.FOCUS_LEFT:
2002                // coming from right, must be on right edge
2003                return childIndex == rowEnd;
2004            case View.FOCUS_UP:
2005                // coming from bottom, need to be in last row
2006                return rowEnd == count - 1;
2007            case View.FOCUS_FORWARD:
2008                // coming from top-left, need to be first in top row
2009                return childIndex == rowStart && rowStart == 0;
2010            case View.FOCUS_BACKWARD:
2011                // coming from bottom-right, need to be last in bottom row
2012                return childIndex == rowEnd && rowEnd == count - 1;
2013            default:
2014                throw new IllegalArgumentException("direction must be one of "
2015                        + "{FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, FOCUS_RIGHT, "
2016                        + "FOCUS_FORWARD, FOCUS_BACKWARD}.");
2017        }
2018    }
2019
2020    /**
2021     * Set the gravity for this grid. Gravity describes how the child views
2022     * are horizontally aligned. Defaults to Gravity.LEFT
2023     *
2024     * @param gravity the gravity to apply to this grid's children
2025     *
2026     * @attr ref android.R.styleable#GridView_gravity
2027     */
2028    public void setGravity(int gravity) {
2029        if (mGravity != gravity) {
2030            mGravity = gravity;
2031            requestLayoutIfNecessary();
2032        }
2033    }
2034
2035    /**
2036     * Describes how the child views are horizontally aligned. Defaults to Gravity.LEFT
2037     *
2038     * @return the gravity that will be applied to this grid's children
2039     *
2040     * @attr ref android.R.styleable#GridView_gravity
2041     */
2042    public int getGravity() {
2043        return mGravity;
2044    }
2045
2046    /**
2047     * Set the amount of horizontal (x) spacing to place between each item
2048     * in the grid.
2049     *
2050     * @param horizontalSpacing The amount of horizontal space between items,
2051     * in pixels.
2052     *
2053     * @attr ref android.R.styleable#GridView_horizontalSpacing
2054     */
2055    public void setHorizontalSpacing(int horizontalSpacing) {
2056        if (horizontalSpacing != mRequestedHorizontalSpacing) {
2057            mRequestedHorizontalSpacing = horizontalSpacing;
2058            requestLayoutIfNecessary();
2059        }
2060    }
2061
2062    /**
2063     * Returns the amount of horizontal spacing currently used between each item in the grid.
2064     *
2065     * <p>This is only accurate for the current layout. If {@link #setHorizontalSpacing(int)}
2066     * has been called but layout is not yet complete, this method may return a stale value.
2067     * To get the horizontal spacing that was explicitly requested use
2068     * {@link #getRequestedHorizontalSpacing()}.</p>
2069     *
2070     * @return Current horizontal spacing between each item in pixels
2071     *
2072     * @see #setHorizontalSpacing(int)
2073     * @see #getRequestedHorizontalSpacing()
2074     *
2075     * @attr ref android.R.styleable#GridView_horizontalSpacing
2076     */
2077    public int getHorizontalSpacing() {
2078        return mHorizontalSpacing;
2079    }
2080
2081    /**
2082     * Returns the requested amount of horizontal spacing between each item in the grid.
2083     *
2084     * <p>The value returned may have been supplied during inflation as part of a style,
2085     * the default GridView style, or by a call to {@link #setHorizontalSpacing(int)}.
2086     * If layout is not yet complete or if GridView calculated a different horizontal spacing
2087     * from what was requested, this may return a different value from
2088     * {@link #getHorizontalSpacing()}.</p>
2089     *
2090     * @return The currently requested horizontal spacing between items, in pixels
2091     *
2092     * @see #setHorizontalSpacing(int)
2093     * @see #getHorizontalSpacing()
2094     *
2095     * @attr ref android.R.styleable#GridView_horizontalSpacing
2096     */
2097    public int getRequestedHorizontalSpacing() {
2098        return mRequestedHorizontalSpacing;
2099    }
2100
2101    /**
2102     * Set the amount of vertical (y) spacing to place between each item
2103     * in the grid.
2104     *
2105     * @param verticalSpacing The amount of vertical space between items,
2106     * in pixels.
2107     *
2108     * @see #getVerticalSpacing()
2109     *
2110     * @attr ref android.R.styleable#GridView_verticalSpacing
2111     */
2112    public void setVerticalSpacing(int verticalSpacing) {
2113        if (verticalSpacing != mVerticalSpacing) {
2114            mVerticalSpacing = verticalSpacing;
2115            requestLayoutIfNecessary();
2116        }
2117    }
2118
2119    /**
2120     * Returns the amount of vertical spacing between each item in the grid.
2121     *
2122     * @return The vertical spacing between items in pixels
2123     *
2124     * @see #setVerticalSpacing(int)
2125     *
2126     * @attr ref android.R.styleable#GridView_verticalSpacing
2127     */
2128    public int getVerticalSpacing() {
2129        return mVerticalSpacing;
2130    }
2131
2132    /**
2133     * Control how items are stretched to fill their space.
2134     *
2135     * @param stretchMode Either {@link #NO_STRETCH},
2136     * {@link #STRETCH_SPACING}, {@link #STRETCH_SPACING_UNIFORM}, or {@link #STRETCH_COLUMN_WIDTH}.
2137     *
2138     * @attr ref android.R.styleable#GridView_stretchMode
2139     */
2140    public void setStretchMode(@StretchMode int stretchMode) {
2141        if (stretchMode != mStretchMode) {
2142            mStretchMode = stretchMode;
2143            requestLayoutIfNecessary();
2144        }
2145    }
2146
2147    @StretchMode
2148    public int getStretchMode() {
2149        return mStretchMode;
2150    }
2151
2152    /**
2153     * Set the width of columns in the grid.
2154     *
2155     * @param columnWidth The column width, in pixels.
2156     *
2157     * @attr ref android.R.styleable#GridView_columnWidth
2158     */
2159    public void setColumnWidth(int columnWidth) {
2160        if (columnWidth != mRequestedColumnWidth) {
2161            mRequestedColumnWidth = columnWidth;
2162            requestLayoutIfNecessary();
2163        }
2164    }
2165
2166    /**
2167     * Return the width of a column in the grid.
2168     *
2169     * <p>This may not be valid yet if a layout is pending.</p>
2170     *
2171     * @return The column width in pixels
2172     *
2173     * @see #setColumnWidth(int)
2174     * @see #getRequestedColumnWidth()
2175     *
2176     * @attr ref android.R.styleable#GridView_columnWidth
2177     */
2178    public int getColumnWidth() {
2179        return mColumnWidth;
2180    }
2181
2182    /**
2183     * Return the requested width of a column in the grid.
2184     *
2185     * <p>This may not be the actual column width used. Use {@link #getColumnWidth()}
2186     * to retrieve the current real width of a column.</p>
2187     *
2188     * @return The requested column width in pixels
2189     *
2190     * @see #setColumnWidth(int)
2191     * @see #getColumnWidth()
2192     *
2193     * @attr ref android.R.styleable#GridView_columnWidth
2194     */
2195    public int getRequestedColumnWidth() {
2196        return mRequestedColumnWidth;
2197    }
2198
2199    /**
2200     * Set the number of columns in the grid
2201     *
2202     * @param numColumns The desired number of columns.
2203     *
2204     * @attr ref android.R.styleable#GridView_numColumns
2205     */
2206    public void setNumColumns(int numColumns) {
2207        if (numColumns != mRequestedNumColumns) {
2208            mRequestedNumColumns = numColumns;
2209            requestLayoutIfNecessary();
2210        }
2211    }
2212
2213    /**
2214     * Get the number of columns in the grid.
2215     * Returns {@link #AUTO_FIT} if the Grid has never been laid out.
2216     *
2217     * @attr ref android.R.styleable#GridView_numColumns
2218     *
2219     * @see #setNumColumns(int)
2220     */
2221    @ViewDebug.ExportedProperty
2222    public int getNumColumns() {
2223        return mNumColumns;
2224    }
2225
2226    /**
2227     * Make sure views are touching the top or bottom edge, as appropriate for
2228     * our gravity
2229     */
2230    private void adjustViewsUpOrDown() {
2231        final int childCount = getChildCount();
2232
2233        if (childCount > 0) {
2234            int delta;
2235            View child;
2236
2237            if (!mStackFromBottom) {
2238                // Uh-oh -- we came up short. Slide all views up to make them
2239                // align with the top
2240                child = getChildAt(0);
2241                delta = child.getTop() - mListPadding.top;
2242                if (mFirstPosition != 0) {
2243                    // It's OK to have some space above the first item if it is
2244                    // part of the vertical spacing
2245                    delta -= mVerticalSpacing;
2246                }
2247                if (delta < 0) {
2248                    // We only are looking to see if we are too low, not too high
2249                    delta = 0;
2250                }
2251            } else {
2252                // we are too high, slide all views down to align with bottom
2253                child = getChildAt(childCount - 1);
2254                delta = child.getBottom() - (getHeight() - mListPadding.bottom);
2255
2256                if (mFirstPosition + childCount < mItemCount) {
2257                    // It's OK to have some space below the last item if it is
2258                    // part of the vertical spacing
2259                    delta += mVerticalSpacing;
2260                }
2261
2262                if (delta > 0) {
2263                    // We only are looking to see if we are too high, not too low
2264                    delta = 0;
2265                }
2266            }
2267
2268            if (delta != 0) {
2269                offsetChildrenTopAndBottom(-delta);
2270            }
2271        }
2272    }
2273
2274    @Override
2275    protected int computeVerticalScrollExtent() {
2276        final int count = getChildCount();
2277        if (count > 0) {
2278            final int numColumns = mNumColumns;
2279            final int rowCount = (count + numColumns - 1) / numColumns;
2280
2281            int extent = rowCount * 100;
2282
2283            View view = getChildAt(0);
2284            final int top = view.getTop();
2285            int height = view.getHeight();
2286            if (height > 0) {
2287                extent += (top * 100) / height;
2288            }
2289
2290            view = getChildAt(count - 1);
2291            final int bottom = view.getBottom();
2292            height = view.getHeight();
2293            if (height > 0) {
2294                extent -= ((bottom - getHeight()) * 100) / height;
2295            }
2296
2297            return extent;
2298        }
2299        return 0;
2300    }
2301
2302    @Override
2303    protected int computeVerticalScrollOffset() {
2304        if (mFirstPosition >= 0 && getChildCount() > 0) {
2305            final View view = getChildAt(0);
2306            final int top = view.getTop();
2307            int height = view.getHeight();
2308            if (height > 0) {
2309                final int numColumns = mNumColumns;
2310                final int rowCount = (mItemCount + numColumns - 1) / numColumns;
2311                // In case of stackFromBottom the calculation of whichRow needs
2312                // to take into account that counting from the top the first row
2313                // might not be entirely filled.
2314                final int oddItemsOnFirstRow = isStackFromBottom() ? ((rowCount * numColumns) -
2315                        mItemCount) : 0;
2316                final int whichRow = (mFirstPosition + oddItemsOnFirstRow) / numColumns;
2317                return Math.max(whichRow * 100 - (top * 100) / height +
2318                        (int) ((float) mScrollY / getHeight() * rowCount * 100), 0);
2319            }
2320        }
2321        return 0;
2322    }
2323
2324    @Override
2325    protected int computeVerticalScrollRange() {
2326        // TODO: Account for vertical spacing too
2327        final int numColumns = mNumColumns;
2328        final int rowCount = (mItemCount + numColumns - 1) / numColumns;
2329        int result = Math.max(rowCount * 100, 0);
2330        if (mScrollY != 0) {
2331            // Compensate for overscroll
2332            result += Math.abs((int) ((float) mScrollY / getHeight() * rowCount * 100));
2333        }
2334        return result;
2335    }
2336
2337    @Override
2338    public CharSequence getAccessibilityClassName() {
2339        return GridView.class.getName();
2340    }
2341
2342    /** @hide */
2343    @Override
2344    public void onInitializeAccessibilityNodeInfoInternal(AccessibilityNodeInfo info) {
2345        super.onInitializeAccessibilityNodeInfoInternal(info);
2346
2347        final int columnsCount = getNumColumns();
2348        final int rowsCount = getCount() / columnsCount;
2349        final int selectionMode = getSelectionModeForAccessibility();
2350        final CollectionInfo collectionInfo = CollectionInfo.obtain(
2351                rowsCount, columnsCount, false, selectionMode);
2352        info.setCollectionInfo(collectionInfo);
2353
2354        if (columnsCount > 0 || rowsCount > 0) {
2355            info.addAction(AccessibilityAction.ACTION_SCROLL_TO_POSITION);
2356        }
2357    }
2358
2359    /** @hide */
2360    @Override
2361    public boolean performAccessibilityActionInternal(int action, Bundle arguments) {
2362        if (super.performAccessibilityActionInternal(action, arguments)) {
2363            return true;
2364        }
2365
2366        switch (action) {
2367            case R.id.accessibilityActionScrollToPosition: {
2368                // GridView only supports scrolling in one direction, so we can
2369                // ignore the column argument.
2370                final int numColumns = getNumColumns();
2371                final int row = arguments.getInt(AccessibilityNodeInfo.ACTION_ARGUMENT_ROW_INT, -1);
2372                final int position = Math.min(row * numColumns, getCount() - 1);
2373                if (row >= 0) {
2374                    // The accessibility service gets data asynchronously, so
2375                    // we'll be a little lenient by clamping the last position.
2376                    smoothScrollToPosition(position);
2377                    return true;
2378                }
2379            } break;
2380        }
2381
2382        return false;
2383    }
2384
2385    @Override
2386    public void onInitializeAccessibilityNodeInfoForItem(
2387            View view, int position, AccessibilityNodeInfo info) {
2388        super.onInitializeAccessibilityNodeInfoForItem(view, position, info);
2389
2390        final int count = getCount();
2391        final int columnsCount = getNumColumns();
2392        final int rowsCount = count / columnsCount;
2393
2394        final int row;
2395        final int column;
2396        if (!mStackFromBottom) {
2397            column = position % columnsCount;
2398            row = position / columnsCount;
2399        } else {
2400            final int invertedIndex = count - 1 - position;
2401
2402            column = columnsCount - 1 - (invertedIndex % columnsCount);
2403            row = rowsCount - 1 - invertedIndex / columnsCount;
2404        }
2405
2406        final LayoutParams lp = (LayoutParams) view.getLayoutParams();
2407        final boolean isHeading = lp != null && lp.viewType == ITEM_VIEW_TYPE_HEADER_OR_FOOTER;
2408        final boolean isSelected = isItemChecked(position);
2409        final CollectionItemInfo itemInfo = CollectionItemInfo.obtain(
2410                row, 1, column, 1, isHeading, isSelected);
2411        info.setCollectionItemInfo(itemInfo);
2412    }
2413
2414    /** @hide */
2415    @Override
2416    protected void encodeProperties(@NonNull ViewHierarchyEncoder encoder) {
2417        super.encodeProperties(encoder);
2418        encoder.addProperty("numColumns", getNumColumns());
2419    }
2420}
2421