RecyclerViewActivity.java revision 90e0922d7d57ad748b919dfe21c63f03987227e7 
1/*
2 * Copyright (C) 2013 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
17
18package com.example.android.supportv7.widget;
19
20import android.R;
21import android.app.Activity;
22import android.content.Context;
23import android.graphics.Rect;
24import android.os.Bundle;
25import android.support.v4.view.MenuItemCompat;
26import android.support.v7.widget.RecyclerView;
27import android.util.DisplayMetrics;
28import android.util.TypedValue;
29import android.view.Menu;
30import android.view.MenuItem;
31import android.view.View;
32import android.view.ViewGroup;
33import android.view.View.MeasureSpec;
34import android.widget.TextView;
35import com.example.android.supportv7.Cheeses;
36
37import java.util.ArrayList;
38import java.util.Collections;
39
40public class RecyclerViewActivity extends Activity {
41    private RecyclerView mRecyclerView;
42
43    @Override
44    protected void onCreate(Bundle savedInstanceState) {
45        super.onCreate(savedInstanceState);
46
47        final RecyclerView rv = new RecyclerView(this);
48        rv.setLayoutManager(new MyLayoutManager(this));
49        rv.setHasFixedSize(true);
50        rv.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
51                ViewGroup.LayoutParams.MATCH_PARENT));
52        rv.setAdapter(new MyAdapter(Cheeses.sCheeseStrings));
53        setContentView(rv);
54
55        mRecyclerView = rv;
56    }
57
58    @Override
59    public boolean onCreateOptionsMenu(Menu menu) {
60        super.onCreateOptionsMenu(menu);
61        MenuItemCompat.setShowAsAction(menu.add("Layout"), MenuItemCompat.SHOW_AS_ACTION_IF_ROOM);
62        return true;
63    }
64
65    @Override
66    public boolean onOptionsItemSelected(MenuItem item) {
67        mRecyclerView.requestLayout();
68        return super.onOptionsItemSelected(item);
69    }
70
71    private static final int SCROLL_DISTANCE = 80; // dp
72
73    /**
74     * A basic ListView-style LayoutManager.
75     */
76    class MyLayoutManager extends RecyclerView.LayoutManager {
77        private static final String TAG = "MyLayoutManager";
78        private int mFirstPosition;
79        private final int mScrollDistance;
80
81        public MyLayoutManager(Context c) {
82            final DisplayMetrics dm = c.getResources().getDisplayMetrics();
83            mScrollDistance = (int) (SCROLL_DISTANCE * dm.density + 0.5f);
84        }
85
86        @Override
87        public void layoutChildren(RecyclerView.Adapter adapter, RecyclerView.Recycler recycler) {
88            final int parentBottom = getHeight() - getPaddingBottom();
89
90            final View oldTopView = getChildCount() > 0 ? getChildAt(0) : null;
91            int oldTop = getPaddingTop();
92            if (oldTopView != null) {
93                oldTop = oldTopView.getTop();
94            }
95
96            recycler.scrapAllViewsAttached();
97
98            int top = oldTop;
99            int bottom;
100            final int left = getPaddingLeft();
101            final int right = getWidth() - getPaddingRight();
102
103            final int count = adapter.getItemCount();
104            for (int i = 0; mFirstPosition + i < count && top < parentBottom; i++, top = bottom) {
105                View v = recycler.getViewForPosition(adapter, mFirstPosition + i);
106                addView(v, i);
107                v.measure(MeasureSpec.makeMeasureSpec(right - left, MeasureSpec.EXACTLY),
108                        MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
109                bottom = top + v.getMeasuredHeight();
110                v.layout(left, top, right, bottom);
111            }
112
113            recycler.detachDirtyScrapViews();
114        }
115
116        @Override
117        public RecyclerView.LayoutParams generateDefaultLayoutParams() {
118            return new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
119                    ViewGroup.LayoutParams.WRAP_CONTENT);
120        }
121
122        @Override
123        public boolean canScrollVertically() {
124            return true;
125        }
126
127        @Override
128        public int scrollVerticallyBy(int dy, RecyclerView.Adapter adapter,
129                RecyclerView.Recycler recycler) {
130            if (getChildCount() == 0) {
131                return 0;
132            }
133
134            int scrolled = 0;
135            final int left = getPaddingLeft();
136            final int right = getWidth() - getPaddingRight();
137            if (dy < 0) {
138                while (scrolled > dy) {
139                    final View topView = getChildAt(0);
140                    final int hangingTop = Math.max(-topView.getTop(), 0);
141                    final int scrollBy = Math.min(scrolled - dy, hangingTop);
142                    scrolled -= scrollBy;
143                    offsetChildrenVertical(scrollBy);
144                    if (mFirstPosition > 0 && scrolled > dy) {
145                        mFirstPosition--;
146                        View v = recycler.getViewForPosition(adapter, mFirstPosition);
147                        addView(v, 0);
148                        v.measure(MeasureSpec.makeMeasureSpec(right - left, MeasureSpec.EXACTLY),
149                                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
150                        final int bottom = topView.getTop(); // TODO decorated top?
151                        final int top = bottom - v.getMeasuredHeight();
152                        v.layout(left, top, right, bottom);
153                    } else {
154                        break;
155                    }
156                }
157            } else if (dy > 0) {
158                final int parentHeight = getHeight();
159                while (scrolled < dy) {
160                    final View bottomView = getChildAt(getChildCount() - 1);
161                    final int hangingBottom = Math.max(bottomView.getBottom() - parentHeight, 0);
162                    final int scrollBy = -Math.min(dy - scrolled, hangingBottom);
163                    scrolled -= scrollBy;
164                    offsetChildrenVertical(scrollBy);
165                    if (scrolled < dy && getItemCount() > mFirstPosition + getChildCount()) {
166                        View v = recycler.getViewForPosition(adapter,
167                                mFirstPosition + getChildCount());
168                        final int top = getChildAt(getChildCount() - 1).getBottom();
169                        addView(v);
170                        v.measure(MeasureSpec.makeMeasureSpec(right - left, MeasureSpec.EXACTLY),
171                                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
172                        final int bottom = top + v.getMeasuredHeight();
173                        v.layout(left, top, right, bottom);
174                    } else {
175                        break;
176                    }
177                }
178            }
179            detachAndScrapViewsOutOfBounds(recycler);
180            return scrolled;
181        }
182
183        @Override
184        public View onFocusSearchFailed(View focused, int direction,
185                RecyclerView.Adapter adapter, RecyclerView.Recycler recycler) {
186            final int oldCount = getChildCount();
187
188            if (oldCount == 0) {
189                return null;
190            }
191
192            final int left = getPaddingLeft();
193            final int right = getWidth() - getPaddingRight();
194
195            View toFocus = null;
196            int newViewsHeight = 0;
197            if (direction == View.FOCUS_UP || direction == View.FOCUS_BACKWARD) {
198                while (mFirstPosition > 0 && newViewsHeight < mScrollDistance) {
199                    mFirstPosition--;
200                    View v = recycler.getViewForPosition(adapter, mFirstPosition);
201                    final int bottom = getChildAt(0).getTop(); // TODO decorated top?
202                    addView(v, 0);
203                    v.measure(MeasureSpec.makeMeasureSpec(right - left, MeasureSpec.EXACTLY),
204                            MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
205                    final int top = bottom - v.getMeasuredHeight();
206                    v.layout(left, top, right, bottom);
207                    if (v.isFocusable()) {
208                        toFocus = v;
209                        break;
210                    }
211                }
212            }
213            if (direction == View.FOCUS_DOWN || direction == View.FOCUS_FORWARD) {
214                while (mFirstPosition + getChildCount() < getItemCount() &&
215                        newViewsHeight < mScrollDistance) {
216                    View v = recycler.getViewForPosition(adapter, mFirstPosition + getChildCount());
217                    final int top = getChildAt(getChildCount() - 1).getBottom();
218                    addView(v);
219                    v.measure(MeasureSpec.makeMeasureSpec(right - left, MeasureSpec.EXACTLY),
220                            MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
221                    final int bottom = top + v.getMeasuredHeight();
222                    v.layout(left, top, right, bottom);
223                    if (v.isFocusable()) {
224                        toFocus = v;
225                        break;
226                    }
227                }
228            }
229
230            return toFocus;
231        }
232
233        public void detachAndScrapViewsOutOfBounds(RecyclerView.Recycler recycler) {
234            final int childCount = getChildCount();
235            final int parentWidth = getWidth();
236            final int parentHeight = getHeight();
237            boolean foundFirst = false;
238            int first = 0;
239            int last = 0;
240            for (int i = 0; i < childCount; i++) {
241                final View v = getChildAt(i);
242                if (v.hasFocus() || (v.getRight() >= 0 && v.getLeft() <= parentWidth &&
243                        v.getBottom() >= 0 && v.getTop() <= parentHeight)) {
244                    if (!foundFirst) {
245                        first = i;
246                        foundFirst = true;
247                    }
248                    last = i;
249                }
250            }
251            for (int i = childCount - 1; i > last; i--) {
252                recycler.detachAndScrapView(getChildAt(i));
253            }
254            for (int i = first - 1; i >= 0; i--) {
255                recycler.detachAndScrapView(getChildAt(i));
256            }
257            if (getChildCount() == 0) {
258                mFirstPosition = 0;
259            } else {
260                mFirstPosition += first;
261            }
262        }
263    }
264
265    class MyAdapter extends RecyclerView.Adapter {
266        private int mBackground;
267        private ArrayList<String> mValues;
268
269        public MyAdapter(String[] strings) {
270            TypedValue val = new TypedValue();
271            RecyclerViewActivity.this.getTheme().resolveAttribute(
272                    R.attr.selectableItemBackground, val, true);
273            mBackground = val.resourceId;
274            mValues = new ArrayList<String>();
275            Collections.addAll(mValues, strings);
276        }
277
278        @Override
279        public RecyclerView.ViewHolder createViewHolder(ViewGroup parent, int viewType) {
280            final ViewHolder h = new ViewHolder(new TextView(RecyclerViewActivity.this));
281            h.textView.setMinimumHeight(128);
282            h.textView.setFocusable(true);
283            h.textView.setBackgroundResource(mBackground);
284            h.textView.setOnClickListener(new View.OnClickListener() {
285                @Override
286                public void onClick(View v) {
287                    final int pos = h.getPosition();
288                    if (mValues.size() > pos + 1) {
289                        final String t = mValues.get(pos);
290                        mValues.set(pos, mValues.get(pos + 1));
291                        mValues.set(pos + 1, t);
292                        notifyDataSetChanged();
293                    }
294                }
295            });
296            return h;
297        }
298
299        @Override
300        public void bindViewHolder(RecyclerView.ViewHolder holder, int position) {
301            ((ViewHolder) holder).textView.setText(mValues.get(position));
302        }
303
304        @Override
305        public int getItemCount() {
306            return mValues.size();
307        }
308    }
309
310    static class ViewHolder extends RecyclerView.ViewHolder {
311        public TextView textView;
312
313        public ViewHolder(TextView v) {
314            super(v);
315            textView = v;
316        }
317    }
318}
319