RecyclerViewActivity.java revision 63c8ab9435d707a23e2045af3be410ea7deed895 
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.os.Bundle;
24import android.support.v4.view.MenuItemCompat;
25import android.support.v7.widget.RecyclerView;
26import android.util.DisplayMetrics;
27import android.util.TypedValue;
28import android.view.Menu;
29import android.view.MenuItem;
30import android.view.View;
31import android.view.ViewGroup;
32import android.view.View.MeasureSpec;
33import android.widget.TextView;
34import com.example.android.supportv7.Cheeses;
35
36import java.util.ArrayList;
37import java.util.Collections;
38
39public class RecyclerViewActivity extends Activity {
40    private RecyclerView mRecyclerView;
41
42    @Override
43    protected void onCreate(Bundle savedInstanceState) {
44        super.onCreate(savedInstanceState);
45
46        final RecyclerView rv = new RecyclerView(this);
47        rv.setLayoutManager(new MyLayoutManager(this));
48        rv.setHasFixedSize(true);
49        rv.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
50                ViewGroup.LayoutParams.MATCH_PARENT));
51        rv.setAdapter(new MyAdapter(Cheeses.sCheeseStrings));
52        setContentView(rv);
53
54        mRecyclerView = rv;
55    }
56
57    @Override
58    public boolean onCreateOptionsMenu(Menu menu) {
59        super.onCreateOptionsMenu(menu);
60        MenuItemCompat.setShowAsAction(menu.add("Layout"), MenuItemCompat.SHOW_AS_ACTION_IF_ROOM);
61        return true;
62    }
63
64    @Override
65    public boolean onOptionsItemSelected(MenuItem item) {
66        mRecyclerView.requestLayout();
67        return super.onOptionsItemSelected(item);
68    }
69
70    private static final int SCROLL_DISTANCE = 80; // dp
71
72    /**
73     * A basic ListView-style LayoutManager.
74     */
75    class MyLayoutManager extends RecyclerView.LayoutManager {
76        private static final String TAG = "MyLayoutManager";
77        private int mFirstPosition;
78        private final int mScrollDistance;
79
80        public MyLayoutManager(Context c) {
81            final DisplayMetrics dm = c.getResources().getDisplayMetrics();
82            mScrollDistance = (int) (SCROLL_DISTANCE * dm.density + 0.5f);
83        }
84
85        @Override
86        public void layoutChildren(RecyclerView.Adapter adapter, RecyclerView.Recycler recycler) {
87            final int parentBottom = getHeight() - getPaddingBottom();
88
89            final View oldTopView = getChildCount() > 0 ? getChildAt(0) : null;
90            int oldTop = getPaddingTop();
91            if (oldTopView != null) {
92                oldTop = oldTopView.getTop();
93            }
94
95            detachAndScrapAttachedViews(recycler);
96
97            int top = oldTop;
98            int bottom;
99            final int left = getPaddingLeft();
100            final int right = getWidth() - getPaddingRight();
101
102            final int count = adapter.getItemCount();
103            for (int i = 0; mFirstPosition + i < count && top < parentBottom; i++, top = bottom) {
104                View v = recycler.getViewForPosition(adapter, mFirstPosition + i);
105                addView(v, i);
106                measureChildWithMargins(v, 0, 0);
107                bottom = top + v.getMeasuredHeight();
108                v.layout(left, top, right, bottom);
109            }
110
111            removeAndRecycleScrap(recycler);
112        }
113
114        @Override
115        public RecyclerView.LayoutParams generateDefaultLayoutParams() {
116            return new RecyclerView.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
117                    ViewGroup.LayoutParams.WRAP_CONTENT);
118        }
119
120        @Override
121        public boolean canScrollVertically() {
122            return true;
123        }
124
125        @Override
126        public int scrollVerticallyBy(int dy, RecyclerView.Adapter adapter,
127                RecyclerView.Recycler recycler) {
128            if (getChildCount() == 0) {
129                return 0;
130            }
131
132            int scrolled = 0;
133            final int left = getPaddingLeft();
134            final int right = getWidth() - getPaddingRight();
135            if (dy < 0) {
136                while (scrolled > dy) {
137                    final View topView = getChildAt(0);
138                    final int hangingTop = Math.max(-topView.getTop(), 0);
139                    final int scrollBy = Math.min(scrolled - dy, hangingTop);
140                    scrolled -= scrollBy;
141                    offsetChildrenVertical(scrollBy);
142                    if (mFirstPosition > 0 && scrolled > dy) {
143                        mFirstPosition--;
144                        View v = recycler.getViewForPosition(adapter, mFirstPosition);
145                        addView(v, 0);
146                        measureChildWithMargins(v, 0, 0);
147                        final int bottom = topView.getTop(); // TODO decorated top?
148                        final int top = bottom - v.getMeasuredHeight();
149                        v.layout(left, top, right, bottom);
150                    } else {
151                        break;
152                    }
153                }
154            } else if (dy > 0) {
155                final int parentHeight = getHeight();
156                while (scrolled < dy) {
157                    final View bottomView = getChildAt(getChildCount() - 1);
158                    final int hangingBottom = Math.max(bottomView.getBottom() - parentHeight, 0);
159                    final int scrollBy = -Math.min(dy - scrolled, hangingBottom);
160                    scrolled -= scrollBy;
161                    offsetChildrenVertical(scrollBy);
162                    if (scrolled < dy && getItemCount() > mFirstPosition + getChildCount()) {
163                        View v = recycler.getViewForPosition(adapter,
164                                mFirstPosition + getChildCount());
165                        final int top = getChildAt(getChildCount() - 1).getBottom();
166                        addView(v);
167                        measureChildWithMargins(v, 0, 0);
168                        final int bottom = top + v.getMeasuredHeight();
169                        v.layout(left, top, right, bottom);
170                    } else {
171                        break;
172                    }
173                }
174            }
175            recycleViewsOutOfBounds(recycler);
176            return scrolled;
177        }
178
179        @Override
180        public View onFocusSearchFailed(View focused, int direction,
181                RecyclerView.Adapter adapter, RecyclerView.Recycler recycler) {
182            final int oldCount = getChildCount();
183
184            if (oldCount == 0) {
185                return null;
186            }
187
188            final int left = getPaddingLeft();
189            final int right = getWidth() - getPaddingRight();
190
191            View toFocus = null;
192            int newViewsHeight = 0;
193            if (direction == View.FOCUS_UP || direction == View.FOCUS_BACKWARD) {
194                while (mFirstPosition > 0 && newViewsHeight < mScrollDistance) {
195                    mFirstPosition--;
196                    View v = recycler.getViewForPosition(adapter, mFirstPosition);
197                    final int bottom = getChildAt(0).getTop(); // TODO decorated top?
198                    addView(v, 0);
199                    measureChildWithMargins(v, 0, 0);
200                    final int top = bottom - v.getMeasuredHeight();
201                    v.layout(left, top, right, bottom);
202                    if (v.isFocusable()) {
203                        toFocus = v;
204                        break;
205                    }
206                }
207            }
208            if (direction == View.FOCUS_DOWN || direction == View.FOCUS_FORWARD) {
209                while (mFirstPosition + getChildCount() < getItemCount() &&
210                        newViewsHeight < mScrollDistance) {
211                    View v = recycler.getViewForPosition(adapter, mFirstPosition + getChildCount());
212                    final int top = getChildAt(getChildCount() - 1).getBottom();
213                    addView(v);
214                    measureChildWithMargins(v, 0, 0);
215                    final int bottom = top + v.getMeasuredHeight();
216                    v.layout(left, top, right, bottom);
217                    if (v.isFocusable()) {
218                        toFocus = v;
219                        break;
220                    }
221                }
222            }
223
224            return toFocus;
225        }
226
227        public void recycleViewsOutOfBounds(RecyclerView.Recycler recycler) {
228            final int childCount = getChildCount();
229            final int parentWidth = getWidth();
230            final int parentHeight = getHeight();
231            boolean foundFirst = false;
232            int first = 0;
233            int last = 0;
234            for (int i = 0; i < childCount; i++) {
235                final View v = getChildAt(i);
236                if (v.hasFocus() || (v.getRight() >= 0 && v.getLeft() <= parentWidth &&
237                        v.getBottom() >= 0 && v.getTop() <= parentHeight)) {
238                    if (!foundFirst) {
239                        first = i;
240                        foundFirst = true;
241                    }
242                    last = i;
243                }
244            }
245            for (int i = childCount - 1; i > last; i--) {
246                removeAndRecycleViewAt(i, recycler);
247            }
248            for (int i = first - 1; i >= 0; i--) {
249                removeAndRecycleViewAt(i, recycler);
250            }
251            if (getChildCount() == 0) {
252                mFirstPosition = 0;
253            } else {
254                mFirstPosition += first;
255            }
256        }
257    }
258
259    class MyAdapter extends RecyclerView.Adapter<ViewHolder> {
260        private int mBackground;
261        private ArrayList<String> mValues;
262
263        public MyAdapter(String[] strings) {
264            TypedValue val = new TypedValue();
265            RecyclerViewActivity.this.getTheme().resolveAttribute(
266                    R.attr.selectableItemBackground, val, true);
267            mBackground = val.resourceId;
268            mValues = new ArrayList<String>();
269            Collections.addAll(mValues, strings);
270        }
271
272        @Override
273        public ViewHolder createViewHolder(ViewGroup parent, int viewType) {
274            final ViewHolder h = new ViewHolder(new TextView(RecyclerViewActivity.this));
275            h.textView.setMinimumHeight(128);
276            h.textView.setFocusable(true);
277            h.textView.setBackgroundResource(mBackground);
278            h.textView.setOnClickListener(new View.OnClickListener() {
279                @Override
280                public void onClick(View v) {
281                    final int pos = h.getPosition();
282                    if (mValues.size() > pos + 1) {
283                        final String t = mValues.get(pos);
284                        mValues.set(pos, mValues.get(pos + 1));
285                        mValues.set(pos + 1, t);
286                        notifyItemRangeChanged(pos, 2);
287                    }
288                }
289            });
290            return h;
291        }
292
293        @Override
294        public void bindViewHolder(ViewHolder holder, int position) {
295            holder.textView.setText(mValues.get(position));
296        }
297
298        @Override
299        public int getItemCount() {
300            return mValues.size();
301        }
302    }
303
304    static class ViewHolder extends RecyclerView.ViewHolder {
305        public TextView textView;
306
307        public ViewHolder(TextView v) {
308            super(v);
309            textView = v;
310        }
311    }
312}
313