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      1 /*
      2  * Copyright (C) 2017 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 package com.example.android.leanback;
     18 
     19 import android.graphics.Bitmap;
     20 import android.os.AsyncTask;
     21 import android.support.v17.leanback.widget.PlaybackSeekDataProvider;
     22 import android.support.v4.util.LruCache;
     23 import android.util.Log;
     24 import android.util.SparseArray;
     25 
     26 import java.util.Iterator;
     27 import java.util.Map;
     28 
     29 /**
     30  *
     31  * Base class that implements PlaybackSeekDataProvider using AsyncTask.THREAD_POOL_EXECUTOR with
     32  * prefetching.
     33  */
     34 public abstract class PlaybackSeekAsyncDataProvider extends PlaybackSeekDataProvider {
     35 
     36     static final String TAG = "SeekAsyncProvider";
     37 
     38     long[] mSeekPositions;
     39     // mCache is for the bitmap requested by user
     40     final LruCache<Integer, Bitmap> mCache;
     41     // mPrefetchCache is for the bitmap not requested by user but prefetched by heuristic
     42     // estimation. We use a different LruCache so that items in mCache will not be evicted by
     43     // prefeteched items.
     44     final LruCache<Integer, Bitmap> mPrefetchCache;
     45     final SparseArray<LoadBitmapTask> mRequests = new SparseArray<>();
     46     int mLastRequestedIndex = -1;
     47 
     48     protected boolean isCancelled(Object task) {
     49         return ((AsyncTask) task).isCancelled();
     50     }
     51 
     52     protected abstract Bitmap doInBackground(Object task, int index, long position);
     53 
     54     class LoadBitmapTask extends AsyncTask<Object, Object, Bitmap> {
     55 
     56         int mIndex;
     57         ResultCallback mResultCallback;
     58 
     59         LoadBitmapTask(int index, ResultCallback callback) {
     60             mIndex = index;
     61             mResultCallback = callback;
     62         }
     63 
     64         @Override
     65         protected Bitmap doInBackground(Object[] params) {
     66             return PlaybackSeekAsyncDataProvider.this
     67                     .doInBackground(this, mIndex, mSeekPositions[mIndex]);
     68         }
     69 
     70         @Override
     71         protected void onPostExecute(Bitmap bitmap) {
     72             mRequests.remove(mIndex);
     73             Log.d(TAG, "thumb Loaded " + mIndex);
     74             if (mResultCallback != null) {
     75                 mCache.put(mIndex, bitmap);
     76                 mResultCallback.onThumbnailLoaded(bitmap, mIndex);
     77             } else {
     78                 mPrefetchCache.put(mIndex, bitmap);
     79             }
     80         }
     81 
     82     }
     83 
     84     public PlaybackSeekAsyncDataProvider() {
     85         this(16, 24);
     86     }
     87 
     88     public PlaybackSeekAsyncDataProvider(int cacheSize, int prefetchCacheSize) {
     89         mCache = new LruCache<Integer, Bitmap>(cacheSize);
     90         mPrefetchCache = new LruCache<Integer, Bitmap>(prefetchCacheSize);
     91     }
     92 
     93     public void setSeekPositions(long[] positions) {
     94         mSeekPositions = positions;
     95     }
     96 
     97     @Override
     98     public long[] getSeekPositions() {
     99         return mSeekPositions;
    100     }
    101 
    102     @Override
    103     public void getThumbnail(int index, ResultCallback callback) {
    104         Integer key = index;
    105         Bitmap bitmap = mCache.get(key);
    106         if (bitmap != null) {
    107             callback.onThumbnailLoaded(bitmap, index);
    108         } else {
    109             bitmap = mPrefetchCache.get(key);
    110             if (bitmap != null) {
    111                 mCache.put(key, bitmap);
    112                 mPrefetchCache.remove(key);
    113                 callback.onThumbnailLoaded(bitmap, index);
    114             } else {
    115                 LoadBitmapTask task = mRequests.get(index);
    116                 if (task == null || task.isCancelled()) {
    117                     // no normal task or prefetch for the position, create a new task
    118                     task = new LoadBitmapTask(index, callback);
    119                     mRequests.put(index, task);
    120                     task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
    121                 } else {
    122                     // update existing ResultCallback which might be normal task or prefetch
    123                     task.mResultCallback = callback;
    124                 }
    125             }
    126         }
    127         if (mLastRequestedIndex != index) {
    128             if (mLastRequestedIndex != -1) {
    129                 prefetch(mLastRequestedIndex, index > mLastRequestedIndex);
    130             }
    131             mLastRequestedIndex = index;
    132         }
    133     }
    134 
    135     protected void prefetch(int hintIndex, boolean forward) {
    136         for (Iterator<Map.Entry<Integer, Bitmap>> it =
    137                 mPrefetchCache.snapshot().entrySet().iterator(); it.hasNext(); ) {
    138             Map.Entry<Integer, Bitmap> entry = it.next();
    139             if (forward ? entry.getKey() < hintIndex : entry.getKey() > hintIndex) {
    140                 mPrefetchCache.remove(entry.getKey());
    141             }
    142         }
    143         int inc = forward ? 1 : -1;
    144         for (int i = hintIndex; (mRequests.size() + mPrefetchCache.size()
    145                 < mPrefetchCache.maxSize()) && (inc > 0 ? i < mSeekPositions.length : i >= 0);
    146                 i += inc) {
    147             Integer key = i;
    148             if (mCache.get(key) == null && mPrefetchCache.get(key) == null) {
    149                 LoadBitmapTask task = mRequests.get(i);
    150                 if (task == null) {
    151                     task = new LoadBitmapTask(key, null);
    152                     mRequests.put(i, task);
    153                     task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
    154                 }
    155             }
    156         }
    157     }
    158 
    159     @Override
    160     public void reset() {
    161         for (int i = 0; i < mRequests.size(); i++) {
    162             LoadBitmapTask task = mRequests.valueAt(i);
    163             task.cancel(true);
    164         }
    165         mRequests.clear();
    166         mCache.evictAll();
    167         mPrefetchCache.evictAll();
    168         mLastRequestedIndex = -1;
    169     }
    170 
    171     @Override
    172     public String toString() {
    173         StringBuilder b = new StringBuilder();
    174         b.append("Requests<");
    175         for (int i = 0; i < mRequests.size(); i++) {
    176             b.append(mRequests.keyAt(i));
    177             b.append(",");
    178         }
    179         b.append("> Cache<");
    180         for (Iterator<Integer> it = mCache.snapshot().keySet().iterator(); it.hasNext();) {
    181             Integer key = it.next();
    182             if (mCache.get(key) != null) {
    183                 b.append(key);
    184                 b.append(",");
    185             }
    186         }
    187         b.append(">");
    188         b.append("> PrefetchCache<");
    189         for (Iterator<Integer> it = mPrefetchCache.snapshot().keySet().iterator(); it.hasNext();) {
    190             Integer key = it.next();
    191             if (mPrefetchCache.get(key) != null) {
    192                 b.append(key);
    193                 b.append(",");
    194             }
    195         }
    196         b.append(">");
    197         return b.toString();
    198     }
    199 }
    200