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      1 /*
      2  * Copyright (C) 2014 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.supportv7.graphics;
     18 
     19 import android.graphics.Bitmap;
     20 import android.os.AsyncTask;
     21 import android.provider.MediaStore;
     22 import android.support.v4.graphics.BitmapCompat;
     23 import android.support.v4.util.LruCache;
     24 import android.widget.ImageView;
     25 
     26 /**
     27  * A very naive lazily implemented image loader. Do not use this in production code.
     28  */
     29 class ImageLoader {
     30 
     31     /**
     32      * A LruCache used to store images which has a maximum size of 10% of the maximum heap size.
     33      */
     34     private static final BitmapCache CACHE = new BitmapCache(
     35             Math.round(Runtime.getRuntime().maxMemory() / 10));
     36 
     37     private ImageLoader() {
     38     }
     39 
     40     interface Listener {
     41         void onImageLoaded(Bitmap bitmap);
     42     }
     43 
     44     static void loadMediaStoreThumbnail(final ImageView imageView,
     45             final long id,
     46             final Listener listener) {
     47 
     48         final Bitmap cachedValue = CACHE.get(id);
     49         if (cachedValue != null) {
     50             // If the image is already in the cache, display the image,
     51             // call the listener now and return
     52             imageView.setImageBitmap(cachedValue);
     53             if (listener != null) {
     54                 listener.onImageLoaded(cachedValue);
     55             }
     56             return;
     57         }
     58 
     59         new AsyncTask<Void, Void, Bitmap>() {
     60             @Override
     61             protected Bitmap doInBackground(Void... params) {
     62                 return MediaStore.Images.Thumbnails.getThumbnail(
     63                         imageView.getContext().getContentResolver(),
     64                         id,
     65                         MediaStore.Images.Thumbnails.MINI_KIND,
     66                         null);
     67             }
     68 
     69             @Override
     70             protected void onPostExecute(Bitmap bitmap) {
     71                 imageView.setImageBitmap(bitmap);
     72 
     73                 if (bitmap != null) {
     74                     // Add the image to the memory cache first
     75                     CACHE.put(id, bitmap);
     76 
     77                     if (listener != null) {
     78                         listener.onImageLoaded(bitmap);
     79                     }
     80                 }
     81             }
     82         }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
     83     }
     84 
     85     /**
     86      * A simple cache implementation for {@link android.graphics.Bitmap} instances which uses
     87      * {@link android.support.v4.util.LruCache}.
     88      */
     89     private static class BitmapCache extends LruCache<Long, Bitmap> {
     90         BitmapCache(int maxSize) {
     91             super(maxSize);
     92         }
     93 
     94         @Override
     95         protected int sizeOf(Long key, Bitmap value) {
     96             return BitmapCompat.getAllocationByteCount(value);
     97         }
     98     }
     99 
    100 }
    101