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
17package com.example.android.supportv7.graphics;
18
19import android.graphics.Bitmap;
20import android.os.AsyncTask;
21import android.provider.MediaStore;
22import android.support.v4.graphics.BitmapCompat;
23import android.support.v4.os.AsyncTaskCompat;
24import android.support.v4.util.LruCache;
25import android.widget.ImageView;
26
27/**
28 * A very naive lazily implemented image loader. Do not use this in production code.
29 */
30class ImageLoader {
31
32    /**
33     * A LruCache used to store images which has a maximum size of 10% of the maximum heap size.
34     */
35    private static final BitmapCache CACHE = new BitmapCache(
36            Math.round(Runtime.getRuntime().maxMemory() / 10));
37
38    private ImageLoader() {
39    }
40
41    interface Listener {
42        void onImageLoaded(Bitmap bitmap);
43    }
44
45    static void loadMediaStoreThumbnail(final ImageView imageView,
46            final long id,
47            final Listener listener) {
48
49        final Bitmap cachedValue = CACHE.get(id);
50        if (cachedValue != null) {
51            // If the image is already in the cache, display the image,
52            // call the listener now and return
53            imageView.setImageBitmap(cachedValue);
54            if (listener != null) {
55                listener.onImageLoaded(cachedValue);
56            }
57            return;
58        }
59
60        AsyncTaskCompat.executeParallel(new AsyncTask<Void, Void, Bitmap>() {
61            @Override
62            protected Bitmap doInBackground(Void... params) {
63                return MediaStore.Images.Thumbnails.getThumbnail(
64                        imageView.getContext().getContentResolver(),
65                        id,
66                        MediaStore.Images.Thumbnails.MINI_KIND,
67                        null);
68            }
69
70            @Override
71            protected void onPostExecute(Bitmap bitmap) {
72                imageView.setImageBitmap(bitmap);
73
74                if (bitmap != null) {
75                    // Add the image to the memory cache first
76                    CACHE.put(id, bitmap);
77
78                    if (listener != null) {
79                        listener.onImageLoaded(bitmap);
80                    }
81                }
82            }
83        });
84    }
85
86    /**
87     * A simple cache implementation for {@link android.graphics.Bitmap} instances which uses
88     * {@link android.support.v4.util.LruCache}.
89     */
90    private static class BitmapCache extends LruCache<Long, Bitmap> {
91        BitmapCache(int maxSize) {
92            super(maxSize);
93        }
94
95        @Override
96        protected int sizeOf(Long key, Bitmap value) {
97            return BitmapCompat.getAllocationByteCount(value);
98        }
99    }
100
101}
102