| 1 | public class ImageLoader { |
| 2 | // 图片缓存 |
| 3 | LruCache< String , Bitmap > mImageCache ; |
| 4 | // 线程池，线程数量为 CPU 的数量 |
| 5 | ExecutorService mExecutorService = Executors . newFixedThreadPool( Runtime . getRuntime() . availableProcessors()) ; |
| 6 | |
| 7 | // 构造方法 |
| 8 | public ImageLoader () { |
| 9 | // 初始化图片缓存 |
| 10 | initImageCache() ; |
| 11 | } |
| 12 | |
| 13 | private void initImageCache () { |
| 14 | // 计算可使用的最大内存 |
| 15 | final int maxMemory = ( int ) ( RunTime . getRuntime() . maxMemory() / 1024 ) ; |
| 16 | // 取四分之一的可用内存作为缓存 |
| 17 | final int cacheSize = maxMemory / 4 ; |
| 18 | |
| 19 | mImageCache = new LruCache< String , Bitmap > (cacheSize) { |
| 20 | // 重写 LruCache 的 sizeOf 方法 |
| 21 | @Override |
| 22 | protected int sizeOf ( String key , Bitmap bitmap ) { |
| 23 | return bitmap . getRowBytes() * bitmap . getHeight() / 1024 ; |
| 24 | } |
| 25 | } ; |
| 26 | } |
| 27 | |
| 28 | /** |
| 29 | * 显示图片 |
| 30 | */ |
| 31 | public void displayImage ( final String url , final ImageView imageView ) { |
| 32 | imageView . setTag(url) ; |
| 33 | // 使用线程池 |
| 34 | mExecutorService . submit( |
| 35 | new Runnable () { |
| 36 | @Override |
| 37 | public void run () { |
| 38 | Bitmap bitmap = downloadImage(url) ; |
| 39 | if ( null == bitmap) return ; |
| 40 | if (imageView . getTag() . equals(url)) |
| 41 | imageView . setImageBitmap(bitmap) ; // 显示下载的图片 |
| 42 | // 存入缓存 |
| 43 | mImageCache . put(url, bitmap) ; |
| 44 | } |
| 45 | } |
| 46 | ) ; |
| 47 | } |
| 48 | |
| 49 | /** |
| 50 | * 下载图片，在显示图片方法中调用 |
| 51 | */ |
| 52 | public Bitmap downloadImage ( String imageUrl ) { |
| 53 | Bitmap bitmap = null ; |
| 54 | try { |
| 55 | URL url = new URL (imageUrl) ; |
| 56 | final HttpURLConnection conn = ( HttpURLConnection ) url . openConnection() ; |
| 57 | bitmap = BitmapFactory . decodeStream(conn . getInputStream()) ; |
| 58 | conn . disconnect() ; |
| 59 | } catch ( Exception e){ |
| 60 | e . printStackTrace() ; |
| 61 | } |
| 62 | return bitmap ; |
| 63 | } |
| 64 | } |
