private LruCache<String, Bitmap> mMemoryCache;  @Override protected void onCreate(Bundle savedInstanceState) {   ...   // Get max available VM memory, exceeding this amount will throw an   // OutOfMemory exception. Stored in kilobytes as LruCache takes an   // int in its constructor.   final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);    // Use 1/8th of the available memory for this memory cache.   final int cacheSize = maxMemory / 8;    mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {     @Override     protected int sizeOf(String key, Bitmap bitmap) {       // The cache size will be measured in kilobytes rather than       // number of items.       return bitmap.getByteCount() / 1024;     }   };   ... }  public void addBitmapToMemoryCache(String key, Bitmap bitmap) {   if (getBitmapFromMemCache(key) == null) {     mMemoryCache.put(key, bitmap);   } }  public Bitmap getBitmapFromMemCache(String key) {   return mMemoryCache.get(key); } 

public void loadBitmap(int resId, ImageView imageView) {   final String imageKey = String.valueOf(resId);    final Bitmap bitmap = getBitmapFromMemCache(imageKey);   if (bitmap != null) {     mImageView.setImageBitmap(bitmap);   } else {     mImageView.setImageResource(R.drawable.image_placeholder);     BitmapWorkerTask task = new BitmapWorkerTask(mImageView);     task.execute(resId);   } } 

class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {   ...   // Decode image in background.   @Override   protected Bitmap doInBackground(Integer... params) {     final Bitmap bitmap = decodeSampledBitmapFromResource(         getResources(), params[0], 100, 100));     addBitmapToMemoryCache(String.valueOf(params[0]), bitmap);     return bitmap;   }   ... } 

private DiskLruCache mDiskLruCache; private final Object mDiskCacheLock = new Object(); private boolean mDiskCacheStarting = true; private static final int DISK_CACHE_SIZE = 1024 * 1024 * 10; // 10MB private static final String DISK_CACHE_SUBDIR = "thumbnails";  @Override protected void onCreate(Bundle savedInstanceState) {   ...   // Initialize memory cache   ...   // Initialize disk cache on background thread   File cacheDir = getDiskCacheDir(this, DISK_CACHE_SUBDIR);   new InitDiskCacheTask().execute(cacheDir);   ... }  class InitDiskCacheTask extends AsyncTask<File, Void, Void> {   @Override   protected Void doInBackground(File... params) {     synchronized (mDiskCacheLock) {       File cacheDir = params[0];       mDiskLruCache = DiskLruCache.open(cacheDir, DISK_CACHE_SIZE);       mDiskCacheStarting = false; // Finished initialization       mDiskCacheLock.notifyAll(); // Wake any waiting threads     }     return null;   } }  class BitmapWorkerTask extends AsyncTask<Integer, Void, Bitmap> {   ...   // Decode image in background.   @Override   protected Bitmap doInBackground(Integer... params) {     final String imageKey = String.valueOf(params[0]);      // Check disk cache in background thread     Bitmap bitmap = getBitmapFromDiskCache(imageKey);      if (bitmap == null) { // Not found in disk cache       // Process as normal       final Bitmap bitmap = decodeSampledBitmapFromResource(           getResources(), params[0], 100, 100));     }      // Add final bitmap to caches     addBitmapToCache(imageKey, bitmap);      return bitmap;   }   ... }  public void addBitmapToCache(String key, Bitmap bitmap) {   // Add to memory cache as before   if (getBitmapFromMemCache(key) == null) {     mMemoryCache.put(key, bitmap);   }    // Also add to disk cache   synchronized (mDiskCacheLock) {     if (mDiskLruCache != null && mDiskLruCache.get(key) == null) {       mDiskLruCache.put(key, bitmap);     }   } }  public Bitmap getBitmapFromDiskCache(String key) {   synchronized (mDiskCacheLock) {     // Wait while disk cache is started from background thread     while (mDiskCacheStarting) {       try {         mDiskCacheLock.wait();       } catch (InterruptedException e) {}     }     if (mDiskLruCache != null) {       return mDiskLruCache.get(key);     }   }   return null; }  // Creates a unique subdirectory of the designated app cache directory. Tries to use external // but if not mounted, falls back on internal storage. public static File getDiskCacheDir(Context context, String uniqueName) {   // Check if media is mounted or storage is built-in, if so, try and use external cache dir   // otherwise use internal cache dir   final String cachePath =       Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()) ||           !isExternalStorageRemovable() ? getExternalCacheDir(context).getPath() :               context.getCacheDir().getPath();    return new File(cachePath + File.separator + uniqueName); }