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POAndroid: DiskLruCache not saved after application closed
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  1. POAndroid: DiskLruCache not saved after application closed
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    copied!<p>I'm new to SO and also new to Android programming! So pardon me if the question is trivial.</p> <p>Anyway, I'm trying to create a gallery application that will show the thumbnails of all media files (videos and pictures) in a folder. My application is running good except for the long waiting time to process the image to get its sampled bitmap. </p> <p>I've settled this using memory cache (LruCache) but it only solves the problem when user stays in the app and navigate around. Everytime the user closes the app and re-opens it, it'll re-generate the cache again.</p> <p>After doing some readings online, I decided to add disk cache on top of memory cache, hoping that it'll solve the problem. But even after I implemented it, the problem still persists. Not sure if I'm doing it wrong. </p> <p>Below is my code to initialize the memory cache and disk cache.</p> <pre><code>protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); String path = Environment.getExternalStorageDirectory().getAbsolutePath(); if (savedInstanceState != null) { displayManager.cancelAsyncTask(); path = savedInstanceState.getString(ARG_POSITION); }else{ // Get memory class of this device, exceeding this amount will throw an // OutOfMemory exception. final int memClass = ((ActivityManager)getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass(); // Use 1/8th of the available memory for this memory cache. final int cacheSize = 1024 * 1024 * memClass / 8; mMemoryCache = new LruCache&lt;String, Bitmap&gt;(cacheSize) { protected int sizeOf(String key, Bitmap bitmap) { // The cache size will be measured in bytes rather than number of items. return bitmap.getByteCount(); } }; Log.d("DEBUG_CACHE","context is "+this); File cacheDir = getDiskCacheDir(this, DISK_CACHE_SUBDIR); Log.d("DEBUG_CACHE", "cache dir is "+cacheDir.getAbsolutePath()); new InitDiskCacheTask().execute(cacheDir); } ArrayList&lt;File&gt; folderList = dataManager.getFolderListWithPhotoOrVideo(path); ArrayList&lt;File&gt; thumbList = dataManager.getAllPhotosAndVideos(path); displayManager.setCurrentPath(path); displayManager.setParent(this); displayManager.setMemCache(mMemoryCache); displayManager.setFolderList(folderList); displayManager.setThumbnails(thumbList); } </code></pre> <p>Below is how I get the thumbnails from cache if exists and how I add the bitmap to the cache.</p> <pre><code>@Override protected Void doInBackground(Void... params) { int noOfThumbnails = thumbnails.size(); for(int j=0;j&lt;noOfThumbnails;j++){ String filePath = thumbnails.get(j).getName(); if(isPhoto(filePath)){ //if file is an image file Uri uri = Uri.fromFile(new File(thumbnails.get(j).getAbsolutePath())); Bitmap thumb = getBitmapFromMemCache(filePath); if(thumb==null){ thumb = getBitmapFromDiskCache(filePath); if(thumb==null){ thumb = getPreview(uri); addBitmapToCache(filePath,thumb); } } bitmaps.add(thumb); }else{ Bitmap thumb = getBitmapFromMemCache(filePath); if(thumb==null){ thumb = getBitmapFromDiskCache(filePath); if(thumb==null){ thumb = ThumbnailUtils.createVideoThumbnail(thumbnails.get(j).getAbsolutePath(),MediaStore.Images.Thumbnails.MICRO_KIND); addBitmapToCache(filePath,thumb); } } bitmaps.add(thumb); } double progress = ((double)(j+1)/(double)noOfThumbnails)*100; publishProgress(new Double(progress).intValue()); if(isCancelled()){ Log.d("DEBUG", "doInBackGround. Task cancelled"); return null; } } return null; } public void addBitmapToCache(String key, Bitmap bitmap) { if (getBitmapFromMemCache(key) == null) { mMemoryCache.put(key, bitmap); } // Also add to disk cache synchronized (parent.mDiskCacheLock) { try { if (parent.mDiskLruCache != null &amp;&amp; parent.mDiskLruCache.get(key) == null) { parent.mDiskLruCache.put(key, bitmap); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } public Bitmap getBitmapFromMemCache(String key) { return (Bitmap) mMemoryCache.get(key); } public Bitmap getBitmapFromDiskCache( String key ) { Bitmap bitmap = null; Snapshot snapshot = null; try { snapshot = parent.mDiskLruCache.get( key ); if ( snapshot == null ) { return null; } final InputStream in = snapshot.getInputStream( 0 ); if ( in != null ) { final BufferedInputStream buffIn = new BufferedInputStream( in, Utils.IO_BUFFER_SIZE ); bitmap = BitmapFactory.decodeStream( buffIn ); } } catch ( IOException e ) { e.printStackTrace(); } finally { if ( snapshot != null ) { snapshot.close(); } } return bitmap; } </code></pre> <p>For the DiskLruCache.java, I used the google source file (can be found <a href="https://code.google.com/p/iosched/source/browse/android/src/com/google/android/apps/iosched/util/DiskLruCache.java?r=fcd13b09ef50f290dc0681ebec74fbdfcac969a5" rel="nofollow">here</a>).</p>
 

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