Create memory cache for android

How to add memory cache to android applications for performance improvements.

This android video tutorial explains how to create memory cache for android. Using this method will have a dramatic effect on performance for android applications.

Implementation

Create LruCache

final int maxMemorySize = (int) Runtime.getRuntime().maxMemory() / 1024;
 final int cacheSize = maxMemorySize / 10;

 mMemoryCache = new LruCache<String, Bitmap>(cacheSize) {

     @Override
     protected int sizeOf(String key, Bitmap value) {
         return value.getByteCount() / 1024;
     }
 };

Create cache getters & setters

public static Bitmap getBitmapFromMemoryCache(String key) {
      return mMemoryCache.get(key);
  }

  public static void setBitmapToMemoryCache(String key, Bitmap bitmap) {
      if(getBitmapFromMemoryCache(key) == null) {
          mMemoryCache.put(key, bitmap);
      }
  }

Add bitmap to cache in AsyncTask doInBackground method

@Override
 protected Bitmap doInBackground(File... params) {
     // return BitmapFactory.decodeFile(params[0].getAbsolutePath());
     mImageFile = params[0];
     // return decodeBitmapFromFile(params[0]);
     Bitmap bitmap = decodeBitmapFromFile(mImageFile);
     CamaraIntentActivity.setBitmapToMemoryCache(mImageFile.getName(), bitmap);
     return bitmap;
 }

Check for Bitmap in cache in RecyclerView adapter

@Override
  public void onBindViewHolder(ViewHolder holder, int position) {
      File imageFile = imagesFile.listFiles()[position];
      Bitmap bitmap = CamaraIntentActivity.getBitmapFromMemoryCache(imageFile.getName());
      if(bitmap != null) {
          holder.getImageView().setImageBitmap(bitmap);
      }
      else if(checkBitmapWorkerTask(imageFile, holder.getImageView())) {
          BitmapWorkerTask bitmapWorkerTask = new BitmapWorkerTask(holder.getImageView());
          AsyncDrawable asyncDrawable = new AsyncDrawable(holder.getImageView().getResources(),
                  placeHolderBitmap,
                  bitmapWorkerTask);
          holder.getImageView().setImageDrawable(asyncDrawable);
          bitmapWorkerTask.execute(imageFile);
      }
  }

Conclusion

Implementing memory cache will normally be simple & straight forward, which will result in significant & visible performance improvements. But care does need to be taken in deciding the size of the cache, if too large out of memory errors will result.