LruBitmapCache.java

package your.awesome.app;

import android.graphics.Bitmap;
import android.support.v4.util.LruCache;
import com.android.volley.toolbox.ImageLoader.ImageCache;

public class LruBitmapCache extends LruCache<String, Bitmap> implements ImageCache {

	public LruBitmapCache(int maxSize) {
		super(maxSize);
	}
	
	@Override
	protected int sizeOf(String key, Bitmap value) {
		return value.getRowBytes() * value.getHeight();
	}
	
	@Override
	public Bitmap getBitmap(String url) {
		return get(url);
	}

	@Override
	public void putBitmap(String url, Bitmap bitmap) {
		put(url, bitmap);
	}

}

Could you indicate how to provided a correct maxSize value? I think it was indicated three screens worth? How is that calculated in Android? Thanks

It would be something like this:

public int getCacheSize() {
    final DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();
    final int screenWidth = displayMetrics.widthPixels;
    final int screenHeight = displayMetrics.heightPixels;
    final in screenBytes = screenWidth * screenHeight * 4; // 4 bytes per pixel

    return screenBytes * 3;
}

maxSize for caches that do not override sizeOf(K, V), this is the maximum number of entries in the cache. http://developer.android.com/reference/android/util/LruCache.html#LruCache(int) or int maxSize = (int) (Runtime.getRuntime().maxMemory() / 1024 / 8);

@ArnaudCourbiere

You can take a look here at the code of the Google way of do this:
http://developer.android.com/training/volley/request.html

After all I think it depends on how you use volley. It makes sense on apps like Instagram or Google Play Store where you have the screen full of images. If you use Volley for request images but you have 1 or 2 images in each activity and they are not really loaded heavily... I have no idea how to work on this cache image stuff. Probably a few MB is enough.