Question

As I understand it (not that I’m correct) Drawables are generally correctly removed from memory when the application is finished with them. Bitmaps however need to be manually recycled, and sometimes even have a special class written to handle them properly. My question is, in regards to memory and leaks, is it more beneficial to simply stick with Drawables like such:

myView.setBackgroundDrawable(getResources().getDrawable(R.drawable.my_image));
myView1.setBackgroundDrawable(getResources().getDrawable(R.drawable.my_image1));
myView2.setBackgroundDrawable(getResources().getDrawable(R.drawable.my_image2));

rather than something like so with Bitmaps:

Bitmap tmpBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.my_image);
myView.setImageBitmap(tmpBitmap);

tmpBitmap.recycle();
tmpBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.my_image1);
myView1.setImageBitmap(tmpBitmap);

tmpBitmap.recycle();
tmpBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.my_image2);
myView2.setImageBitmap(tmpBitmap);
tmpBitmap.recycle();

I’ve also read of course that you have to be careful about recycle() method on Bitmaps because they can be removed while still in use? It seems like these issues keep popping up in different forms, but I can’t really get a straight answer from anyone on the matter. One person says to reuse a Bitmap and recycle after every use, and others say use Drawables and an unbindDrawables() method (this is what I’ve been using):

private void unbindDrawables(View view) {
    if (view.getBackground() != null) {
        view.getBackground().setCallback(null);
    }
    if (view instanceof ViewGroup) {
        for (int i = 0; i < ((ViewGroup) view).getChildCount(); i++) {
            unbindDrawables(((ViewGroup) view).getChildAt(i));
        }
        ((ViewGroup) view).removeAllViews();
    }
}

Any applicable insight would be much appreciated though. Thanks

Answer 1

I back Romain’s proposal, but I’m not sure your question is addressing your actual problem. I don’t know how you handle the references to your Views. Maybe you simply have memory leaks in your application? A lot of memory leaks in Android are related to Context. When a Drawable is attached to a View, the View is set as a callback on the Drawable.

TextView myView = new TextView(this);
myView.setBackgroundDrawable(getDrawable(R.drawable.my_bitmap));

In the code snippet above, this means the Drawable has a reference to the TextView which itself has a reference to the Activity (the Context) which in turns has references to pretty much anything depending on your code.

Without looking at more of your code I guess you’re on the right track by setting the stored drawables’ callbacks to null when an Activity is destroyed.