Hello Fennec-devs,
While monitoring some memory issues last week, I ran into this. We had a piece
of code for resetting the image in an ImageView:
imageView.setImageBitmap(null);
This did the intended thing. The image was cleared, and the UI showed no
problems.
But under the hood, Android does:
@android.view.RemotableViewMethod
public void setImageBitmap(Bitmap bm) {
// if this is used frequently, may handle bitmaps explicitly
// to reduce the intermediate drawable object
setImageDrawable(new BitmapDrawable(mContext.getResources(), bm));
}
As you can see, there is no check on whether “bm” is null or not. This creates
a “BitmapDrawable” object. The BitmapDrawable internally creates “State”
objects and “Paint” objects. All of these aren’t even going to be used, as we
are just clearing up the image in the view. Now think of resetting the
ImageView (like favicon), whenever the row goes out of visible area inside a
list (recycling). With a small scroll, we would be creating endless objects
while recycling. (HORRORRR!!!) So, instead of using setImageBitmap(), please
use setImageDrawable() in such cases.
Note: setImageResource(android.R.color.transparent) is also valid. But, Android
decodes the resource in the UI thread, and might not be good for performance
purposes.
Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=934001
Thanks,
Sriram.
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