Android - Memory leak when dynamically building UI with image resource backgrounds

Question

I have an Activity that I swear is leaking memory. The app I'm working on does a lot with images, so I've had to be pretty stingy with memory when working directly with Bitmaps. I added an Activity, and now if you use this new Activity it basically puts me over the edge with mem usage and I end up throwing the "Bitmap exceeds VM budget" exception. If you never launch this Activity, everything is smooth as it was previously.

I started reading about memory leaks, and I think that I have a similar situation to what is described in the article in the Android docs. I'm dynamically creating a bunch of image views and adding a BackgroundDrawable from the resources and adding an OnClickListener as well. I imagine I have to do some cleanup when the Activity hits onPause in its life cycle, but I'd like to know specifically what is the correct way.

Here is the code that should demonstrate the objects I'm working with...

    LinearLayout templateContainer;
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    ImageView imgTemplatePreview = (ImageView) item.findViewById(R.id.imgTemplatePreview);
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    imgTemplatePreview.setBackgroundDrawable(getResources().getDrawable(previewId));
    imgTemplatePreview.setOnClickListener(imgClick);
    templateContainer.addView(item); 

Answer 1

Rich,

If you are going to be dealing with that many Bitmaps you should aggressively clean them up when they are not needed (onPause is a good start).

I remember a discussion from a long time ago about ImageViews and their odd behavior with lingering references to their displayed bitmaps. From what I do recall is that you should remove all references to the current context from the ImageView if you are going to keep the layout alive but don't want to leak. Remove the onClick listener and bitmap. Call .recycle() on the Bitmap if you want to aggressively free memory. Make sure you don't have any static fields with lingering references to the context or inner class references to it.

The code for Android's launcher was also mentioned during this as a good reference where they do some of these things. OpenSource is your friend.

EDIT

Found Romain Guys article. Basicly he mentions this part of the way though

This example is one of the simplest cases of leaking the Context and you can see how we worked around it in the Home screen’s source code (look for the unbindDrawables() method) by setting the stored drawables’ callbacks to null when the activity is destroyed.

Now I've never had to manage this type of memory usage (yet) so from here I suggest looking at The Home Screen Source for more details. You'll find their unbind() method on line 620