Android Out of Memory Exception & Paused Activities

Issue

I'm currently working on an android app with several activities. Most of the time, the app works fine, but from time to time an Out of Memory Exception occurs. (usually when trying to load the large background image for the next activity)

I couldn't find any obvious memory leaks, so I created a heap dump when the exception occurred (like described here) and tried to analyse it with MAT. I haven't done something like this before, so I wasn't sure what exactly I should be looking for. I started clicking through the larger byte objects and the second one seems to be a Bitmap belonging to an ImageButton:

The Path to GC roots shows me an com.android.internal.policy.impl.PhoneWindow instance:

The thing is, the only ImageButton in my whole application is in my launch activity and between that launch activity and the crashing activity are at least 2 more activities.

So why is this image still in the heap?? The ImageButton is simply defined in the layout xml file using the android:src attribute, nothing is done via Code there. There are also a lot of other smaller objects from earlier activities in the heap.

I also wrote a little HelloWorld application and took a look in the heap dump of it and it seems, that android keeps the objects of previous activities in the heap. If this is the case, then an Out of Memory Exception has to be thrown some day, so I guess something must be wrong on my analysis :/

Solution

You might want to look at Bitmap managing in the developer's documentation.

In particular: a bitmap is kept in memory as long as a reference exists to it. So, if you absolutely have to use large bitmaps for your buttons (as you are describing) you might be do better by loading it manually and using recycle as soon as your Activity disappears from sight.

Answered By - DigCamara