Android Fragments on Backstack taking up too much memory

Question

PROBLEM:

I have an Android application that allows a user to browse to a user\'s profile ViewProfileFragment. Inside ViewProfile

Answer 1

It turns out that fragments share the same lifecycle as their parent activity. According to the Fragment documentation:

A fragment must always be embedded in an activity and the fragment's lifecycle is directly affected by the host activity's lifecycle. For example, when the activity is paused, so are all fragments in it, and when the activity is destroyed, so are all fragments. However, while an activity is running (it is in the resumed lifecycle state), you can manipulate each fragment independently.

So the step that you took to clean up some resources in onPause() of the fragment wouldn't trigger unless the parent activity pauses. If you have multiple fragments that are being loaded by a parent activity then most likely you are using some kind of mechanism for switching which one is active.

You might be able to solve your issue by not relying on the onPause but by overriding setUserVisibleHint on the fragment. This gives you a good place to determine where to do your setup of resources or clean up of resources when the fragment comes in and out of view (for example when you have a PagerAdapter that switches from FragmentA to FragmentB).

public class MyFragment extends Fragment {
  @Override
  public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (isVisibleToUser) {
      //you are visible to user now - so set whatever you need 
      initResources();
    }
    else { 
     //you are no longer visible to the user so cleanup whatever you need
     cleanupResources();
    }
  }
}

As was already mentioned you are stacking items up on a backstack so it's expected that there will be at least a little bit of a memory footprint but you can minimize the footprint by cleaning up resources when the fragment is out of view with the above technique.

The other suggestion is to get really good at understanding the output of the memory analyzer tool (MAT) and memory analysis in general. Here is a good starting point. It is really easy to leak memory in Android so it's a necessity in my opinion to get familiar with the concept and how memory can get away from you. It's possible that your issues are due to you not releasing resources when the fragment goes out of view as well as a memory leak of some kind so if you go the route of using setUserVisibleHint to trigger cleanup of your resources and you still see a high-volume of memory being used then a memory leak could be the culprit so make sure to rule them both out.