Question

I have a problem in some devices like Galaxy Nexus, where if you keep opening activities, you hit out of memory error. I thought I had some memory leaks which prevent activities from collected, but I couldn’t find it. So I wrote this small activity (purely for test purpose.)

public class Test extends Activity {    
    private byte[] imageData = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            Button iv = new Button(this);
            imageData = new byte[1024 * 1024 * 2];
            iv.setText("Open");
            iv.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View v) {
                            startActivity(new Intent(Test.this, Test.class));
                    }
            });
            setContentView(iv);
    }
}

So basically, it allocates 2MB of memory, and you can open another instance of the same activity. On Galaxy S and Kindle Fire, if you keep opening, memory usage increases to a certain point, and then it starts destroying old activities for new activities.

However on Galaxy Nexus, it just goes up until 64MB and crashes with out of memory error.

So is there something I do not know about android memory management, or is this a bug on some devices? If it’s a bug, how can I work around it?

Thank you.

Answer 1

I asked Dianne Hackborn about this (one of the Android framework engineers), and here’s the advice she gave:

The point at which old activities are destroyed is an arbitrary
number, based on the total number of activities across the entire
system. This has always been the case. Relying on activities being
destroyed to reclaim memory like that is never going to be stable; the
activity manager doesn’t know anything about the amount of RAM in a
process or the limit on its RAM or how much RAM a new activity is
going to take to actually have an idea when it should try to destroy
activities in each process.

In other words: You can’t rely on the system destroying Activities as a means of memory management within your own app. You still need to be frugal about memory usage, and have your activities clean up their own memory usage when possible.

In this case, it might be wise to deallocate your memory once onStop() or onPause() is called.