java.lang.OutOfMemoryError: bitmap size exceeds VM budget

One of the most common errors that I found developing Android Apps is the

java.lang.OutOfMemoryError: Bitmap Size Exceeds VM Budget

error. I found this error frequently on Activities using lots of bitmaps after changing orientation: the Activity is destroyed, created again and the layouts are “inflated” from the XML consuming the VM memory available for bitmaps.

Bitmaps on the previous Activity layout are not properly deallocated by the garbage collector because they have crossed references to their activity. After many experiments I found a quite good solution for this problem.

First, set the “id” attribute on the parent view of your XML layout:

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/RootView">
        ...

Then, on the onDestroy() method of your Activity, call the unbindDrawables() method passing a reference to the parent View and then do a System.gc().

    @Override
    protected void onDestroy() {
        super.onDestroy();

        unbindDrawables(findViewById(R.id.RootView));
        System.gc();
    }

    private void unbindDrawables(View view) {
        if (view.getBackground() != null) {
            view.getBackground().setCallback(null);
        }
        if (view instanceof ViewGroup) {
            for (int i = 0; i < ((ViewGroup) view).getChildCount(); i++) {
                unbindDrawables(((ViewGroup) view).getChildAt(i));
            }
            ((ViewGroup) view).removeAllViews();
        }
    }

This unbindDrawables() method explores the view tree recursively and:

1. Removes callbacks on all the background drawables
2. Removes childs on every viewgroup