How static inner class with a WeakReference to the outer class can Avoid Android Memory Leaks? Need an example

Question

I was studying this article, Avoid Memory Leaks. There are few suggestions to avoid memory leaks, one of them is below:

Avoid non-static inner classes in an activity if you don't control their life cycle, use a static inner class and make a weak reference to the activity inside. The solution to this issue is to use a static inner class with a WeakReference to the outer class, as done in ViewRoot and its W inner class for instance

1- Can some one elaborate this by giving an example?

2- How to use to static inner classes with Weak-reference to the inner classes?

3- what are the best practices to use that static class in your application to Avoid Memory leaks.

Great thanks.

Answer 1

In this post, an answer shows a simple example of what you are looking for: How to instantiate interface in fragment?

BUT, one problem is that sometimes a Fragment lives longer than its Activity, for example, if the Activity has a config change (e.g. rotated) then the Activity is destroyed, but the Fragment can be kept alive and then reattached to the new (rotated) Activity. See this post: Android Fragment lifecycle over orientation changes

So you might have a problem with the proposed solution using the WeakReference, because after a rotation you would have a reference to the old Activity (or maybe nothing).

What seems to work for me:

1) When I need a ref to the Activity, call getActivity(). Can do this right in onPostExecute() of a member AsyncTask class, for example.

2) Check the result for null (this can happen: Fragments can live longer than their Activities)

3) Check if activity isFinishing() – you don’t want to do certain UI things in that state.

4) Cast activity to your interface type.

5) Call callback in interface type.