Android Handler Memory Leaks

Dima Voronkevych from Bumble's Android team reveals how a simple postDelayed() call can silently keep 7 Activity instances alive in memory. Even with garbage collection, your app might be one rotation away from an OutOfMemoryError.

This deep dive from Bumble's engineering team dissects Android Handler memory leaks using real heap dumps and OQL analysis. The article walks through progressively better solutions, from static inner classes to a custom library that solves the problem elegantly.

Key Takeaways

• Anonymous Runnables create indirect this$0 references that prevent Activity garbage collection
• Static classes with WeakReferences work but create unreadable boilerplate code
• Handler.removeCallbacksAndMessages(null) in onDestroy clears all pending messages cleanly
• Bumble's WeakHandler library prevents leaks while keeping code readable and maintainable

The article includes detailed heap dump analysis showing exactly how Message queues chain back to the main thread and why WeakHandler's dual reference strategy is so clever.