Android Avoid memory leaks with Anonymous Class, Handler, Timer Task, Thread


Example


In android, every developer uses Anonymous Class (Runnable) at least once in a project. Any Anonymous Class has a reference to its parent (activity). If we perform a long-running task, the parent activity will not be destroyed until the task is ended.
Example uses handler and Anonymous Runnable class. The memory will be leak when we quit the activity before the Runnable is finished.

  new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            // do abc long 5s or so
        }
    }, 10000); // run "do abc" after 10s. It same as timer, thread...

How do we solve it?

  1. Dont do any long operating with Anonymous Class or we need a Static class for it and pass WeakReference into it (such as activity, view...). Thread is the same with Anonymous Class.
  2. Cancel the Handler, Timer when activity is destroyed.