A safer Android Handler for use with Activities or other components that require posting back on to the UI thread via an Activity reference.

UIHandler.java

public abstract class UIHandler<T extends Activity> extends Handler {
  private final WeakReference<T> mRef;
  
  public UIHandler(T a) {
    mRef = new WeakReference<>(a);
  }

  @Override
  public void handleMessage(Message msg) {
    final T a = mRef.get();
    if (a == null || a.isFinishing()) {
      return;
    }
    handleMessage(msg, a);
  }
  
  abstract void handleMessage(Message msg, final T activity);
}