How do I ensure another Thread's Handler is not null before calling it?

Question

My program threw a NullPointerException the other day when it tried to use a Handler created on another thread to send that thread a message. The Handler created by the othe

Answer 1

I just want to add that the checked answer is the best one but if you test it like that is not going to work becouse you need to call super on run methode since it's in charge of preparing the looper so the code should be like this:

private void setUp() {
  mHandlerThread = new CustomThread("foo", Process.THREAD_PRIORITY_BACKGROUND);
  mHandlerThread.start();

  // Create our handler; this will block until looper is initialised
  mHandler = new CustomHandler(mHandlerThread.getLooper());
  // mHandler is now ready to use
}

private class CustomThread extends HandlerThread {
   public void run() {
    super.run() // <- VERY IMPORTANT OTHERWISE IT DOES NOT WORK
    // your code goes here
   }
}   

private class CustomHandler extends Handler {
CustomHandler(Looper looper) {
    super(looper);
}

 @Override
 public void handleMessage(Message msg) {
    // ...
 }

}