How to quit HandlerThread's looper safely

Question

I have a HandlerThread, to which I keep posting a runnable every 5 seconds. Something like this:

HandlerThread thread = new HandlerThread("MyThread");
thread.start();
Handler handler = new Handler(thread.getLooper());
handler.post(new Runnable() {
  public void run() { 
    //...
    handler.postDelayed(this, 5000);
  }
});

I need to quit the looper at some point, after 60 seconds or something like that.. so I write:

mainHandler = new Handler(Looper.myLooper()); //main thread's
mainHandler.postDelayed(new Runnable() {
  @Override
  public void run() {
    thread.getLooper().quit();
  }
}, 60000);

I think this causes the looper to quit abruptly, so I start getting this "warning" messages:

W/MessageQueue(3726): java.lang.RuntimeException: Handler (android.os.Handler) {4823dbf8} sending message to a Handler on a dead thread

I want to avoid this error msg, I thought that I could solve it by using the Looper.quitSafely() method.. but I checked the API and it's no longer available. Does anyone know what happened to it? (It's not deprecated like some other methods).

Is there some way I can quit the looper safely? Thanks!

Demagnetize

stop sending handler.postDelayed(this, 5000) delayed Runnables – Ivanivana

like using a flag or something? – Demagnetize

maybe you could try thread.getLooper().quitSafely()? – Volumed

Answer 1

You could try to use a boolean to know if the code should be executed. Something like this:

private boolean runHandler = true;

...

HandlerThread thread = new HandlerThread("MyThread");
thread.start();
Handler handler = new Handler(thread.getLooper());
handler.post(new Runnable() {
    public void run() { 
        if(runHandler){   
            //...
            handler.postDelayed(this, 5000);
        }
    }      
});

mainHandler = new Handler(Looper.myLooper()); //main thread's
mainHandler.postDelayed(new Runnable() {
    @Override
    public void run() {
        runHandler = false;
    }
}, 60000);

Ceramist

what if I have many many handlerthreads though? I mean I wouldn't wanna keep one boolean for each thread...:P – Demagnetize

Yes, in that case you should look for a way to stop the Handler. I guess Handler->removeCallbacks would work if the message is in queue, but if the Handler is being executed I'm not sure if that would stop the execution. – Ceramist

Sorry for not being more useful, but I'm not an expert in threading and Handlers ;) – Ceramist

You can access global variables too. – Ceramist

Answer 2

Im not Thread Guru, but this way can give you direction:

 ...
_thread.setRunning(true);
_thread.start();

 ..

 public void stopThread(){
    boolean retry = true;
    _thread.setRunning(false);
    while (retry) {
        try {
            _thread.join();
            retry = false;
            Log.e("test", "thread stopped");
        } catch (InterruptedException e) {
            Log.e("test", "can't stop thread, retrying...");
            // we will try it again and again...
        }
    }
}

In your thread:

while (isRunning) {
   //...
 }

1st all you implement run method in loop (while(isRunnig){}).

On finish, you switch flag to false and "wait" for join.

Inversion