Waiting for asynchronous callback in Android's IntentService

Question

I have an IntentService that starts an asynchronous task in another class and should then be waiting for the result.

The problem is that the IntentSer

Answer 1

I agree with corsair992 that typically you should not have to make asynchronous calls from an IntentService because IntentService already does its work on a worker thread. However, if you must do so you can use CountDownLatch.

public class MyIntentService extends IntentService implements MyCallback {
    private CountDownLatch doneSignal = new CountDownLatch(1);

    public MyIntentService() {
        super("MyIntentService");
    }

    @Override
    protected final void onHandleIntent(Intent intent) {
        MyOtherClass.runAsynchronousTask(this);
        doneSignal.await();
    }

}

@Override
public void onReceiveResults(Object object) {
    doneSignal.countDown();
}

public interface MyCallback {

    public void onReceiveResults(Object object);

}

public class MyOtherClass {

    public void runAsynchronousTask(MyCallback callback) {
        new Thread() {
            public void run() {
                // do some long-running work
                callback.onReceiveResults(...);
            }
        }.start();
    }

}