Question

hi all i have a problem i want to make the UI thread to wait untill a service has been finished can any one tell me how to acheive this?

Answer 1

I’m going to assume you already have the service setup correctly for communicating with your Activity.

You can use a Semaphore to block the UI thread while the service is executing. There are many ways to do this, but for sake of simplicity, this Semaphore could be a static field in a utility class.

public class UtilityClass {
   public static final Semaphore LOCK = new Semaphore(0);
}

In your UI Thread you would do something like: UtilityClass.LOCK.acquire()

In your service, when done you would release the lock: UtilityClass.LOCK.release()

Keep in mind that a few more checks might be necessary to ensure there are no bugs in this approach. You will want to have a look at the Semaphore documentation. For example, before releasing a permit you might want to check that there are zero availablePermits()

I think that answers you question, but please be warned that blocking on the UI thread will cause the app to become unresponsive. In other words, this approach is not best practice and should be avoided.