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I have this what seems like a very tedious task of rescheduling a Timer along with TimerTask to enable my service/ongoing process to execute at different times...i have tried searching many forums including this example which seems to have worked for this person but when i try the same code in my service, i get the following error:

03-04 14:21:41.204: E/AndroidRuntime(336): FATAL EXCEPTION: Timer-0

03-04 14:21:41.204: E/AndroidRuntime(336): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

Does anyone know what this error means, and what can be a possible solution? from what i researched online about this error: it usually happens when im trying to do UI changes, on a non-UI thread...in my case, all i do is send a notification and then call a reScheduleTimer function like in that example...

any input is appreciated...

EDIT: here is the code where its blowing up:

    public void reScheduleTimer(long duration) {
    Log.v(TAG, "Inside reScheduleTimer");
    timer.cancel();
    timer = new Timer("profileSwitcherTimer", true); 
    timerTask = new MyTimerTask(); <----
    timer.schedule(timerTask, duration);
}

here is the MyTimerTask class:

public class MyTimerTask extends TimerTask{
private Handler updateUI = new Handler(){
        public void dispatchMessage(Message msg) {
            Toast.makeText(getApplicationContext(), "Timer Ran", Toast.LENGTH_LONG).show();
        }
}

public void run() {
    ....code that i want execute
    showNotification();
    reScheduleTimer(60000);
}

}

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Parag Thuse
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  • Can you post the code block where that exception is being thrown? It would be more helpful if we could see what you have written already. – Robert Mar 04 '12 at 19:41
  • @Robert: Edited original post with snippets of code that im working with... – Parag Thuse Mar 04 '12 at 19:57

1 Answers1

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You're creating the Handler on a thread that does not have a message loop. As the Looper documentation says:

Threads by default do not have a message loop associated with them; to create one, call prepare() in the thread that is to run the loop, and then loop() to have it process messages until the loop is stopped.

One way to fix this would be to explicitly bind you Handler instance to a particular Looper, by using the Handler constructor that takes one. The easiest would be to just use the main looper for the application; you can get it thourgh the static Looper.getMainLooper() method. The drawback is that this will bind your handler to the UI thread, which by itself is not that bad, as long as you don't do too long operations on it; otherwise your UI will become unresponsive.

Franci Penov
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  • omg...i couldnt believe it..i must have spent a lot of time trying to understand why this started blowing up all of a sudden...in the Handler, all i was doing was outputing a Toast message...what i dont get is how does it blow up even when i dont call updateUI.. – Parag Thuse Mar 04 '12 at 20:23
  • The constructor of the `TimerTask` instance invokes implicitly the constructor for the `updateUI` handler, and that results in the crash. – Franci Penov Mar 05 '12 at 03:20