Object not locked by thread before notify() in onPostExecute

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I try to notify adapters of listviews of main class in onPostExecute but I receive the error: java.lang.IllegalMonitorStateException:object not locked by thread before notify()

@Override
protected void onPostExecute(String result) {
    popularfragment.adapter.notifyDataSetChanged();
    recentfragment.adapter.notifyDataSetChanged();
}

java Object not locked by thread before notify() in onPostExecute android multithreading

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asked Jun 12 '14 at 13:38

Erkan Erol

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2 Answers

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The .notify() method has to be called from within a synchronized context, ie from inside a synchronized block.

The java.lang.IllegalMonitorStateException is thrown when you call .notify() on an object that is not used as the lock for the synchronized block in which you call notify. For example, the following works;

synchronized(obj){
    obj.notify();
}

But this will throw the exception;

synchronized(obj){
    // notify() is being called here when the thread and 
    // synchronized block does not own the lock on the object.
    anotherObj.notify();        
}

Reference;

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edited May 23 '17 at 11:55

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answered Jun 12 '14 at 13:48

Object not locked by thread before notify() in onPostExecute

Rudi Kershaw

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I had the same error, but (for me) the answer suggested by Rudi Kershaw wasn't the issue... I called the notify() of a Notification the wrong way (see the last line of both snippets):

Not working:

public void update() {
    mBuilder.setSmallIcon(R.drawable.ic_launcher)
            .setPriority(AesPrefs.getInt(R.string.PRIORITY_NOTIFICATION_BATTERY, NotificationCompat.PRIORITY_MAX))
            .setOngoing(true);
    mBuilder.setWhen(AesPrefs.getLong(Loader.gStr(R.string.LAST_FIRED_BATTERY_NOTIFICATION) + Const.START_CLIPBOARD_NOTIFICATION_DELAYED, -1));
    mManager.notify(); // <- lil' mistake
}

Working:

public void update() {
    mBuilder.setSmallIcon(R.drawable.ic_launcher)
            .setPriority(AesPrefs.getInt(R.string.PRIORITY_NOTIFICATION_BATTERY, NotificationCompat.PRIORITY_MAX))
            .setOngoing(true);
    mBuilder.setWhen(AesPrefs.getLong(Loader.gStr(R.string.LAST_FIRED_BATTERY_NOTIFICATION) + Const.START_CLIPBOARD_NOTIFICATION_DELAYED, -1));
    mManager.notify(Const.NOTIFICATION_CLIPBOARD, mBuilder.build()); // <- ok ;-)
}

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answered Dec 29 '15 at 20:19

Object not locked by thread before notify() in onPostExecute