How to remove all callbacks from a Handler?

Solution 1:

In my experience calling this worked great!

handler.removeCallbacksAndMessages(null);

In the docs for removeCallbacksAndMessages it says...

Remove any pending posts of callbacks and sent messages whose obj is token. If token is null, all callbacks and messages will be removed.

Solution 2:

For any specific Runnable instance, call Handler.removeCallbacks(). Note that it uses the Runnable instance itself to determine which callbacks to unregister, so if you are creating a new instance each time a post is made, you need to make sure you have references to the exact Runnable to cancel. Example:

Handler myHandler = new Handler();
Runnable myRunnable = new Runnable() {
    public void run() {
        //Some interesting task
    }
};

You can call myHandler.postDelayed(myRunnable, x) to post another callback to the message queue at other places in your code, and remove all pending callbacks with myHandler.removeCallbacks(myRunnable)

Unfortunately, you cannot simply "clear" the entire MessageQueue for a Handler, even if you make a request for the MessageQueue object associated with it because the methods for adding and removing items are package protected (only classes within the android.os package can call them). You may have to create a thin Handler subclass to manage a list of Runnables as they are posted/executed...or look at another paradigm for passing your messages between each Activity

Hope that Helps!