Android: only the original thread that created a view hierarchy can touch its views when calling invalidate()

user_4188097 0
Viewed 20393

I'm trying to play a gif using the Movie object and it requires me to call the invalidate() method. However whenever I call this method I get the following error: 

android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

How do I fix this and why is it happening

invalidation android
6 Answers

in case you need it in Kotlin:

val handler = Handler(Looper.getMainLooper())
    handler.post({
        invalidate()
    })
user_22328740

I know this is an older question and the answers here already work but I had an issue with just using Handler because by default android studio uses the wrong Handler object. I had to specify android.os.Handler ie:

final android.os.Handler handler=new android.os.Handler(Looper.getMainLooper());
    handler.post(new Runnable() {
        @Override
        public void run() {
            do_your_ui_stuff_here
            }
        });
user_100106880

There's actually a method in the Android SDK you can use to run invalidate() on the UI thread without having to make your own runnable or handler manually, see the official docs here.

public void postInvalidate ()

Cause an invalidate to happen on a subsequent cycle through the event loop. Use this to invalidate the View from a non-UI thread.

This method can be invoked from outside of the UI thread only when this View is attached to a window.

user_53225820
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