Runnable is posted successfully but not run

Question

In an existing Android project I\'ve encountered the following piece of code (where I inserted the debugging litter)

ImageView img = null;

public void onCre         


        

Answer 1

I think the problem is you are updating the UI (ImageView) with a separate thread, which is not the UI Thread. The UI can only be updated by the UI Thread.

You can solve this by using Handler:

Handler uiHandler;

public void onCreate(){
    ...
    uiHandler = new Handler(); // This makes the handler attached to UI Thread
    ...
}

Then replace your:

if ( !img.post(new Runnable() {

with

uiHandler.post(new Runnable() {

to make sure the imageview is updated in the UI Thread.

Handler is a quite confusing concept, I also took hours of research to really understand about this ;)