Handlers in Android Programming

Question

Hello All!

I have got to know that the Handlers are basically used to Run the Small Section of Code and etc...

But I didn't got the exact scenerio about when particularly It is Ideal to use the Handlers!

Any Help???

Thanks, david

Answer 1

Handlers are used for updating the UI from other (non-UI) threads.

For example, you can declare a Handler on your Activity class:

Handler h = new Handler();

Then you have some other tasks on different thread that wants to update some UI (progress bar, status message, etc). This will crash:

progressBar.setProgress(50);

Instead, call this:

h.post(new Runnable() { 
    public void run() {
         progressBar.setProgress(50);
    }
});

Answer 2

I'm a newbie myself but I'll give a newbie example since I recently learned this, I'm sure there are many more.

You have to use a Handler when you want to update the main UI when you are doing something in another thread. For example in my case I used it in image slideshow code that runs in a TimerTask. You cannot update the main UI ImageView with the next image from within the TimerTask because it's in a different thread. So you have to use a Handler or you get an error.

This is just one example. I hope this helps.