单击按钮时如何更改图像

Question

I am displaying image on when clicking on a Button using interface but the image ic_launcher.png does not show up on the Button after some time the image_all.png is only shown.

• How should I show my first image for some time using sleep and then show image2?
• Should I show both the images on the same button but with time delay.

Any help would be appreciated.

try{
    button1.setBackgroundResource(R.drawable.ic_launcher);
    Thread.sleep(1000); 
} catch(Exception e){

}
button1.setBackgroundResource(R.drawable.images_all);

Answer 1

When you use Thread.sleep(1000); you're actually "stopping" the UI thread, because you're calling sleep(1000); on the UI thread. This causes your application to halt completely for 1 second in your case.

So this isn't such a good idea :-)

Instead you should use something like a Handler for instance. A Handler can be called with a specified delay, so that the action will first be performed after the specified delay. And most importantly, the Handler doesn't "block" the UI thread, as the Thread.sleep(1000); does.

So using a Handler your code, could look something like this instead:

button1.setBackgroundResource(R.drawable.ic_launcher);
Handler uiHandler = new Handler();
uiHandler.postDelayed(new Runnable() {
    @Override
    public void run() {
        button1.setBackgroundResource(R.drawable.images_all);
    }
}, 1000);

Notice the 1000 in the end of postDelayed() which tells the Handler to post this "message" after 1000 milliseconds instead of immediately.

On a side-note: It's not good practice to "eat" the Exceptions like you do in your try-catch .

Answer 2

You should be able to see the R.drawable.ic_launcher change occur. My thoughts about this are around how you're doing the Thread.sleep() . Android isn't fond of performing blocking tasks (such as Thread.sleep) in the UI Thread. When you call the setBackgroundResource and then sleep, the thread that would update the UI is sleeping and cannot perform the update. This is how I would do it instead:

    button1.setBackgroundResource(R.drawable.ic_launcher);

    Handler handler = new Handler();
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            button1.setBackgroundResource(R.drawable.images_all);
        }
    }, 1000);