Question

I have an Androd application that talks to a back-end web service. As part of the testing, I need to simulate different lengths of client-side delay when a submit button is pressed.

Right now, I am using a Thread.sleep() in my OnClickListener for my submit button, but sleeping the UI thread like this has the unintended consequence of causing the app to appear to “freeze” completely – the button stays highlighted until the thread wakes up and my ProgressBar is likewise completely frozen. Here is my code:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_checkout);

    pBar = (ProgressBar) findViewById(R.id.progressBar1);
    pBar.setVisibility(View.INVISIBLE);

    Button submitButton = (Button) findViewById(R.id.btnSubmit);
    submitButton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            pBar.setVisibility(View.VISIBLE);
            try {
                Thread.sleep(3000); //eventually this delay will be random
                                    //right now it obviously hangs the UI
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            performMyAppSpecificWorkHere();
            pBar.setVisibility(View.INVISIBLE);
            CheckoutActivity.this.finish();
        }
    });  
}

I’m looking for ways I could simulate a delay without hanging the entire UI. Any ideas are welcome. Thanks!

edit

Some clarification here! Part of what I need to do is make simulate a delay and allow the user interface to handle it cleanly (which is what’s NOT happening now).

ie…if there is a delay on either the client or the web service, the client should handle it by letting the spinner spin while it waits. The ability to simulate a back-end delay is already done and that works the way I want it to, but I want to simulate a delay on the client without hanging the UI thread.

Answer 1

here we go:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_checkout);

    pBar = (ProgressBar) findViewById(R.id.progressBar1);
    pBar.setVisibility(View.INVISIBLE);

    Button submitButton = (Button) findViewById(R.id.btnSubmit);
    submitButton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            Thread t=new Thread(new Runnable(){
               @Override
               public void run(){
                 try {
                  Thread.sleep(3000);
                 } catch (InterruptedException e) {
                   e.printStackTrace();
                 }
                 performMyAppSpecificWorkHere();
                 runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        pBar.setVisibility(View.INVISIBLE);
                        CheckoutActivity.this.finish();
                    }
                 }
               }
            });
            pBar.setVisibility(View.VISIBLE);
            t.start();
        }
    });  
}

So, you are starting a new thread in the onClick event. This new thread should do the application work after sleeping for 3 seconds. After that, you want to update some ui objects, and you can not do that from inside a thread that isn’t the UI Thread. That’s why there is a runOnUiThread(..) after performing the work. Hope it helps!