Question

I’ve recently run into a snag while putting on the finishing touches for my BlackBerry app. I’m building a login screen which, if the user is successful in logging in, goes to a data loading screen, and then to a home screen. From the home screen, you can use the app. Everything works great but one thing, I can’t seamlessly move from the login screen to the loading screen, to the home screen. I can move from the login screen to the loading screen ok, because I’m doing that via a button click which is on the GUI thread, but then I have the login screen at the bottom of the stack and can’t get it out using the dismiss method. Once in the loading screen, I can’t push the home screen because I’m not doing it via the gui method, though I’m able to update the GUI via the following piece of code:

   private void checkData(){

            Timer loadingTimer = new Timer();
    TimerTask loadingTask = new TimerTask()
    {

        public void run()
        {
            // set the progress bar
            progressGaugeField.setValue(DataManager.getDataLoaded());

            // for repainting the screen
            invalidate();
        }
    };
    loadingTimer.scheduleAtFixedRate(loadingTask, 500, 500);
}

Does anyone know how to solve my problem of moving seamlessly from the login screen to the loading screen to the home screen? Note: once I’m at the home screen I’d like to have it be the only screen on the stack.

Thanks!

Answer 1

In this case, you may want to push the home screen of your application first and then push the login screen after it. I am not sure of your situation, but here are the assumptions I am making:

• you are storing login information
• if login information is not stored, you push the login screen
• in a success case, you store login information and proceed to show the home screen
• if login fails or is canceled, you don’t display the home screen

If these assumptions are reasonably valid, the below code should work nicely for you.

public class YourApp extends UiApplication {
public YourApp() {
    final AppHomeScreen screen = new AppHomeScreen();
    pushScreen(screen);

    if(getLoginInfo() == null) {
        final LoginScreen loginScreen = new LoginScreen();
        this.invokeLater(new Runnable() {
            public void run() {
                pushModalScreen(loginScreen);
                if(getLoginInfo()==null)
                    popScreen(screen); //exit the app
                }
                //perhaps the loading screen populates info in your home screen then pops itself
                pushScreen(new LoadingScreen(screen));
            }
        );
    }
}