Switch pages/classes in BlackBerry

I am currently developing a blackberry app. the scenario is when a user clicks on a menu item, it will go to another page. Currently there are 3 classes, MyApp, SecondPage and MyScreen. the codes below belongs to SecondPage.

From MyApp, I am trying to pushScreen to SecondPage after the user clicks on a MenuItem but I'm unable to do so because it(SecondPage) is extending UiApplication am I right? but if I change it to extend MainScreen, it cant pushScreen(_screen). any suggestions please?

Thanks, Hend

class MyApp extends UiApplication{

//creating a member variable for the MainScreen
MainScreen _screen= new MainScreen();
//string variables to store the values of the XML document
String _node,_element;
Connection _connectionthread;

public static void main(String arg[]){
    MyApp application = new MyApp();
    //create a new instance of the application
    //and start th开发者_JS百科e application on the event thread
    application.enterEventDispatcher();
}

public MyApp() {
    _screen.setTitle("Agenda");//setting title
    //_screen.add(new RichTextField("Requesting....."));
    _screen.add(new SeparatorField());
    pushScreen(_screen); // creating a screen
    //creating a connection thread to run in the background
    _connectionthread = new Connection();
    _connectionthread.start();//starting the thread operation
}

    public void updateField(String node, String element) 
{    
    synchronized (UiApplication.getEventLock()) 
    {
        String title = "My App";
        _screen.add(new RichTextField(/*node + " : " +*/ element + "\n" ));
        if (node.equals(title))
        {
            _screen.add(new SeparatorField());
        }
    }
}

Your screens need to inherit from Screen, not from UiApplication. If you look at the docs for UiApplication, you see there is a static method getUiApplication() that will return you a reference to the UiApplication for purposes of pushing screens (among other useful tasks).

So, instead of just pushScreen(_screen) your code would be UiApplication.getUiApplication().pushScreen(_screen).