Java Development

[anicangu]

What is the difference between pushscreen and popscreen?

I am trying to make the flow of screen using this piece of code to pass to next screen,

UiApplication.getUiApplication().invokeLater(new Runnable(){
     public void run() {
         UiApplication.getUiApplication().pushScreen(nextScreen);
     }
});

but I noted previous screen is still opened even if nextScreen is pushed.

What should be right way to swich screens?

[arkadyz · Accepted solution]

Displayed Screens in BlackBerry UI Applications are kept in a stack, called Screen stack. The top of the stack is so called "active Screen" - the only Screen which can get user's input. Screens which are closer to the top obscure those deeper down.

pushScreen puts a (previously undisplayed - otherwise it will throw an exception) Screen on top of the Screen stack, which makes it active. popScreen removes the activeScreen (if no parameters are given - this functionality is deprecated) or the specified Screen (if displayed - again, will throw an exception otherwise) from the Screen stack. If the top (active) Screen is popped, the one below it becomes the top one - accepting user's input and unobscured.

That's it! Design your application the way you see fit, but with this picture in mind.

[Astarot82]

With pushScreen() you'll push a Screen into the stack. If you pop a Screen, you're removing it from the stack.

I think your problem is that can't push a Screen in top of the others if you don't pop it before.

[jprofitt]

I'm not sure if I read Astarot's post correctly -- it's been a long week already -- but want to make sure that it's clear that you can push more than one screen onto the stack (i.e., you don't have to pop a screen before you push another screen). Are you getting any Exceptions when you try to push the screen? Also, could you possibly post a little more code, like what is making this call just in case the bug is actually in another part of the program.