Question

The spacebar has a default action on many UI fields: click for buttonfield, select/unselect for checkbox, scrolling on a verticalfieldmanager.

My screen has a listfield with more than 20 rows. When the user hits the spacebar, I want the listfield to scroll.

For example, BlackBerry default calendar app, when we hit spacebar, it will scroll down.
and BlackBerry default text Messages, when we hit spacebar, it will scroll down.

is this a default property? or do I need to write code for spacebar key?

Answer 1

You have to create a custom key listener:

private class CustomKeyListener implements KeyListener {

    public boolean keyChar(char key, int status, int time) {
        if(key == Characters.SPACE){
            //TODO handle key here
            //WARNING: this code runs on event thread!
            return true;
        } 

        return false;
    }

    public boolean keyDown(int keycode, int time) {         
        return false;
    }

    public boolean keyRepeat(int keycode, int time) {
        return false;
    }

    public boolean keyStatus(int keycode, int time) {
        return false;
    }

    public boolean keyUp(int keycode, int time) {
        return false;
    }       
}

Then call Mainscreen.addKeyListener with an instance of your key listener as parameter.

From there you can change your manager (main manager or nested one) scroll with the Manager.setVerticalScroll method. If you want to increment it, you can retrieve the current scroll calling Manager.getVerticalScroll and then add a fixed value. In case you don’t have a nested VerticalFieldManager in your screen, you can try with your screen’s default, which you can obtain calling Mainscreen.getMainManager.

UPDATE:
For List fields, you can call ListField.getSelectedIndex and ListField.setSelectedIndex to change elements, but this is not an smooth scrolling. But if you placed the list field inside a VerticalFieldManager, you can change the manager scroll as described above.