How to send MIDlet to background on Symbian
This articles shows how to use setCurrent(null) to send a foreground application to the background.
The setCurrent(null doesn't set the displayable to null but is used in Java ME implementations that support concurrent applications like S60 to send the foreground application to background (on Series 40 phones this approach does not work). The application that is shown is the last application that was shown before the MIDlet got activated. For example, if user launched the MIDlet from application shell just before then application shell is shown.
Following code can be used to send MIDlet to background:
Display display = Display.getDisplay(myMIDletClass);