BlackBerry back to screen detection - blackberry

Question

HI, I try to detect reterning to screen after closing another screen,
should work when returning from my application screens, but also returning from device camera
after shooting video. In overriden method onExposed() I'm able to detect this situation,
but it's called too many times, and also called when dialog was shown (alert).
Is there better way to detect return to screen?
protected void onExposed() {
// return to screen detected
MainApp.addLog("onExposed");
}

Answer 1

returning from device camera after
shooting video
Check the Application.activate()
The system invokes this method when it
brings this application to the
foreground. By default, this method
does nothing. Override this method to
perform additional processing when
being brought to the foreground.

Answer 2

If you override the Screen.onUiEngineAttached(boolean) method, you can be notified when the screen is attached or detached from the UI --- basically when it's pushed or popped from the screen stack.

Answer 3

I had to do a similar thing and found it's very confusing because onExposed() can be called multiple times in uncertain timing.
To detect returning from screen B in screen A (main screen), I used screen B's onUiEngineAttached(false) which is called when it is popped.
To use callback:
public interface Ievent {
public void backFromScreenBEvent();
}
Screen A:
public class ScreenA extends MainScreen implements Ievent
{
private ScreenB screenB;
// constructor
public ScreenA()
{
screenB = new ScreenB(this); // pass over Ievent
// ....
}
public void backFromScreenBEvent()
{
// screen B is returning, do something
}
Screen B:
public final class ScreenB extends MainScreen
{
private Ievent event;
// constructor
public ScreenB(final Ievent event)
{
this.event = event;
// ...
}
protected void onUiEngineAttached(boolean attached) {
super.onUiEngineAttached(attached);
if (!attached) {
event.backFromScreenBEvent(); // notify event
}
}