MainScreen not pop after calling popScreen()

I try to pop the main screen using UiApplication.getUiApplication().popScreen(getScreen开发者_开发技巧());

But after executing this line main screen not poped and my application hanged. And I received the following message from console.

FocusHistory: Focus lost; App AppName; Component net.rim.device.api.ui.component.ButtonField

try to use

UiApplication.getUiApplication.popScreen((UiApplication.getUiApplication().getA‌​ctiveScreen())

UiApplication.getUiApplication().popScreen(this);

        Or

UiApplication.getUiApplication().popScreen(UiApplication.getUiApplication().getActiveScreen());