public void show() {
   if (!currentChildScreen.isActive()) uiStack.pushScreen(currentChildScreen);
   currentChildScreen.setUp();
 }
 public void popScreen() {
   currentChildScreen.popScreen(uiStack, this);
 }
 public void changeScreen(CustomScreen screen) {
   currentChildScreen = screen;
   currentChildScreen.setController(this);
   show();
 }
 protected void onExposed() {
   clearFields();
   layoutScreen();
   super.onExposed();
 }