content: sub init()
      m.top.observeField("visible", "onVisiblityChange")
  end sub
  
  sub goToSpecificScreen(screenInfoMap as object)
      m.top.getScene().navigateScreen = screenInfoMap
  end sub
  
  sub onVisiblityChange(event)
      if event.getData() = true
          onResume()
      else if event.getData() = false
          onPause()  
      end if
  end sub
  
  sub onResume()
  endsub
  
  sub onPause()
  endsub    