Sometimes it is not a good option to use several Screens, it is better to have only one Screen and several VerticalArrangements.
In this example, it gets a random temperature Centigrades and a incremental random distance Kilometers and shows in Label1 and Label2.

- In other window (it is a VerticalArrangement2) we can choose Fahrenheit and miles.
- If user chooises ºF or miles, code convert by expressions.
- We use 2 VerticalArrengement with Height and Width: fill parent.
- VerticalArrangement1 = Button, Label components to show information
- VerticalArrangement2 = CheckBox components to choice C, F, km and miles.
- By Property Visible shows VerticalArrangement1 or VerticalArrangement2


- [careful in this example: before " km", " miles", " ºC", " ºF" there is a space]
- Regards.
Juan Antonio Villalpando
http://kio4.com/appinventor/23G_datos_pantalla_config2.htm (It is in Spanish).