Question

I have three buttons in on screen,when i click each button it navigate to corresponding button contends.i need to change part of the screen without changing whole screen.Can anyone give an idea about this.

Thank You

Answer 1

Generally speaking if you modify a manager you should invalidate that manager which is the way to tell the device a repaint is required.

http://www.blackberry.com/developers/docs/4.0.2api/net/rim/device/api/ui/Manager.html#invalidate()

Edit: information about adding to/deleting from VerticalFieldManager
The documentation specific to a VerticalFieldManager is here:
http://www.blackberry.com/developers/docs/3.7api/net/rim/device/api/ui/container/VerticalFieldManager.html

The methods you should use to update its child fields are all inherited from the Manager class. You can also see a list of other subclasses here:
http://www.blackberry.com/developers/docs/3.7api/net/rim/device/api/ui/Manager.html

E.g. Check the methods for delete, deleteAll, deleteRange, insert, add.