tabstrip + context questions

Hi all,

I have the following questions :

1. How to check of the context of a node is changed ?

2. I have an application with a tabstrip with 2 tabblads.

In the first tab i have a button : when i cklick to this button it fills the value of a textview with the tekst 'database update.'

My requirment is the following : when i go to the 2nd tab and back to the first tab i want t clear the tekst.

Hoe to do this ?

Thanks