Apps some begins question

[goldE]

hi
i have some begin programming question

1. how to change my program icon by code ?
2. how to make 2 screen to my program and if i press button1
i'll see screen2 and if i'll press back button i'll see screen1 ?
3. how to read and wright text file that in phone path ?

thanks in advance

 

[miXer]

all of these thing you can find answers to on the sdk site here: The Developer's Guide | Android Developers