Android Graphic designing

I'm developing a simple app with a customized background and a button in the middle.
I've got the whole different resolutions for different screens down, but do all the versions of the background need to be 9patches? How do I take into consideration the always there android top navigation bar and the possible use of advertisements at the bottom? Do they just cover the design or do they change the resolution?
 
Android Graphic designing
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I'm developing a simple app with a customized background and a button in the middle.
I've got the whole different resolutions for different screens down, but do all the versions of the background need to be 9patches? How do I take into consideration the always there android top navigation bar and the possible use of advertisements at the bottom? Do they just cover the design or do they change the resolution?
 