What are the proper dimensions for a background image in an android app?

I would like to create a background image for my app in Photoshop. I understand that I will need to create three differe开发者_如何学Gont files at the appropriate dpi for ldpi, mdpi and hdpi. But what are the appropriate dimensions and resolutions for each?

Dimension varies by phone. Android will scale them slightly. Check out Android Developer's site.