Android background sizes and density

Does anyone know what the dimensions should be for creating a background for android application?

开发者_如何学PythonI want to have a background to look HD on all screen sizes.

Is there a guideline for this, or a reference?

You can reach this only by using vector graphics. All other image types will lose quality when you scale them up or down.

Android tries to manage different screens itself by using graphics with different resolution and dpi (drawable-hdpi, -mdpi, -ldpi). I recommend reading the article below or use vector graphics.

Supporting Multiple Screens: http://developer.android.com/guide/practices/screens_support.html