Android - Custom AlertDialog Background Color

Question

So I see we can have alertdialogs with gray and white (when setinverse...) background colors.

To learn why I checked themes.xml of the sdk, checking it I was led to

Answer 1

so easy..

Dialog d=builder2.create();
...
d.show();
d.getWindow().setBackgroundDrawableResource(R.drawable.mydialog_shape);