Apps need help changing bitmap from child class

[powerpoint45]

I need a child class to draw a bitmap given by the parent.Right now, in the child it has:
Bitmap background; and
C.drawbitmap...
I need to find a way to change the bitmap from the parent by doing:
background = BitmapFactory.decodeResource(getResources(), R.drawable.background);

.....so how would i do it?