See Also: ScaleDrawable Members
A Drawable that changes the size of another Drawable based on its current level value. You can control how much the child Drawable changes in width and height based on the level, as well as a gravity to control where it is placed in its overall container. Most often used to implement things like progress bars.
It can be defined in an XML file with the <scale> element. For more information, see the guide to Drawable Resources.