InsetDrawable

InsetDrawable is a wrapper drawable in the Android framework that applies padding around another drawable by insetting its drawing area. It holds a reference to a child drawable and four inset values: left, top, right, and bottom. When drawn, it computes a drawing rectangle by reducing the bounds by the insets and delegates rendering to the child within that rectangle. It also forwards state changes and size information to the inner drawable.

Construction and usage: In code, an InsetDrawable is created with a child drawable and the four inset values, for example new InsetDrawable(inner, left, top, right, bottom). It can also be defined in XML as an inset element that specifies the insets and contains a nested drawable as its content. The inner drawable’s state, padding, and behavior are preserved, while the visible area is restricted by the specified insets. InsetDrawable is compatible with all drawable types and can be used wherever a drawable resource is needed, such as backgrounds, icons, or elements inside a LayerDrawable.

Behavior and capabilities: The insets effectively reduce the drawable’s drawing area without changing the inner drawable’s intrinsic size. Insets can be adjusted programmatically at runtime via setter methods, allowing dynamic padding changes. InsetDrawable forwards the inner drawable’s padding and optical bounds, and respects its state changes during interactions.

Related concepts: InsetDrawable is related to other drawable wrappers such as LayerDrawable and StateListDrawable, and is useful for adding padding without altering the underlying drawable resource.