GradientDrawable

GradientDrawable is an Android framework drawable that renders shapes filled with color gradients. It can produce linear, radial, or sweep gradients and can be used as a background for views or as icons. As a subclass of Drawable, it combines shape properties with gradient rendering, making it a common tool for custom UI skins without bitmap resources.

A GradientDrawable supports multiple gradient types, including linear, radial, and sweep, and an orientation for linear gradients (for example, TOP_BOTTOM or LEFT_RIGHT). It can interpolate between colors using a start color, end color, and an optional center color, or accept an array of colors. The drawable also supports different shapes such as rectangle, oval, line, and ring, and allows per-corner or uniform corner radii to create rounded corners. Additional styling options include a stroke for an outline, with optional dash patterns, as well as an explicit size and a radial gradient radius for radial gradients. A useLevel flag enables gradient changes in response to level-based animations.

GradientDrawable can be defined in XML or created programmatically. In XML, it is typically declared as a shape with a nested gradient element specifying type, colors, and optionally angle, centerColor, and gradientRadius. In code, you can instantiate it with a constructor like new GradientDrawable(orientation, colors), then set its shape, corners, stroke, and other properties at runtime. It is widely used for customizable backgrounds, buttons, and other UI components where scalable, resolution-independent visuals are desired. API coverage is broad across Android versions, with support for all core features described above.