What is the relationship between the Surface and SurfaceHolder in the Android graphics system?

In the Android graphics system, a Surface is an abstract concept that represents a window where images can be drawn and processed. It can be used to display both 2D and 3D graphics, as well as handle user input.

The SurfaceHolder is an interface for the Surface that provides methods and operations for accessing the Surface. With the SurfaceHolder, you can obtain the Canvas object of the Surface for drawing images, and also set properties of the Surface such as format, size, and more.

The SurfaceHolder can be thought of as a gateway to the Surface, providing an interface for interacting with it. It allows access to the Surface instance, which can then be used for drawing graphics with a Canvas object, or for performing other operations and managing the Surface.

In short, SurfaceHolder acts as a proxy interface for Surface, allowing access and manipulation of the Surface.