【android】SurfaceFlinger (surface composer)

最新推荐文章于 2025-03-02 11:36:57 发布

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SurfaceFlinger是Android系统服务，负责将应用和系统表面复合成单个缓冲区，最终由显示控制器显示。本文深入探讨SurfaceFlinger的工作原理，包括系统级服务特性、UI更新机制及资源消耗原因。同时，解释了SurfaceFlinger与OpenGL的关系，以及其在UI绘制和复合过程中的作用。

SurfaceFlinger is an Android system service, responsible for compositing all the application and system surfaces into a single buffer that is finally to be displayed by display controller.

Let's zoom in above statement.

SurfaceFlinger is a system wide service but it is not directly available to application developer as Sensor or other services can be. Every time you want to update your UI, SurfaceFlinger will kick in. This explains why SurfaceFlinger is a battery drainer.

Besides your application surfaces, there are system surfaces, including status bar, navigation bar and, when rotation happens, surfaces created by the system for rotation animation. Most applications have only one active surface - the one of current foreground activity, others have more than one when SurfaceView is used in the view hierarchy or Presentation mode is used.

SurfaceFlinger is responsible for COMPOSITING all those surfaces. A common misunderstanding is that SurfaceFinger is for DRAWING. It is not correct. Drawing is the job of OpenGL. The interesting thing is SurfaceFlinger used openGL for compositing as well.

The composition result will be put in a system buffer, or native window, which is the source for display controller to fetch data from. This is what you see in the screen.