This article introduces Choreographer, a class that App developers may not frequently encounter but is critically important in the Android Framework rendering pipeline. We will cover the background of its introduction, a brief overview, partial source code analysis, its interaction with MessageQueue, its application in APM (Application Performance Monitoring), and some optimization ideas for Choreographer by mobile phone manufacturers.

Choreographer coordinates pending frame callbacks with display timing; it does not itself set the screen refresh rate. At 120 Hz, the interval is about 8.33 ms. Meeting a frame deadline also depends on CPU scheduling, GPU work, buffers, and composition. Apps request callbacks as needed rather than redraw on every physical Vsync. This article also distinguishes what FrameCallback, FrameMetrics, gfxinfo, Looper, and Perfetto can observe.