What is the rendering process of Android View?

The rendering process of Android View can be divided into the following steps:

1. Measurement: In this step, the View will determine its dimensions by calling the measure() method. During the process, the View’s measurement width and height will be determined based on the layout parameters (such as width, height) and the constraints of the parent container.
2. Layout: In this step, the View will determine its position in the parent container by calling the layout() method. During the layout process, the View’s position will be determined based on its measured width, measured height, and the layout conditions of the parent container.
3. Drawing: In this step, the View will draw its own content by calling the draw() method. The content to be drawn will be determined based on the View’s size, style, background, and other attributes.
4. Dispatch: During this step, the View will distribute drawing to child Views by calling the dispatchDraw() method. The child Views will be drawn in the order of measurement and layout.
5. Invalidate: When the content of the View changes or needs to be redrawn, you can call the invalidate() method to notify the View to redraw. Redrawing will trigger the above-mentioned process of measuring, laying out, and drawing.

It is important to note that the above process is being executed on the UI thread, so performing time-consuming operations during the rendering of the view may result in lagging interface. To avoid this situation, the time-consuming operations can be executed on a separate thread, and then the results can be passed back to the UI thread for updating.