1. SurfaceView的创建和销毁
当SurfaceView隐藏时,SurfaceView被销毁,此时会调用SurfaceHolder.Callback.surfaceDestroyed()
当SurfaceView再次显示时,SurfaceView被创建,此时会调用SurfaceHolder.Callback.surfaceCreated()
2. SurfaceView的叠加显示
如果有两个SurfaceView需要叠加时,例如,A要悬浮在B之上,
此时,需要对A调用SurfaceView.setZOrderOnTop(true);