什么是ViewOverlay？ ViewOverlay is a class that we can find in Android since its version 4.3 (API version 18) that provides a transparent layer on top of a View, to which you can add visual content and that does not affect the layout hierarchy. It always has the same size and position as its host view, allowing you to add content over that view. 运行效果 红色部分：使用了 按钮的 parent-parent layout (the main, first-level, layout) ViewGroupOverlay，所以可以穿越整个画面。 ...