Control whether the surface view's surface is placed on top of its window. Normally it is placed behind the window, to allow it to (for the most part) appear to composite with the views in the hierarchy. By setting this, you cause it to be placed above the window. This means that none of the contents of the window this SurfaceView is in will be visible on top of its surface.

Note that this must be set before the surface view's containing window is attached to the window manager.

Calling this overrides any previous call to

控制这个surfaceView是否被放在窗口顶层。通常,为了使它与绘图树整合,它被放在窗口之后。通过这个函数，你可以使SurfaceView被放在窗口顶层。这意味着它所在的窗口的其他内容都不可见。(注:可以设置surfaceView透明来使其他内容可见)

这个函数必须在窗口被添加到窗口管理器之前设置。