https://blog.csdn.net/lyz_zyx/article/details/80868930
dongzhong/TestForFloatingWindow: 相关博客《Android悬浮窗的实现》
https://github.com/dongzhong/TestForFloatingWindow
Android Demo : 悬浮窗(支持Android7.0) - 简书
https://www.jianshu.com/p/ac63c57d2555
https://blog.csdn.net/qq_28468727/article/details/52144155