https://qooah.com/2016/04/11/android-n-%e6%b8%ac%e8%a9%a6%e8%a8%88%e5%8a%83%e5%8f%af%e8%83%bd%e6%93%b4%e5%a4%a7%e5%88%b0%e9%9d%9e-nexus-%e8%a8%ad%e5%82%99/