https://qooah.com/2012/07/11/%e6%9c%89%e6%b6%88%e6%81%af%e6%8c%87-google-%e7%82%ba-nexus-7-%e6%8f%90%e4%be%9b-android-4-1-1-%e6%9b%b4%e6%96%b0/