https://qooah.com/2012/03/21/android-%e6%96%bc-2011-%e7%ac%ac%e5%9b%9b%e5%ad%a3%e4%b8%ad%e5%9c%8b%e6%99%ba%e8%83%bd%e6%a9%9f%e9%8a%b7%e9%87%8f%e4%bd%94-7-%e6%88%90/