https://qooah.com/2012/12/21/%e6%88%91%e5%80%91-android-%e6%89%8b%e6%a9%9f%e5%8c%96%e8%ba%ab%e8%bf%bd%e8%b9%a4%e5%99%a8%e8%bf%bd%e8%b9%a4%e8%81%96%e8%aa%95%e8%80%81%e4%ba%ba/