https://qooah.com/2011/01/24/android-3-0%e5%88%b0%e5%ba%95%e8%83%bd%e5%90%a6%e5%9c%a8%e6%99%ba%e8%83%bd%e6%89%8b%e6%a9%9f%e4%b8%8a%e6%8e%a1%e7%94%a8%ef%b9%96/