https://qooah.com/2011/12/19/%e7%99%be%e5%ba%a6%e6%89%8b%e6%a9%9f%e7%a5%9e%e7%a7%98%e6%9b%9d%e5%85%89%ef%bc%8c%e6%90%ad%e8%bc%89-android-%e4%bc%bc%e7%9a%84%e4%bd%9c%e6%a5%ad%e7%b3%bb%e7%b5%b1/