https://qooah.com/2011/09/02/%e5%b0%bc%e7%88%be%e6%a3%ae%e5%aa%92%e9%ab%94%e7%99%bc%e8%a1%a8%e6%89%8b%e6%a9%9f%e7%a0%94%e7%a9%b6%e5%a0%b1%e5%91%8a-android%e5%a4%a7%e5%8b%9d%e5%88%a9/