https://qooah.com/2011/07/13/%e6%90%b6%e5%85%88%e8%a9%a6%e7%94%a8-%e6%9c%ac%e7%b6%b2%e8%ae%93%e4%bd%a0%e4%b8%8b%e8%bc%89%e6%9c%80%e6%96%b0%e7%89%88-android-market/