https://qooah.com/2011/03/15/android-%e9%96%8b%e7%99%bc%e5%95%86%e6%8e%a7%e5%88%b6%e5%8f%b0%e6%9b%b4%e6%96%b0-%e5%bc%b7%e5%8c%96%e4%ba%86%e7%b5%b1%e8%a8%88%e5%8a%9f%e8%83%bd/