https://qooah.com/2012/03/02/android-%e7%85%a7%e7%89%87%e4%b9%9f%e5%8f%af%e8%a2%ab%e6%89%80%e6%9c%89%e7%a8%8b%e5%ba%8f%e8%a8%aa%e5%95%8f-google-%e8%80%83%e6%85%ae%e7%b5%a6%e6%87%89%e7%94%a8%e7%a8%8b%e5%ba%8f%e8%a8%ad%e7%bd%ae/