https://qooah.com/2012/04/06/google-%e6%88%96%e6%8e%a8%e5%87%ba%e7%b6%b2%e4%b8%8a%e5%95%86%e5%ba%97%e4%bb%a5%e5%a2%9e%e5%8a%a0-android-%e5%b9%b3%e6%9d%bf%e9%9b%bb%e8%85%a6%e9%8a%b7%e9%87%8f/