https://qooah.com/2014/05/17/%e3%80%90%e6%95%99%e5%ad%b8%e3%80%91%e6%89%8b%e6%a9%9f%e6%9b%b4%e5%ae%89%e5%85%a8-android-pattern-lock-%e5%8a%a0%e5%bc%b7%e5%a4%a7%e6%b3%95/