1.contentresolver call方法的使用
http://www.mamicode.com/info-detail-883422.html
2.volatile
http://www.importnew.com/24082.html
https://www.cnblogs.com/shangxiaofei/p/5564047.html
https://www.cnblogs.com/dengzz/p/5688021.html
3.volatile boolean和atomicboolean的区别