添加自定义类
https://blog.csdn.net/suchfool/article/details/38758367
https://blog.csdn.net/liukai6/article/details/78580913
全局自定义方法
https://www.cnblogs.com/fps2tao/p/7846065.html
https://blog.csdn.net/a8725585/article/details/73770304
自定义常量
https://blog.csdn.net/qq_16399991/article/details/56676755
https://i.cnblogs.com/EditPosts.aspx?postid=9165855&update=1