https://www.jianshu.com/p/1558cbd20d17(不錯)
https://www.jianshu.com/p/fe94636ef3d6
Android ItemDecoration 實現分組索引列表(不錯)
https://www.jianshu.com/p/4230a90cb359
不錯的效果
https://www.jianshu.com/p/24fb8d0aafb0
搜索
Android ItemDecoration打造分組懸浮
分割線,比較好