AKSegmentedControl 设置默认选中项

 
   //WorkDiarySegmentViewController 是自己封装AKSegmentedControl的类
   _segment = [[WorkDiarySegmentViewController alloc]init];//AKSegmentedControl初始化放到 init 否则。。
   _segment.segment.selectedIndexes = [[NSIndexSet alloc]initWithIndex:0];//