代理方法 //标题 -(NSString*)segmentView:(XMFSegmentView*)segmentViewtitleOfIndex:(NSUInteger)index; //每个item的宽度 -(CGFloat)segmentView:(XMFSegmentView*)segmentViewwidthOfIndex:(NSUInteger)index; //item的数量 -(NSUInteger)numberOfItemsInSegmentView:(XMFSegmentView*)segmentView; //点击item