iOS Segment滑动居中

1、创建UIScrollView

#pragma mark - 创建Segment
-(UIView *)segmentView{
    
    if (!_segView) {
        _segView = [UIScrollView new];
        _segView.backgroundColor = LYColorWhite;
        _segView.showsHorizontalScrollIndicator = NO;
    }
    return _segView;
    
}

2、添加按钮

for (int i = 0; i < titleArray.count; i ++) {
        
        LYLineButton *btnTitle = [LYLineButton new];
        [btnTitle setTitle:[NSString stringWithFormat:@"%@",titleArray[i]] forState:0];
        [btnTitle setTitleColor:[UIColor blackColor] forState:0];
        btnTitle.titleLabel.font = LYFONT_SISE_16;
        btnTitle.tag = i;
        [btnTitle addTarget:self action:@selector(buttonTitleSelect:) forControlEvents:UIControlEventTouchUpInside];
        [_segView addSubview:btnTitle];
        
        [btnTitle mas_makeConstraints:^(MASConstraintMaker *make) {
            
            if (lastButton) {
                make.left.mas_equalTo(lastButton.mas_right).offset(20);
            }else{
                make.left.mas_equalTo(10);
            }
            make.top.mas_equalTo(0);
            make.height.mas_equalTo(40);
            
        }];
        lastButton = btnTitle;
        
        
        if (i + 1 == titleArray.count) {
            
            [self layoutIfNeeded];
            CGFloat width = lastButton.frame.origin.x + lastButton.frame.size.width;
            _segView.contentSize = CGSizeMake(width + 10, LYHeight(lastButton));
            
        }
        
        //初始化的时候默认选中第一个按钮
        if (i == 0) {
            [btnTitle setTitleColor:LYColorDefualt forState:0];
            btnTitle.lineColor = LYColorDefualt;
        }
        
    }

3、核心代码

for (UIView *subView in self.segView.subviews) {
        if ([subView isKindOfClass:[LYLineButton class]]) {
            LYLineButton *subBtn = (LYLineButton *)subView;
            
            if (subBtn.tag == index) {
                
                //移动对应选择的当前视图显示在中央
                CGRect centerRect = CGRectMake(subBtn.center.x - LYWidth(_segView)/2, 0, LYWidth(_segView), LYHeight(_segView));
                [_segView scrollRectToVisible:centerRect animated:YES];
                
                //选中状态
                if (subBtn.selected) {
                    subBtn.selected = NO;
                }else{
                    subBtn.selected = YES;
                }
                [subBtn setTitleColor:LYColorDefualt forState:0];
                subBtn.lineColor = LYColorDefualt;
                
                //标记通过ScrollView滑动时，不触发下面的动画
                if (stamp) {
                    __weak typeof(self) wSelf = self;
                    [UIView animateWithDuration:0.2 animations:^{
                        wSelf.mainSView.contentOffset = CGPointMake(Screen_Width * subBtn.tag, 0);
                    }];
                }
                
            }else{
                [subBtn setTitleColor:[UIColor blackColor] forState:0];
                subBtn.lineColor = [UIColor clearColor];
            }
        }
    }

4、最最核心代码

CGRect centerRect = CGRectMake(subBtn.center.x - LYWidth(_segView)/2, 0, LYWidth(_segView), LYHeight(_segView));
[_segView scrollRectToVisible:centerRect animated:YES];

5、说明
使用scrollRectToVisible:animated:方法的时候，contentSize的width和height都不能为0，否则不能滚动。