之前不同的项目写了好几次，这次想想封装一下，代码虽然不多，但是重复造轮子总不是好习惯。

原理：ScrollView横向滚动，依次排列菜单按钮，以颜色和下划线来标识选择

效果如图中横向菜单栏

实现起来没有复杂逻辑，直接上全套代码：

typedef void(^MenuClickEvent)(NSInteger index);

@interface BDMenuScrollView : UIScrollView
{
    UIView * markLine;
    NSInteger lastIndex;
}

@property(nonatomic) NSInteger selectedIndex;

@property(nonatomic) BOOL repeatTouch;

@property(nonatomic, copy)MenuClickEvent clickBlock;

-(void)setMenuWithArray:(NSArray *)array;

-(void)setButtonSelectedAtIndex:(NSInteger)index;

@end

@implementation BDMenuScrollView
- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        self.showsVerticalScrollIndicator = NO;
        self.showsHorizontalScrollIndicator = NO;
    }
    return self;
}
-(void)setMenuWithArray:(NSArray *)array{
    for (UIView * view in self.subviews) {
        [view removeFromSuperview];
    }
    
    if(array.count){
        CGRect frame = CGRectMake(0, 0, 0, self.frame.size.height);
        for (int i = 0; i<array.count; i++) {
            NSString * titleStr = array[i];
            
            UIButton * button = [[UIButton alloc] initWithFrame:frame];
            [self addSubview:button];
            [button addTarget:self action:@selector(buttonEvent:) forControlEvents:UIControlEventTouchUpInside];
            [button setTitleColor:[UIColor darkGrayColor] forState:UIControlStateNormal];
            [button setTitleColor:[UIColor colorFromHexString_au:@"04ab62"] forState:UIControlStateSelected];
            [button setTitle:titleStr forState:UIControlStateNormal];
            button.titleLabel.font = [UIFont systemFontOfSize:16];
            button.tag = 100+i;
            [button sizeToFit];
            
            frame = button.frame;
            frame.size.height = self.frame.size.height;
            frame.size.width = frame.size.width + 30;
            button.frame = frame;
            frame.origin.x = CGRectGetMaxX(frame);
            
            if(i == 0){
                button.selected = YES;
                self.selectedIndex = 0;
                
                // add markline
                markLine  = [[UIView alloc]initWithFrame:CGRectMake(0, self.frame.size.height-2, 40, 2)];
                [self addSubview:markLine];
                markLine.backgroundColor = [UIColor colorFromHexString_au:@"04ab62"];
                markLine.center = CGPointMake(button.center.x, markLine.centerY);
            }
        }
        
        self.contentSize = CGSizeMake(frame.origin.x, 0);
    }else{
        return;
    }
}

-(void)setButtonSelectedAtIndex:(NSInteger)index{
    [self scrollToIndex:index];
}

-(void)scrollToIndex:(NSInteger)index{
    if(self.selectedIndex == index){
        return;
    }
    
    NSInteger a = lastIndex > self.selectedIndex ? lastIndex : self.selectedIndex;
    NSInteger b = lastIndex <= self.selectedIndex ? lastIndex : self.selectedIndex;
    
    // 忽略中间值
    if(index <= a && index >= b){
        return;
    }
    
    lastIndex = self.selectedIndex;
    UIButton * lastButton = [self viewWithTag:lastIndex + 100];
    lastButton.selected = NO;
    self.selectedIndex = index;
    lastButton = [self viewWithTag:self.selectedIndex + 100];
    lastButton.selected = YES;
    __weak typeof(self) weakself = self;
    [UIView animateWithDuration:0.2 animations:^{
        markLine.center = CGPointMake(lastButton.center.x, markLine.center.y);
    } completion:^(BOOL finished) {
        // 防止外部高频调用的时候出现中间值, 产生结果偏移
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            lastIndex = weakself.selectedIndex;
        });
    }];
    
    if(self.contentOffset.x > lastButton.frame.origin.x){
        [self setContentOffset:CGPointMake(lastButton.frame.origin.x, 0) animated:YES];
    }else if(self.contentOffset.x + self.frame.size.width < CGRectGetMaxX(lastButton.frame)){
        [self setContentOffset:CGPointMake(CGRectGetMaxX(lastButton.frame)-self.frame.size.width, 0) animated:YES];
    }
}

-(void)buttonEvent:(UIButton *)button{
    if(button.tag - 100 == self.selectedIndex && !self.repeatTouch){
        return;
    }
    NSInteger clickIndex = button.tag - 100;
    if(self.clickBlock){
        self.clickBlock(clickIndex);
    }
    
    [self scrollToIndex:clickIndex];
}

@end