作者：Chouee
原文地址

最近重构项目的通信录页面，旧版本的索引条相当丑陋，找了下轮子又找不到，没办法，只能自己造了。发现微信的通讯录索引条样式还不错，照着写了一个，顺便添加了震动效果(Impact Feedback)。

首先看一下效果：

单击索引条时

单击索引条字母

滑动tableView时

滑动tableView时.gif

在索引条上滑动时

在索引条上滑动时.gif

实现原理

主要分为以下几步：

1、每一个索引，都是一个label，把所有label都竖直排列在一个父view中。这里没有使用重用池，主要考虑到一般的索引条，字母数量也不会太多。

_labelArr = [NSMutableArray new];
for (int i = 0; i < indexes.count; i++) {
    CGFloat y = (_sectionHeight * i);

    UILabel *alphaLabel = [[UILabel alloc] initWithFrame:CGRectMake(x, y, width, height)];
    alphaLabel.textAlignment = NSTextAlignmentCenter;
    alphaLabel.text = [[indexes objectAtIndex:i] uppercaseString];
    alphaLabel.font = [UIFont boldSystemFontOfSize:10.0];
    alphaLabel.backgroundColor = [UIColor clearColor];
    alphaLabel.textColor = self.textColor;
    alphaLabel.layer.cornerRadius = width * 0.5;
    alphaLabel.clipsToBounds = YES;
    [self addSubview:alphaLabel];
    [_labelArr addObject:alphaLabel];
}

2、当在父view中触摸时，通过touchMoved等方法处理触摸点和索引label之间的关系，如果触摸点落在label范围之内，则将label高亮选中。

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesMoved:touches withEvent:event];

    CGPoint touchPoint = [[[event touchesForView:self] anyObject] locationInView:self];
    [self toSelectTitle:touchPoint];
}

// 通过touchPoint找到对应的索引label
- (void)toSelectTitle:(CGPoint)touchPoint
{
    if(touchPoint.x <= 0 ||
       touchPoint.y <= 0 ||
       touchPoint.x >= self.bounds.size.width ||
       touchPoint.y >= self.bounds.size.height) return;
    __block NSString *title;
    __block NSInteger index = 0;

    [_labelArr enumerateObjectsUsingBlock:^(__kindof UILabel * _Nonnull subview, NSUInteger idx, BOOL * _Nonnull stop) {
        if(touchPoint.y < CGRectGetMaxY(subview.frame)) {
            _preLabel.backgroundColor = [UIColor clearColor];
            _preLabel.textColor = _textColor;

            subview.backgroundColor = _selectedBackgroundColor;
            subview.textColor = _selectedTextColor;
            _preLabel = subview;

            index = idx;
            title = subview.text;
            *stop = YES;
        }
    }]; 

    ......
}

3、添加震动效果，并触发点击回调

//震动
if (@available(iOS 10.0, *)) {
    UIImpactFeedbackGenerator *gen = [[UIImpactFeedbackGenerator alloc] initWithStyle:UIImpactFeedbackStyleLight];
    [gen prepare];
    [gen impactOccurred];
}

//回调
if (_delegate && [_delegate conformsToProtocol:@protocol(TTIndexBarDelegate)]) {
    [_delegate indexDidChanged:self index:index title:title];
}

如何使用

默认样式：

self.indexBar = [[TTIndexBar alloc] initWithFrame:CGRectMake(self.view.frame.size.width - 30, 0, 30, self.view.frame.size.height)];
self.indexBar.delegate = self;
[self.view addSubview:self.indexBar];

[self.indexBar setIndexes:[NSMutableArray arrayWithObjects:@"A",@"B",@"C",@"D",@"E",@"F",@"G",@"H",@"I",@"J", nil]];

自定义样式：

self.indexBar = [[TTIndexBar alloc] initWithFrame:CGRectMake(self.view.frame.size.width - 30, 0, 30, self.view.frame.size.height)];
self.indexBar.delegate = self;
[self.view addSubview:self.indexBar];   

//Custom property
self.indexBar.textColor = [UIColor redColor];
self.indexBar.selectedTextColor = [UIColor greenColor];
self.indexBar.selectedBackgroundColor = [UIColor yellowColor];
self.indexBar.detailViewDrawColor = [UIColor cyanColor];
self.indexBar.detailViewTextColor = [UIColor orangeColor];

[self.indexBar setIndexes:[NSMutableArray arrayWithObjects:@"A",@"B",@"C",@"D",@"E",@"F",@"G",@"H",@"I",@"J", nil]];

Delegate:

- (void)indexDidChanged:(TTIndexBar *)indexBar index:(NSInteger)index title:(NSString *)title;

GitHub

TTIndexBar

资料推荐

如果你正在跳槽或者正准备跳槽不妨动动小手，添加一下咱们的交流群1012951431来获取一份详细的大厂面试资料为你的跳槽多添一份保障。