IU大法
效果
实际项目中很常见的效果，如下：
效果.gif
思路
让label的宽度自适应内容，然后放到一个背景view上，背景view的clipsToBounds开启。持续的改变label的frame，当label末端的x坐标为0时，调整其首端x坐标。如下，不停的执行这段代码：
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/** 刷新跑马灯label的位置 */- (void)refreshMarqueeLabelFrame { _marqueeLabel.maxX -= 0.3; if (_marqueeLabel.maxX <= 0) { _marqueeLabel.x = self.width - 41 - 38; }}代码
代码没亮点，关键是思路
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@implementation CQMarqueeView{ UILabel *_marqueeLabel; /** 控制跑马灯的timer */ NSTimer *_timer;}#pragma mark - 构造方法- (instancetype)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // UI搭建 [self setUpUI]; } return self;}#pragma mark - UI搭建/** UI搭建 */- (void)setUpUI { self.backgroundColor = [UIColor colorWithHexString:@"fff4d8"]; //------- 左边的喇叭 -------// UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(13, 9, 16, 12)]; [self addSubview:imageView]; imageView.image = [UIImage imageNamed:@"volume-marquee"]; //------- 右边的关闭按钮 -------// UIButton *closeButton = [[UIButton alloc] initWithFrame:CGRectMake(self.width - 33, 0, 30, 30)]; [self addSubview:closeButton]; [closeButton setImage:[UIImage imageNamed:@"close-marquee"] forState:UIControlStateNormal]; [closeButton setImageEdgeInsets:UIEdgeInsetsMake(9, 9, 9, 9)]; [closeButton addTarget:self action:@selector(closeButtonClicked:) forControlEvents:UIControlEventTouchUpInside]; //------- marquee View -------// // 背景 UIView *marqueeBgView = [[UIView alloc] initWithFrame:CGRectMake(41, 0, self.width - 41 - 38, self.height)]; [self addSubview:marqueeBgView]; marqueeBgView.clipsToBounds = YES; // marquee label _marqueeLabel = [[UILabel alloc] initWithFrame:marqueeBgView.bounds]; [marqueeBgView addSubview:_marqueeLabel]; _marqueeLabel.textColor = [UIColor colorWithHexString:@"ff6666"]; _marqueeLabel.font = [UIFont systemFontOfSize:13];}#pragma mark - 关闭按钮点击/** 关闭按钮点击 */- (void)closeButtonClicked:(UIButton *)sender { if (_timer) { [_timer invalidate]; _timer = nil; } if ([self.delegate respondsToSelector:@selector(marqueeView:closeButtonDidClick:)]) { [self.delegate marqueeView:self closeButtonDidClick:sender]; }}#pragma mark - 赋值跑马灯文字/** 赋值跑马灯文字 */- (void)setMarqueeText:(NSString *)marqueeText { _marqueeText = marqueeText; _marqueeLabel.text = _marqueeText; [_marqueeLabel sizeToFit]; _marqueeLabel.centerY = self.height / 2; if (_timer) { [_timer invalidate]; _timer = nil; } // 从最右边开始跑 _marqueeLabel.x = self.width - 41 - 38; _timer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:@selector(refreshMarqueeLabelFrame) userInfo:nil repeats:YES]; [[NSRunLoop currentRunLoop] addTimer:_timer forMode:NSRunLoopCommonModes];}/** 刷新跑马灯label的位置 */- (void)refreshMarqueeLabelFrame { _marqueeLabel.x -= 0.3; if (_marqueeLabel.maxX <= 0) { _marqueeLabel.x = self.width - 41 - 38; }}注意
timer的频率设置高点，步伐设置低点，可以让动画更连贯。不过貌似timer的interval最低只能设置为0.01s。
demo
上面演示的demo
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