iOS 跑马灯(支持NSAttributedString)

跑马灯控件网上也有很多Demo，但都是传NSString类型的字符串，无法满足不同格式显示的需求，所以决定自己写一个同时支持NSString和NSAttributedString的跑马灯控件以方便自己使用。

跑马灯.gif

gif速度有点快。。。

头文件如下所示（非常简单，像平时使用UILabel一样就OK了）：

@interface SLMarqueeControl : UIView

@property (nonatomic, readonly) UILabel *marqueeLabel;

@end

核心代码：

监控app从后台进入前台时的通知（解决从后台回来时停止滚动问题）

[[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(appBecomeActive:)
                                                     name:UIApplicationDidBecomeActiveNotification
                                                   object:nil
 ];

利用KVO监控text变化，完成滚动过程。

[self.marqueeLabel addObserver:self
                            forKeyPath:@"text"
                               options:NSKeyValueObservingOptionNew
                               context:nil
 ];

利用KVO监控attributedText变化，完成滚动过程。

[self.marqueeLabel addObserver:self
                            forKeyPath:@"attributedText"
                               options:NSKeyValueObservingOptionNew
                               context:nil
 ];

完成动画过程。

- (void)startAnimation {
    if (0 == CGRectGetWidth(self.bounds)
        || 0 == CGRectGetHeight(self.bounds)) {
        return;
    }
    
    [self.innerContainer.layer removeAnimationForKey:@"Marquee"];
    [self bringSubviewToFront:self.innerContainer];
    CGSize size = [self evaluateMarqueeLabelContentSize];
    
    for (UIView *view in self.innerContainer.subviews) {
        if ([view isKindOfClass:[UILabel class]]) {
            [view removeFromSuperview];
        }
    }
    
    CGRect rect = CGRectMake(0.f, 0.f, size.width + kLabelOffset, CGRectGetHeight(self.bounds));
    
    UILabel *label = [[UILabel alloc] initWithFrame:rect];
    label.backgroundColor = [UIColor clearColor];
    label.text = self.marqueeLabel.text;
    label.attributedText = self.marqueeLabel.attributedText;
    
    [self.innerContainer addSubview:label];
    
    if (size.width > CGRectGetWidth(self.bounds)) {
        CGRect nextRect = rect;
        nextRect.origin.x = size.width + kLabelOffset;
        
        UILabel *nextLabel = [[UILabel alloc] initWithFrame:nextRect];
        nextLabel.backgroundColor = [UIColor clearColor];
        nextLabel.text = self.marqueeLabel.text;
        nextLabel.attributedText = self.marqueeLabel.attributedText;
        
        [self.innerContainer addSubview:nextLabel];
        
        CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"transform.translation.x"];
        animation.keyTimes = @[@0.f, @1.f];
        animation.duration = size.width / 50.f;
        animation.values = @[@0, @(-(size.width + kLabelOffset))];
        animation.repeatCount = INT16_MAX;
        animation.timingFunction = [CAMediaTimingFunction functionWithName:@"linear"];
        [self.innerContainer.layer addAnimation:animation forKey:@"Marquee"];
    } else {
        label.frame = self.bounds;
    }
}

控件使用很简单：
NSString类型字符串

NSString *string = @"我是跑马灯，我只能不停的滚动才能体现我的价值！请注意，前方高能；呃、其实啥也没有~~~";
self.marqueeControl.marqueeLabel.text = string;

NSAttributedString类型字符串

NSMutableAttributedString *attr = [[NSMutableAttributedString alloc] initWithString:string];
 [attr addAttributes:@{NSForegroundColorAttributeName:[UIColor yellowColor]}
                  range:NSMakeRange(5, 9)];
    
 [attr addAttributes:@{NSForegroundColorAttributeName:[UIColor redColor],
                          NSFontAttributeName:[UIFont systemFontOfSize:12.f]}
                  range:NSMakeRange(18, 8)];
    
 [attr addAttributes:@{NSForegroundColorAttributeName:[UIColor greenColor]}
                  range:NSMakeRange(30, 6)];
    
 self.attrMarqueeControl.marqueeLabel.attributedText = attr;

GitHub demo: 跑马灯