动画效果
实现思路：同一位置创建两个一样大小view，一个upView一个downView，其分别有一个和本身同样大小的子控件UILabel，展示相同的文字。upView在上面，红色背景色，其上面的label是白色字体，透明背景。downView在下面，透明背景色，红色边框，其上面的label是红色字体，透明背景。通过改变upView的宽度实现动画效果。
源码(源码没有进行封装,细节都没有处理,望见谅)代码如下：
- (void)viewDidLoad {
[super viewDidLoad];
/*
给upView的frame值做动画才是label能够混色显示的核心
upView(红色背景) ===> upLabel(白色底字)
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downView(白色背景) ===> downLabel(红色底字)
*/
_downView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 220, 22)];
_downView.center = self.view.center;
[self.view addSubview:_downView];
_downView.layer.cornerRadius = 2;
_downView.layer.masksToBounds = YES;
_downView.layer.borderColor = [UIColor redColor].CGColor;
_downView.layer.borderWidth = 0.5f;
_downView.backgroundColor = [UIColor whiteColor];
_downLabel = [[UILabel alloc] initWithFrame:_downView.bounds];
[_downView addSubview:_downLabel];
_downLabel.textAlignment = NSTextAlignmentCenter;
_downLabel.text = @"LeiLuRong - iOS Programmer";
_downLabel.font = [UIFont systemFontOfSize:14];
_downLabel.textColor = [UIColor redColor];
_upView = [[UIView alloc] initWithFrame:_downView.bounds];
_upView.center = self.view.center;
[self.view addSubview:_upView];
_upView.layer.cornerRadius = 2;
_upView.layer.masksToBounds = YES;
_upView.backgroundColor = [UIColor redColor];
_upLabel = [[UILabel alloc] initWithFrame:_upView.bounds];
[_upView addSubview:_upLabel];
_upLabel.textAlignment = NSTextAlignmentCenter;
_upLabel.text = _downLabel.text;
_upLabel.font = _downLabel.font;
_upLabel.textColor = [UIColor whiteColor];
_timer = [[GCDTimer alloc] initInQueue:[GCDQueue mainQueue]];
__weak typeof(self) weakSelf = self;
[_timer event:^{
[UIView animateWithDuration:0.5f delay:0.f usingSpringWithDamping:3.f initialSpringVelocity:0 options:0 animations:^{
weakSelf.upView.width = arc4random()%220;
} completion:^(BOOL finished) {
}];
} timeInterval:NSEC_PER_SEC];
[_timer start];
}
代码已经放在GitHub,里面有更多动画效果，在不断更新，欢迎下载查看，喜欢可以star.
