实现原理

首先我创建一个视图

@interface ViewController ()@property (nonatomic, strong) UIView *playLoadingView;@end@implementation ViewController- (void)viewDidLoad { [super viewDidLoad]; //init player status bar self.playLoadingView = [[UIView alloc]init]; self.playLoadingView.backgroundColor = [UIColor whiteColor]; [self.playLoadingView setHidden:YES]; [self.view addSubview:self.playLoadingView]; //make constraintes [self.playLoadingView mas_makeConstraints:^(MASConstraintMaker *make) { make.center.equalTo(self.view); make.width.mas_equalTo(1.0f); //宽 1 dp make.height.mas_equalTo(0.5f); //高 0.5 dp }]; [self startLoadingPlayAnimation:YES]; //调用动画代码}

这里我们可以看到 我们实际上创建的是一个 1pt宽度 0.5 pt的宽度 的视图

紧接着动画实现的代码

- (void)startLoadingPlayAnimation:(BOOL)isStart { if (isStart) { self.playLoadingView.backgroundColor = [UIColor whiteColor]; self.playLoadingView.hidden = NO; [self.playLoadingView.layer removeAllAnimations]; CAAnimationGroup *animationGroup = [[CAAnimationGroup alloc] init]; animationGroup.duration = 0.5; animationGroup.beginTime = CACurrentMediaTime() + 0.5; animationGroup.repeatCount = MAXFLOAT; animationGroup.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]; CABasicAnimation *scaleAnimation = [CABasicAnimation animation]; scaleAnimation.keyPath = @"transform.scale.x"; scaleAnimation.fromValue = @(1.0f); scaleAnimation.toValue = @(1.0f * ScreenWidth); CABasicAnimation *alphaAnimation = [CABasicAnimation animation]; alphaAnimation.keyPath = @"opacity"; alphaAnimation.fromValue = @(1.0f); alphaAnimation.toValue = @(0.5f); [animationGroup setAnimations:@[scaleAnimation, alphaAnimation]]; [self.playLoadingView.layer addAnimation:animationGroup forKey:nil]; } else { [self.playLoadingView.layer removeAllAnimations]; self.playLoadingView.hidden = YES; }}

完事 就这几行代码 搞定

其实核心的只有4行代码

CABasicAnimation *scaleAnimation = [CABasicAnimation animation];scaleAnimation.keyPath = @"transform.scale.x";scaleAnimation.fromValue = @(1.0f);scaleAnimation.toValue = @(1.0f * ScreenWidth);

关键在scaleAnimation.keyPath = @"transform.scale.x"; 这里我们要沿着x做缩放

缩放的得值从 1~屏幕宽度, 当然值多大自己可以控制.

如果@"transform.scale.y" 则是沿着Y轴缩放

当然 如果写成@"transform.scale" 那就X,Y 一起缩放 大家可以试试.