iOS仿抖音视频加载动画效果的实现方法

@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
}

- (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;
 }
}

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