视频加载动画—iOS

前言

今天跟大家分享的是抖音中或者快手中加载视频的动画

上图看成品

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.

总结

本篇的动画技巧是 缩放的 transform.scale.y 从一个点 做layer缩放 就会出现 加载效果.如果需要本文Demo，可以加iOS高级技术交流群：624212887，获取Demo,以及更多iOS学习资料

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