核心动画的使用

1、活动指示器

• 1.1 创建活动指示器

  @property (nonatomic, strong) UIView *activityIndicatorView;
  
  self.activityIndicatorView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 200, 200)];
  self.activityIndicatorView.backgroundColor = [UIColor redColor];
  [self.view addSubview:self.activityIndicatorView];
  
  // 创建复制图层
  CAReplicatorLayer *repLayer = [CAReplicatorLayer layer];                    // 可以把图层里面所有子层复制
  repLayer.frame = self.activityIndicatorView.bounds;
  [self.activityIndicatorView.layer addSublayer:repLayer];
  
  // 创建指示器图层
  CALayer *layer = [CALayer layer];
  layer.transform = CATransform3DMakeScale(0, 0, 0);
  layer.position = CGPointMake(self.activityIndicatorView.bounds.size.width / 2, 20);
  layer.bounds = CGRectMake(0, 0, 10, 10);
  layer.backgroundColor = [UIColor greenColor].CGColor;
  [repLayer addSublayer:layer];
  
  // 设置缩放动画
  CGFloat duration = 1.0;
  CABasicAnimation *anim = [CABasicAnimation animation];
  anim.keyPath = @"transform.scale";
  anim.fromValue = @1;
  anim.toValue = @0;
  anim.duration = duration;
  anim.repeatCount = MAXFLOAT;
  [layer addAnimation:anim forKey:nil];
  
  // 设置复制层中子层
  CGFloat count = 20;
  CGFloat angle = M_PI * 2 / count;
  repLayer.instanceCount = count;                                             // 设置复制层里面有多少个子层，包括原始层
  repLayer.instanceTransform = CATransform3DMakeRotation(angle, 0, 0, 1);     // 设置复制子层偏移量，不包括原始层，相对于原始层 x 偏移
  repLayer.instanceDelay = duration / count;                                  // 设置复制层动画延迟时间
  

• 1.2 效果