ios - 为什么在模态出来的控制器上加载动画就无效呢

Question

弄了个简单地动画，就是三个点的加载动画，在普通的控制器上显示正常，但是在模态出来的控制器上就无效了，求助。。。代码如下

    CAReplicatorLayer *replicatorLayer = [CAReplicatorLayer layer];
    replicatorLayer.bounds = CGRectMake(0, 0, 80, 100);
    replicatorLayer.position = CGPointMake(CXScreenW * 0.5, CXScreenH * 0.5);
    replicatorLayer.backgroundColor = [UIColor redColor].CGColor;
    [self.layer addSublayer:replicatorLayer];
    //添加一个点
    CALayer *dotLayer = [CALayer layer];
    dotLayer.bounds = CGRectMake(0, 0, 12, 12);
    dotLayer.position = CGPointMake(15, replicatorLayer.frame.size.height/2);
    dotLayer.backgroundColor = [UIColor colorWithRed:0.1 green:0.1 blue:0.1 alpha:0.2].CGColor;
    dotLayer.cornerRadius = 7.5;
    [replicatorLayer addSublayer:dotLayer];
    //设置3个点
    replicatorLayer.instanceCount = 3;
    replicatorLayer.instanceTransform = CATransform3DMakeTranslation(replicatorLayer.frame.size.width/3, 0, 0);
    //添加动画
    CABasicAnimation *animation = [CABasicAnimation animation];
    animation.keyPath = @"transform.scale";
    animation.duration = 1.3;
    animation.fromValue = @1;
    animation.toValue = @0;
    animation.repeatCount = MAXFLOAT;
    [dotLayer addAnimation:animation forKey:nil];
    replicatorLayer.instanceDelay = 1.0/3;
    dotLayer.transform = CATransform3DMakeScale(0, 0, 0);