ios - 用流行创造一个无尽的动画？

Question

当使用 Coreanimation 框架时，我可以将动画设置为重复。我想将一个按钮设置为“吸引注意力”模式，这应该让他稍微长大和缩小以引起用户的注意。

我已经通过完成 block 链接了增长和收缩动画。问题是我是否以及如何从第二个动画的完成 block 开始第一个动画。

我确实收到了以下确实有道理的警告。这个问题的优雅解决方案是什么？我不喜欢为这样的事情创建计时器。

Capturing 'scaleAnimation' strongly in this block is likely to lead to a retain cycle

- (void)attractAttention:(BOOL)flag{
    _attractAttention = flag;
    float resizeValue = 1.2f;

        // Grow animation
    POPSpringAnimation *scaleAnimation = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
    scaleAnimation.fromValue  = [NSValue valueWithCGSize:CGSizeMake(1.0f, 1.0f)];
    scaleAnimation.toValue  = [NSValue valueWithCGSize:CGSizeMake(resizeValue, resizeValue)];
    scaleAnimation.completionBlock = ^(POPAnimation *anim, BOOL finished) {
            // Grow animation done
        POPSpringAnimation *scaleAnimationDown = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
        scaleAnimationDown.fromValue  = [NSValue valueWithCGSize:CGSizeMake(resizeValue, resizeValue)];
        scaleAnimationDown.toValue  = [NSValue valueWithCGSize:CGSizeMake(1.0f, 1.0f)];

        scaleAnimationDown.completionBlock = ^(POPAnimation *anim, BOOL finished) {
                // Shrink animation done
            if (_attractAttention) {
                [self.layer pop_addAnimation:scaleAnimation forKey:@"scaleUpAnimation"];
            }
        };

        [self.layer pop_addAnimation:scaleAnimationDown forKey:@"scaleDownAnimation"];
    };

    [self.layer pop_addAnimation:scaleAnimation forKey:@"scaleUpAnimation"];
}

编辑:

我还尝试创建动画的弱引用。这消除了错误，但动画不再起作用:

__weak typeof(scaleAnimation) weakAnimation = scaleAnimation;

Answer 1

您还可以使用属性 autoreveres 和 repeatCount 来获得相同的结果，而无需使用 block 。它降低了复杂性:

POPSpringAnimation *scaleAnimation = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerScaleXY];
scaleAnimation.toValue = [NSValue valueWithCGSize:CGSizeMake(0.5, 0.5)];
scaleAnimation.springBounciness = 0.f;
scaleAnimation.autoreverses = YES;
scaleAnimation.repeatCount=HUGE_VALF;
[layer pop_addAnimation:scaleAnimation forKey:@"scale"];

更好的是，如果你检查这个类https://github.com/facebook/pop/blob/master/pop/POPAnimation.h您会看到有一个 repeatForever 属性，因此您可以用它替换 repeatCount:

scaleAnimation.repeatForever=YES;