ios - 如何在触发新动画时取消以前的动画？

Question

我正在编写相机应用，但在用户点击屏幕时无法显示对焦框。

我的代码是(快速):

self.focusView.center = sender.locationInView(self.cameraWrapper)
self.focusView.transform = CGAffineTransformMakeScale(2, 2)
self.focusView.hidden = false

UIView.animateWithDuration(0.5, animations: { [unowned self] () -> Void in
    self.focusView.transform = CGAffineTransformIdentity
}, completion: { (finished) -> Void in
    UIView.animateWithDuration(0.5, delay: 1.0, options: nil, animations: { () -> Void in
        self.focusView.alpha = 0.0
    }, completion: { (finished) -> Void in
            self.focusView.hidden = true
            self.focusView.alpha = 1.0
    })
})

但是，如果在上一个动画未完成时连续点击屏幕，新旧动画会混淆，焦点 View 会表现得很奇怪，例如它会很快消失。

谁能告诉我如何取消之前的动画，尤其是之前的完成 block ？

Answer 1

你可以使用方法removeAllAnimations来停止动画
将您的代码替换为以下

self.focusView.center = sender.locationInView(self.cameraWrapper)
self.focusView.transform = CGAffineTransformMakeScale(2, 2)
self.focusView.hidden = false
self.focusView.layer.removeAllAnimations() // <<====  Solution
UIView.animateWithDuration(0.5, animations: { [unowned self] () -> Void in
    self.focusView.transform = CGAffineTransformIdentity
}, completion: { (finished) -> Void in

    UIView.animateWithDuration(0.5, delay: 1.0, options: nil, animations: { () -> Void in
        self.focusView.alpha = 0.0
    }, completion: { (finished) -> Void in
            self.focusView.hidden = true
            self.focusView.alpha = 1.0
    })
})

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