连续动画调用不起作用

Question

我有一个调用 animateWithDuration 代码的按钮，该代码淡出图像、淡出文本和新背景颜色，然后重置回正常。动画需要几秒钟才能完成并且效果很好。

不过！有问题：

有时这个按钮会在动画结束前被再次按下。当发生这种情况时，我希望当前动画停止并重新开始。

研究解决方案无效

根据我的阅读，解决方案应该很简单，只需导入 QuartzCore 并添加：

button.layer.removeAllAnimations()

这确实删除了动画，但 new/second 动画完全混乱了。应该隐藏的图像不是，文本从不显示，颜色转换都是错误的。怎么回事！？！

//Animate Finished feedback in footer bar
func animateFinished(textToDisplay: String, footerBtn: UIButton, footerImg: UIImageView) {

    //Should cancel any current animation
    footerBtn.layer.removeAllAnimations()

    footerBtn.alpha = 0
    footerBtn.setTitle(textToDisplay, forState: UIControlState.Normal)
    footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Regular", size: 18)
    footerBtn.setTitleColor(UIColor(red: 255/255.0, green: 255/255.0, blue: 255/255.0, alpha: 1.0), forState: UIControlState.Normal)
    footerBtn.backgroundColor = UIColor(red: 217/255.0, green: 217/255.0, blue: 217/255.0, alpha: 1.0)

    UIView.animateWithDuration(0.5, delay: 0.0, options: nil, animations: {
        footerImg.alpha = 0.01 //Img fades out
        footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 163/255.0, blue: 00/255.0, alpha: 0.6)
        }
        , completion: { finished in

            UIView.animateWithDuration(0.5, delay: 0.0, options: nil, animations: {
                footerBtn.alpha = 1 //Text fades in
                footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 208/255.0, blue: 11/255.0, alpha: 0.6)
                }
                , completion: { finished in

                    UIView.animateWithDuration(0.5, delay: 1.0, options: nil, animations: {
                        footerBtn.alpha = 0.01 //Text fades out
                        footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 173/255.0, blue: 00/255.0, alpha: 0.6)
                        }
                        , completion: { finished in

                            UIView.animateWithDuration(0.5, delay: 0.0, options: nil, animations: {
                                footerImg.alpha = 1 //Img fades in
                                }
                                , completion: { finished in
                                    footerBtn.backgroundColor = UIColor.clearColor()
                                    footerBtn.setTitleColor(UIColor(red: 55/255.0, green: 55/255.0, blue: 55/255.0, alpha: 1.0), forState: UIControlState.Normal)
                                    footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Light", size: 18)
                                    footerBtn.setTitle("", forState: UIControlState.Normal)
                                    footerBtn.alpha = 1
                                    //Completion blocks sets values back to norm
                            })
                    })
            })
    })
}//End of animation

@Shripada 建议我切换到关键帧以获得更具可读性的代码。下面的关键帧格式。没有解决动画中断问题。如果你能解决嵌套或关键帧格式的问题，请post吧！

func animateFinished(textToDisplay: String, footerBtn: UIButton, footerImg: UIImageView) {
    //Should cancel any current animation
    footerBtn.layer.removeAllAnimations()

    footerBtn.alpha = 0
    footerBtn.setTitle(textToDisplay, forState: UIControlState.Normal)
    footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Regular", size: 18)
    footerBtn.setTitleColor(UIColor(red: 255/255.0, green: 255/255.0, blue: 255/255.0, alpha: 1.0), forState: UIControlState.Normal)
    //footerBtn.backgroundColor = UIColor(red: 217/255.0, green: 217/255.0, blue: 217/255.0, alpha: 1.0)

    UIView.animateKeyframesWithDuration(3.0 /*Total*/, delay:0.0, options: UIViewKeyframeAnimationOptions.CalculationModeLinear, animations: {

            UIView.addKeyframeWithRelativeStartTime(0.0, relativeDuration:0.10, animations:{
                footerImg.alpha = 0.01 //Img fades out
                footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 103/255.0, blue: 00/255.0, alpha: 0.6) //Bg turns to green
            })

            UIView.addKeyframeWithRelativeStartTime(0.10, relativeDuration:0.30, animations:{
                footerBtn.alpha = 1 //Text and green bg fades in
                footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 173/255.0, blue: 11/255.0, alpha: 0.6) //BG turns greener
            })

            UIView.addKeyframeWithRelativeStartTime(0.40, relativeDuration:0.50, animations:{
                footerBtn.alpha = 0.01 //Text fades out & bg fade out
            })

        },
        completion: {  finished in
            footerImg.alpha = 1
            footerBtn.alpha = 1
            footerBtn.backgroundColor = UIColor.clearColor()
            footerBtn.setTitleColor(UIColor(red: 55/255.0, green: 55/255.0, blue: 55/255.0, alpha: 1.0), forState: UIControlState.Normal)
            footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Light", size: 18)
            footerBtn.setTitle("", forState: UIControlState.Normal)
            //Completion blocks sets values back to norm
        }
    )
}//End of 'Finished' animation

Answer 1

您应该避免使用连续动画的完成块在这种嵌套中对动画进行排序。这不仅使它非常难以阅读，而且也使它难以理解和解决您提到的问题。

有一个更好的选择，称为关键帧动画，您应该考虑使用它（可用 iOS 7 起）。

animateKeyFramesWithDuration:delay:options:animation:completion

参考documentation

你的动画代码可以使用关键帧重写（PS：我没有测试过这个，只是输入它作为你的参考）-

func animateFinished(textToDisplay: String, footerBtn: UIButton, footerImg: UIImageView) {
    //Should cancel any current animation
    footerBtn.layer.removeAllAnimations()
    footerImg.layer.removeAllAnimations()
    footerBtn.alpha = 0
    footerBtn.setTitle(textToDisplay, forState: UIControlState.Normal)
    footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Regular", size: 18)
    footerBtn.setTitleColor(UIColor(red: 255/255.0, green: 255/255.0, blue: 255/255.0, alpha: 1.0), forState: UIControlState.Normal)
    //footerBtn.backgroundColor = UIColor(red: 217/255.0, green: 217/255.0, blue: 217/255.0, alpha: 1.0)

    UIView.animateKeyframesWithDuration(3.0 /*Total*/, delay:0.0, options: UIViewKeyframeAnimationOptions.CalculationModeLinear, animations: {

            UIView.addKeyframeWithRelativeStartTime(0.0, relativeDuration:0.10, animations:{
                footerImg.alpha = 0.01 //Img fades out
                footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 103/255.0, blue: 00/255.0, alpha: 0.6) //Bg turns to green
            })

            UIView.addKeyframeWithRelativeStartTime(0.0, relativeDuration:0.30, animations:{
                footerBtn.alpha = 1 //Text and green bg fades in
                footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 173/255.0, blue: 11/255.0, alpha: 0.6) //BG turns greener
            })

            UIView.addKeyframeWithRelativeStartTime(0.0, relativeDuration:0.50, animations:{
                footerBtn.alpha = 0.01 //Text fades out & bg fade out
            })

        },
        completion: {  finished in
            footerImg.alpha = 1
            footerBtn.alpha = 1
            footerBtn.backgroundColor = UIColor.clearColor()
            footerBtn.setTitleColor(UIColor(red: 55/255.0, green: 55/255.0, blue: 55/255.0, alpha: 1.0), forState: UIControlState.Normal)
            footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Light", size: 18)
            footerBtn.setTitle("", forState: UIControlState.Normal)
            //Completion blocks sets values back to norm
        }
    )
}//End of 'Finished' animation

虽然它是 obj c，但也参考了这个 link，非常有用。 http://www.raizlabs.com/dev/2015/01/uiview-animation-sequencing-and-grouping-techniques/

Answer 2

我在您的 animateFinished 方法中添加了一些 print 行，以查看发生了什么：

func animateFinished(textToDisplay: String, footerBtn: UIButton, footerImg: UIImageView) {
    //Should cancel any current animation
    print("Remove animations")
    footerBtn.layer.removeAllAnimations()
    print("Animations removed")

    footerBtn.alpha = 0
    footerBtn.setTitle(textToDisplay, forState: UIControlState.Normal)
    footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Regular", size: 18)
    footerBtn.setTitleColor(UIColor(red: 255/255.0, green: 255/255.0, blue: 255/255.0, alpha: 1.0), forState: UIControlState.Normal)
    //footerBtn.backgroundColor = UIColor(red: 217/255.0, green: 217/255.0, blue: 217/255.0, alpha: 1.0)
    print("Initial animation setup completed")

    UIView.animateKeyframesWithDuration(3.0 /*Total*/, delay:0.0, options: UIViewKeyframeAnimationOptions.CalculationModeLinear, animations: {

            UIView.addKeyframeWithRelativeStartTime(0.0, relativeDuration:0.10, animations:{
                footerImg.alpha = 0.01 //Img fades out
                footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 103/255.0, blue: 00/255.0, alpha: 0.6) //Bg turns to green
            })

            UIView.addKeyframeWithRelativeStartTime(0.10, relativeDuration:0.30, animations:{
                footerBtn.alpha = 1 //Text and green bg fades in
                footerBtn.backgroundColor = UIColor(red: 46/255.0, green: 173/255.0, blue: 11/255.0, alpha: 0.6) //BG turns greener
            })

            UIView.addKeyframeWithRelativeStartTime(0.40, relativeDuration:0.50, animations:{
                footerBtn.alpha = 0.01 //Text fades out & bg fade out
            })

        },
        completion: {  finished in
            print("Completion block started")
            footerImg.alpha = 1
            footerBtn.alpha = 1
            footerBtn.backgroundColor = UIColor.clearColor()
            footerBtn.setTitleColor(UIColor(red: 55/255.0, green: 55/255.0, blue: 55/255.0, alpha: 1.0), forState: UIControlState.Normal)
            footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Light", size: 18)
            footerBtn.setTitle("", forState: UIControlState.Normal)
            //Completion blocks sets values back to norm
            print("Completion block finished")
        }
    )
}//End of 'Finished' animation

如果您允许动画运行完成，日志将如您所料显示：

Remove animations
Animations removed
Initial animation setup completed
Completion block started
Completion block finished

但是如果您在动画期间点击按钮，您会看到：

Remove animations
Animations removed
Initial animation setup completed
Remove animations
Animations removed
Initial animation setup completed
Completion block started
Completion block finished
Completion block started
Completion block finished

发生了什么，removeAllAnimations 导致完成块（对于第一次调用）被执行，在第二次调用的初始设置完成后，但是在之前进行第二个动画。因此，例如，在第二个动画期间按钮标题为“”。

修复相对简单：如果动画尚未完成，则不执行完成块：

        completion: {  finished in
            if (!finished) {
                return
            }
            print("Completion block started")
            footerImg.alpha = 1
            footerBtn.alpha = 1
            footerBtn.backgroundColor = UIColor.clearColor()
            footerBtn.setTitleColor(UIColor(red: 55/255.0, green: 55/255.0, blue: 55/255.0, alpha: 1.0), forState: UIControlState.Normal)
            footerBtn.titleLabel!.font = UIFont(name: "HelveticaNeue-Light", size: 18)
            footerBtn.setTitle("", forState: UIControlState.Normal)
            print("Completion block finished")
            //Completion blocks sets values back to norm
        }

此外，根据 Shripada，您需要从 footerImg 和 footerBtn 中删除动画，其中：

footerImg.layer.removeAllAnimations()

在方法的开头。

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