UIView动画在第一次尝试时没有动画

Question

我的问题是我的UIView动画仅在第一次之后才能运行.我有两套不同的动画.第一组工作正常,第二组给我带来问题.第一组将4个按钮滑动到屏幕上,比我想要的更远.(我称之为extendedState的这些位置)第二组动画将它们稍微滑回到我想要的位置.这会产生弹回正确位置的效果.

在两个动画之间还有一个短暂的秒,一旦第一组动画完成,它就会将按钮闪回到它们的起始位置.通过将起始位置设置为extendedStates(停止动画时它们将处于的位置),按钮似乎不会在动画之间移动(这很好.这就是我想要的).

这是操作的顺序:

1. 我点击一个启动第一组动画的按钮(效果非常好)
2. 在animationDidStop块中,我启动了第二组动画(这是第一次没有动画的动画)

这是按钮处理程序的代码:

@IBAction func selectAnimal(sender: UIButton) {

    showButtons()
    bigCircle.enabled = false
    enableButtons()

    if(tapToSelectLabel.hidden) {
        animator.repositionButtonsToExtendedState(buttons) //sets the starting position to the extendedState so it appears not to move between animations
        animator.slideButtonsIntoScreen(buttons, delegate: self) //this is the first set of animations

    }

    if(sender.titleLabel != nil) {

        if(bigCircleLabel.text != "Choose an animal") {

            if let answer:String = bigCircleLabel.text {
                solution = game.checkAnswer(answer, question: game.threeQuestions[game.questionIndex])
            }

            showResponse()
        }
    }
}

现在这里是animationDidStop块内的代码

let buttonRects:[CGRect] = [CGRectMake(834, 120, 175, 175),
                                        CGRectMake(631, 198, 175, 175),
                                        CGRectMake(470, 365, 175, 175),
                                        CGRectMake(386, 578, 175, 175)]

            UIView.animateWithDuration(0.35, delay: 0, options: [.BeginFromCurrentState, ], animations: {
                        self.buttons[3].frame = buttonRects[3]
                    }, completion: { (value:Bool) in
                        self.buttons[3].enabled = true

                        UIView.animateWithDuration(0.25, delay: 0, options: [ ], animations: {
                            self.buttons[2].frame = buttonRects[2]
                            }, completion: { (value:Bool) in
                                self.buttons[2].enabled = true

                                UIView.animateWithDuration(0.4, delay: 0, options: [ ], animations: {
                                    self.buttons[1].frame = buttonRects[1]
                                    }, completion: { (value:Bool) in
                                        self.buttons[1].enabled = true

                                        UIView.animateWithDuration(0.5, delay: 0, options: [ ], animations: {
                                            self.buttons[0].frame = buttonRects[0]
                                            }, completion: { (value:Bool) in
                                                self.buttons[0].enabled = true
                                        })
                                })
                        })
                    })

^此代码将按钮稍微向后滑动到我希望它们所在的位置.

这是我的动画师类的代码

animator.slideButtonsIntoScreen

func slideButtonsIntoScreen(buttons:[UIButton], delegate:UIViewController) {

    let center = CGPoint(x:delegate.view.frame.width, y:delegate.view.frame.height)
    let startAngles:[CGFloat] = [0.405, 0.75, 1.1, 1.48]
    let endAngles:[CGFloat] = [1.95, 2.25, 2.622, 2.98]
    let radii:[CGFloat] = [555, 559, 558.5, 551]
    let durations:[Double] = [1.75, 1.5, 1.25 , 1]

    for index in 0...3 {
        let path = UIBezierPath(arcCenter: center, radius: radii[index], startAngle: -startAngles[index], endAngle: -endAngles[index], clockwise: false)
        let anim = CAKeyframeAnimation(keyPath: "position")
        anim.path = path.CGPath
        anim.rotationMode = kCAAlignmentNatural
        anim.repeatCount = 0
        anim.duration = durations[index] - 0.25
        anim.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
        anim.setValue("on", forKey: "type")
        anim.delegate = delegate
        buttons[index].layer.addAnimation(anim, forKey: "animate position along path"+String(index))
        anim.removedOnCompletion = true

    }

}

animator.repositionButtonsToExtendedState

func repositionButtonsToExtendedState(buttons:[UIButton]) {


    let buttonExtendedRects:[CGRect] = [CGRectMake(755, 155, 175, 175),
                                        CGRectMake(585, 245, 175, 175),
                                        CGRectMake(450, 405, 175, 175),
                                        CGRectMake(393, 590, 175, 175)]

    for index in 0...3 {
        buttons[index].frame = buttonExtendedRects[index]
    }
}

我设置断点和打印语句,所以我知道它在第一次尝试时到达动画,它只是不显示动画.它在第一次之后每次都能正常工作.

Answer 1

使用自动布局时更改框架通常是不好的做法。从表面上看，您可以将对象设置为在完成时不重置回其原始位置，而不是将框架设置为动画停止的位置：

anim.fillMode = kCAFillModeForwards
anim.removedOnCompletion = false

但一定要在添加动画之前放置这些线

buttons[index].layer.addAnimation(anim, forKey: "animate position along path"+String(index))

为了避免在您想要向后移动按钮时再次设置帧，您应该执行基本相同的动画，而不是

clockwise: false

将其设置为 true

clockwise: true

然后从那里您可以使用结束角度作为向后运动的新开始角度，并将向后运动的结束角度设置到您需要按钮的位置