为 UIViewPropertyAnimator 的 fractionComplete 设置动画以模糊背景

Question

所以我使用新的 UIViewPropertyAnimator 和 UIVisualEffectView 来实现与 Spotlight 搜索相同的效果，当您在主屏幕上向下滚动时它会模糊背景。

我正在使用 fractionComplete 属性来设置平移 UIView 时模糊程度的百分比。

    animator = UIViewPropertyAnimator(duration: 1, curve: .linear) {
        self.blurEffectView.effect = nil
    }

模糊度的变化范围为 0.0 - 1.0。

        animator?.fractionComplete = blurValue

但是，当我取消平移手势时，我希望模糊从原来的位置恢复为无模糊（例如 ~ -> 1.0），持续时间约为 0.4 毫秒。

现在我只是在取消平移手势时将 fractionComplete 设置为 1.0。相反，我想为它制作动画。
我试过 UIView.animate(withDuration.. 但它不影响 UIViewPropertyAnimators fractionComplete，这是模糊 UIVisualEffectView 的唯一方法。

有什么想法吗？

Answer 1

似乎fractionComplete有一个错误（我在Whosebug上的问题：UIViewPropertyAnimator does not update the view when expected), rdar://30856746。属性只设置状态从inactive到active , 但不更新视图，因为（我假设）还有另一个内部状态不会触发。

要解决此问题，您可以这样做：

animator.startAnimation() // This will change the `state` from inactive to active
animator.pauseAnimation() // This will change `isRunning` back to false, but the `state` will remain as active

// Now any call of `fractionComplete` should update your view correctly!
animator.fractionComplete = /* your value here */

这里有一个 playground 片段可以玩：

let liveView = UIView(frame: CGRect(x: 0, y: 0, width: 400, height: 50))
liveView.backgroundColor = .white

PlaygroundPage.current.needsIndefiniteExecution = true
PlaygroundPage.current.liveView = liveView

let square = UIView(frame: CGRect(x: 0, y: 0, width: 50, height: 50))
square.backgroundColor = .red

liveView.addSubview(square)

let animator = UIViewPropertyAnimator.init(duration: 5, curve: .linear)

animator.addAnimations {

    square.frame.origin.x = 350
}

let blurView = UIVisualEffectView(effect: UIBlurEffect(style: .dark))
blurView.frame = liveView.bounds

liveView.addSubview(blurView)

animator.addAnimations {

    blurView.effect = nil
}

// If you want to restore the blur after it was animated, you have to 
// safe a reference to the effect which is manipulated
let effect = blurView.effect

animator.addCompletion {
    // In case you want to restore the blur effect
    if [=11=] == .start { blurView.effect = effect }
}

animator.startAnimation()
animator.pauseAnimation()

DispatchQueue.main.asyncAfter(deadline: .now() + 2) {

    animator.fractionComplete = 0.5
}

DispatchQueue.main.asyncAfter(deadline: .now() + 4) {

    // decide the direction you want your animation to go.
    // animator.isReversed = true
    animator.startAnimation()
}

Answer 2

如果您仍在寻找一种无需使用滑块或手势即可真正为 fractionComplete 制作动画的方法，我对使用 CADisplayLink 的结果非常满意。你可以在这里看到我的结果：https://gist.github.com/vegather/07993d15c83ffcd5182c8c27f1aa600b

Answer 3

我使用延迟循环来减少“fractionComplete”

func resetAnimator(){
        
        let duration = 1.0 / 60.0
        
        if self.animator.fractionComplete > 0 {
            self.animator.fractionComplete -= 0.06
            delay(duration, closure: {
                self.resetAnimator()
            })
        }
    }

func delay(_ delay:Double, closure:@escaping ()->()) {
        DispatchQueue.main.asyncAfter(
            deadline: DispatchTime.now() + Double(Int64(delay * Double(NSEC_PER_SEC))) / Double(NSEC_PER_SEC), execute: closure)
    }

为 UIViewPropertyAnimator 的 fractionComplete 设置动画以模糊背景

Animate the fractionComplete of UIViewPropertyAnimator for blurring the background

swift

blur

uivisualeffectview

uiviewpropertyanimator