Xcode Swift - 返回视图后继续动画答案

【问题标题】：Xcode Swift - continuing animation after returning to viewXcode Swift - 返回视图后继续动画
【发布时间】：2017-05-16 02:06:48
【问题描述】：

标题可能有点含糊，所以我会直截了当。在我的 Xcode 项目中，我在初始 ViewController 中实现了一个简单的动画，它运行良好，但是在离开初始视图并移动到另一个场景，然后返回初始视图后，动画无法重新启动，我可以'不知道为什么。

这是我最初认为的相关代码

     override func viewDidAppear(_ animated: Bool) {
     super.viewDidAppear(animated)

        //cloud animation
        let oldCenter = cloud.center
        let newCenter = CGPoint(x: oldCenter.x - 800, y: oldCenter.y)
        UIView.animate(withDuration: 30.0, delay: 0.0, options:
            [.curveLinear, .repeat], animations: {
                self.cloud.center = newCenter
        }, completion: nil)
        //second cloud animation
        let oldCenter2 = cloud2.center
        let newCenter2 = CGPoint(x: oldCenter2.x + 800, y: oldCenter2.y)
        UIView.animate(withDuration: 15.0, delay: 0.0, options:
            [.curveLinear, .repeat], animations: {
                self.cloud2.center = newCenter2
        }, completion: nil)

    }

    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
    }

【问题讨论】：

标签： ios swift xcode animation swift3

【解决方案1】：

您应该将云的位置重置为它们在viewDidDisappear 中的原始中心：

var originalCenter: CGPoint!
var originalCenter2: CGPoint!

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    originalCenter = cloud.center
    originalCenter2 = cloud2.center
    ...
}

override func viewDidDisappear(_ animated: Bool) {
    super.viewDidDisappear(animated)
    // restore positions
    cloud.center = originalCenter
    cloud2.center = originalCenter2
}

【讨论】：