Question

我不知道如何在不使用计时器概念的情况下停止此调用。今天，当我试图描述项目时，我发现这个分配内存每次都会因为以下功能而增加：

func startAnimation(index: Int) {
    UIView.animate(withDuration: 4.0, delay: 0.5, options:[UIViewAnimationOptions.allowUserInteraction, UIViewAnimationOptions.curveEaseInOut], animations: {
        self.view.backgroundColor = self.colors[index]
    }) { (finished) in
        var currentIndex = index + 1
        if currentIndex == self.colors.count { currentIndex = 0 }
        self.startAnimation(index: currentIndex)
    }
}

Answer 1

做一件简单的事，提一个标志，

最初它应该，

var isViewDissappear = false

然后，

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

        isViewDissappear = true
    }

然后在再次拨打电话时检查该标志，

func startAnimation(index: Int) {
        UIView.animate(withDuration: 4.0, delay: 0.5, options:[UIViewAnimationOptions.allowUserInteraction, UIViewAnimationOptions.curveEaseInOut], animations: {
            self.view.backgroundColor = self.colors[index]
        }) { (finished) in
            var currentIndex = index + 1
            if currentIndex == self.colors.count { currentIndex = 0 }
            if !self.isViewDissappear {
                self.startAnimation(index: currentIndex)
            }
        }
    }

就是这样。

Answer 2

您通过捕获对动画闭包的self的强引用来创建保留周期。这意味着您的self由闭包拥有，而闭包由self拥有 - 这会导致您提到的泄漏（内存使用量增加）。您可以通过使用捕获列表捕获弱对self的引用来打破周期（阅读docs）。试试这个：

func startAnimation(index: Int) {
        UIView.animate(withDuration: 4.0, delay: 0.5, options:[UIViewAnimationOptions.allowUserInteraction, UIViewAnimationOptions.curveEaseInOut], animations: { [weak self]
        self?.view.backgroundColor = self?.colors[index]
    }) { (finished) in
        var currentIndex = index + 1
        if currentIndex == self?.colors.count { currentIndex = 0 }
        self?.startAnimation(index: currentIndex)
    }
}

如何在转到另一个viewcontroller时停止后台调用？

2 个答案: