执行自定义分段时的不平衡呼叫

问题描述

我已经创建了一个自定义段，它是垂直段的反向版本，下面是我的执行函数：

var sourceViewController = self.sourceViewController as UIViewController!
var destinationViewController = self.destinationViewController as UIViewController!

sourceViewController.view.addSubview(destinationViewController.view)
destinationViewController.view.frame = sourceViewController.view.frame
destinationViewController.view.transform = CGAffineTransformMakeTranslation(0, -sourceViewController.view.frame.size.height)
destinationViewController.view.alpha = 1.0

UIView.animateWithDuration(0.5, delay: 0.0, options: UIViewAnimationOptions.CurveEaseOut, animations: { () -> Void in
    destinationViewController.view.transform = CGAffineTransformMakeTranslation(0, 0)
    }) { (finished: Bool) -> Void in
            destinationViewController.view.removeFromSuperview()
            sourceViewController.presentViewController(destinationViewController, animated: false, completion: nil)
    }

当我在我的应用程序中执行它时，它会起作用，动画就是我想要的，但我在控制台中看到了这样的警告：

Unbalanced calls to begin/end appearance transitions for <Custom_Segues.ViewController: 0x7a3f9950>.

我在Stack Overflow上读了很多关于这个问题的帖子，但我没有找到一个链接到我的情况，有人知道问题是什么吗？我在我的代码上尝试了很多方法，我知道问题出在最后两行，但我不知道要更改什么。

编辑/回答：

看了答案后，我找到了一个解决方案：改变视图，然后将旧的VC应用到新的视图上，并制作动画。代码是安全的，并且在动画的结尾没有旧VC的闪现。

var sourceViewController = self.sourceViewController as UIViewController!
var destinationViewController = self.destinationViewController as UIViewController!
var duplicatedSourceView: UIView = sourceViewController.view.snapshotViewAfterScreenUpdates(false) // Screenshot of the old view.

destinationViewController.view.addSubview(duplicatedSourceView) // We add a screenshot of the old view (Bottom) above the new one (Top), it looks like nothing changed.

sourceViewController.presentViewController(destinationViewController, animated: false, completion: {
    destinationViewController.view.addSubview(duplicatedSourceView) // We add the old view (Bottom) above the new one (Top), it looks like nothing changed.

    UIView.animateWithDuration(0.33, delay: 0.0, options: UIViewAnimationOptions.CurveEaseOut, animations: { () -> Void in
        duplicatedSourceView.transform = CGAffineTransformMakeTranslation(0, sourceViewController.view.frame.size.height) // We slide the old view at the bottom of the screen
            }) { (finished: Bool) -> Void in
            duplicatedSourceView.removeFromSuperview()
        }
    })
}

推荐答案

这看起来与运行循环计时有关。

destinationViewController.view.removeFromSuperview()
sourceViewController.presentViewController(destinationViewController, animated: false, completion: nil)

这两行不应在同一运行循环内执行。

destinationViewController.view.removeFromSuperview()

// Force presentViewController() into a different runloop.
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(0.001 * Double(NSEC_PER_SEC)))
dispatch_after(time, dispatch_get_main_queue()) {
    sourceViewController.presentViewController(destinationViewController, animated: false, completion: nil)
}