ios - UIStoryboardSegue:顶 View 不向下滑动

我有以下快速代码，而我想实现的目标是从顶部滑出。我希望secondVCView在firstVCView下面，并且要让firstVCView滑出显示secondVCView。

当前没有动画，它只是闪烁到secondVCView。

非常感谢

import UIKit

class TopToBottomSegue: UIStoryboardSegue {

override func perform() {

    // Assign the source and destination views to local variables.
    var firstVCView = self.sourceViewController.view as UIView!
    var secondVCView = self.destinationViewController.view as UIView!

    // Get the screen width and height.
    let screenWidth = UIScreen.mainScreen().bounds.size.width
    let screenHeight = UIScreen.mainScreen().bounds.size.height

    // Specify the initial position of the destination view.
    secondVCView.frame = CGRectMake(0, 0, screenWidth, screenHeight)

    // Access the app's key window and insert the destination view below the current (source) one.
    let window = UIApplication.sharedApplication().keyWindow
    window?.insertSubview(secondVCView, belowSubview: firstVCView)

    // Animate the transition.
    UIView.animateWithDuration(0.4, animations: { () -> Void in

        firstVCView.frame = CGRectOffset(firstVCView.frame, 0.0, screenHeight)
        //secondVCView.frame = CGRectOffset(secondVCView.frame, -screenWidth, 0.0)

        }) { (Finished) -> Void in
            self.sourceViewController.presentViewController(self.destinationViewController as! UIViewController,
                animated: false,
                completion: nil)
    }

  }
}

最佳答案

据我所知，您需要在animateWithduration块内调用layoutIfNeeded以获得平滑的动画。
问候