尝试呈现视图控制器时对开始/结束外观转换的不平衡调用

Question

当我尝试呈现以前作为子控制器添加的视图控制器时，我收到Unbalanced calls to begin/end appearance transitions错误的Unbalanced calls to begin/end appearance transitions ，如何解决这个问题？

开始/结束外观过渡的不平衡调用

class VideoViewController: UIViewController {

}


class BigPlayerVC: UIViewController {
    let videoVC = VideoViewController()

    override func viewDidLoad() {
        super.viewDidLoad()
        addChild(videoVC)
        view.addSubview(videoVC.view)
        videoVC.view.translatesAutoresizingMaskIntoConstraints = false
    //  view.constrainViewEqual(videoReactController.playerView, top: 0, bottom: 0, left: 0, righta: 0)
        videoVC.didMove(toParent: self)
    }

    @objc func onBTNClick() {
        videoVC.willMove(toParent: nil)
        videoVC.view.removeFromSuperview()
        videoVC.view.translatesAutoresizingMaskIntoConstraints = true
        videoVC.removeFromParent()
        self.present(videoVC, animated: false, completion: nil)
    }
}

Answer 1

我有一个临时解决方案：只需在 DispatchBlock 中移动present方法，延迟如下：

DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.1) {
    self.present(videoVC, animated: false, completion: nil)
} 

Answer 2

我遇到了和你完全一样的问题。 您应该在videoVC收听viewDidDisappeared ，然后呈现视图控制器。 方法viewDidDisappeared会立即viewDidDisappeared ，因此您不会注意到性能问题。

   @objc func onBTNClick() {
        videoVC.willMove(toParent: nil)
        videoVC.view.removeFromSuperview()
        videoVC.removeFromParent()
        videoVC.onViewDidDisappeared = {
             [unowned self, videoVC] in
             self.present(videoVC, animated: false, completion: nil)
             videoVC.onViewDidDisappeared = nil
        }
    }

final class YourViewController: UIViewController {
    var onViewDidDisappeared: (() -> Void)? = nil

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

[编辑] 不仅去除不平衡的调用，而且去除可能出现在AppleTV上的UICollectionView不聚焦问题