为什么顶部布局指南在我的 iMessage 扩展中移动

Question

我有一个 iMessage 扩展程序，但我在使用顶部布局指南时遇到了一些问题。我有一个 MSMessagesAppViewController 来处理演示文稿样式之间的变化。在我的扩展程序中，我有一个按钮。单击它时，我会转换为扩展的演示样式，然后以模态方式显示视图控制器。问题是：第二个 VC 中的 UI 隐藏在顶部导航栏后面。我认为这很奇怪，因为我将约束设置为顶部布局指南。所以我仔细研究了我的代码并开始调试顶部布局指南。我注意到在我转换到扩展的演示文稿样式后，topLayoutGuide.length = 86。它应该是这样的。但是当我以模态方式呈现第二个视图控制器时，顶部布局指南重置为 0。为什么它不是 86，因为它应该是？这是我的代码：

在我的主要viewController:

@IBAction func addStickerButtonPressed(_ sender: AnyObject) {
    shouldPerformCreateSegue = true
    theSender = sender
    requestPresentationStyle(.expanded)

}    
override func didTransition(to presentationStyle: MSMessagesAppPresentationStyle) {
    if presentationStyle == .expanded {
        if shouldPerformCreateSegue == true {
            shouldPerformCreateSegue = false
            performSegue(withIdentifier: "CreateStickerSegue", sender: theSender)//here is where I present the new viewController
        } else {
            searchBar.becomeFirstResponder()
            searchBar.placeholder = nil
            searchBar.showsCancelButton = true
            searchBar.tintColor = UIColor.white
        }
    } else {
        searchBar.showsCancelButton = false
    }
    print(topLayoutGuide.length) //This prints out 86
}

在另一个模态呈现的视图控制器中：

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    self.view.addConstraint(navBar.topAnchor.constraint(equalTo: topLayoutGuide.bottomAnchor))
    print(topLayoutGuide.length) //This prints out 0
}

Answer 1

我相信这是之前 iOS 10 测试版中的已知错误。在我将 iOS 版本升级到最新版本后，我遇到了同样的问题，顶部和底部布局指南按预期工作。

Answer 2

作为解决方法，我使用 UIPresentationController，它将模态视图控制器移动 topLayoutGuide.length 点：

class MyViewController: MSMessagesAppViewController {

    private func presentModalViewController() {
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self
        imagePicker.sourceType = .savedPhotosAlbum

        imagePicker.modalPresentationStyle = .custom
        imagePicker.transitioningDelegate = self

        present(imagePicker, animated: true, completion: nil)
    }
}
// MARK: - UIViewControllerTransitioningDelegate
extension MyViewController: UIViewControllerTransitioningDelegate {

    func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
        let vc = PresentationController(presentedViewController: presented, presenting: presenting)
        // I really don't want to hardcode the value of topLayoutGuideLength here, but when the extension is in compact mode, topLayoutGuide.length returns 172.0.
        vc.topLayoutGuideLength = topLayoutGuide.length > 100 ? 86.0 : topLayoutGuide.length
        return vc
    }
}


class PresentationController: UIPresentationController {

    var topLayoutGuideLength: CGFloat = 0.0

    override var frameOfPresentedViewInContainerView: CGRect {
        guard let containerView = containerView else {
            return super.frameOfPresentedViewInContainerView
        }
        return CGRect(x: 0, y: topLayoutGuideLength, width: containerView.bounds.width, height: containerView.bounds.height - topLayoutGuideLength)
    }
}

唯一的问题是当您从紧凑模式调用 presentModalViewController 时，topLayoutGuide.length 是 172.0，原因不明。所以我不得不为这种情况硬编码一个值。

Answer 3

我使用了 Andrey 的稍微不同的版本

class MyViewController: MSMessagesAppViewController {
    private func presentModalViewController() {
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self
        imagePicker.sourceType = .savedPhotosAlbum
        imagePicker.modalPresentationStyle = .custom
        imagePicker.transitioningDelegate = self
        present(
            imagePicker,
            animated: true,
            completion: nil
        )
    }
}

extension MyViewController: UIViewControllerTransitioningDelegate {
    func presentationController(
         forPresented presented: UIViewController,
         presenting: UIViewController?,
         source: UIViewController
    ) -> UIPresentationController? {
         let vc = PresentationController(
             presentedViewController: presented,
             presenting: presenting
         )
         vc.framePresented = modalBoundaries.frame
         return vc
    }
}

class PresentationController: UIPresentationController {
     var framePresented = CGRect.zero
     override var frameOfPresentedViewInContainerView: CGRect {
         return framePresented
    }
}

modalBoundaries 是一个虚拟的 UIView 约束（在我的例子中通过 XIB）尊重任何 TopLayoutGuide 长度。

为什么顶部布局指南在我的 iMessage 扩展中移动

Why is the top layout guide moving in my iMessage extension

ios

autolayout

imessage

swift