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 View Controller 。问题是:我在第二个 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 View Controller 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:

在我的主视图 Controller 中:

@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 View Controller 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
}

最佳答案

作为解决方法，我使用 UIPresentationController，它通过 topLayoutGuide.length 点移动模态视图 Controller :

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。所以我必须为这种情况硬编码一个值。

关于ios - 为什么顶部布局指南在我的 iMessage 扩展中移动，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/39070054/