如果部分屏幕外,子ViewController安全区域插入不会更新

时间:2017-11-23 21:14:39

标签: ios iphone-x childviewcontroller safearealayoutguide

在iPhone X中横向移动子ViewController时,我遇到了安全区域的困难。

我有一个根ViewController,它的一个视图是可移动的,并包含一个嵌入的子ViewController。真正的应用程序是滑动侧边栏菜单UI。这里的示例代码是精简版本。

如果表格位于屏幕左侧,则“安全区域”布局规则将其单元格内容视图插入向右推,以允许缺口。正确。但是,如果我将子ViewController从屏幕的左边缘移开,则子项的插入不会更新以重新布局内容。

我已经意识到,如果子ViewController在其最终位置完全在屏幕上,一切都运行良好。如果它的任何部分在屏幕外,则不会发生安全区域更新。

以下是显示问题的示例代码。这适用于标准的Single View App Xcode模板项目:使用显示的代码替换ViewController文件代码。在运行时,向右滑动表格会将其从屏幕的左边缘移动到右边缘。

参见“约束(...,乘数:0.5)”行。这设置了可移动视图相对于屏幕的宽度。在0.5时,表格完全适合屏幕,安全区域在移动时更新。当向左停靠时,表格单元格面向安全区域插入,当向右停靠时,表格单元格没有额外的插入,这是正确的。

一旦乘数超过0.5,即使在0.51,当滑动右侧的部分在屏幕外时。在这种情况下,不会发生安全区域更新,因此表格单元内容插入太大 - 即使桌子左边缘现在远离安全区域,它仍然具有44像素安全区域插入。

为了使拼图更加复杂,如果它们不是UIViewController的视图,那么布局似乎在UIViews上工作正常。但我需要它与UIViewControllers一起使用。

任何人都可以解释如何让孩子ViewController尊重正确的安全区域吗?感谢。

Screen shots of the problem

重现的代码:

class ViewController: UIViewController {

    var leftEdgeConstraint : NSLayoutConstraint!
    var viewThatMoves : UIView!
    var myEmbeddedVC : UIViewController!

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = UIColor.gray

        self.viewThatMoves = UIView()
        self.viewThatMoves.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(self.viewThatMoves)

        // Relayout during animation work with multiplier = 0.5
        // With any greater value, like 0.51 (meaning part of the view is offscreen), relayout does not happen
        self.viewThatMoves.widthAnchor.constraint(equalTo: self.view.widthAnchor, multiplier: 0.5).isActive = true
        self.viewThatMoves.heightAnchor.constraint(equalTo: self.view.heightAnchor).isActive = true
        self.viewThatMoves.topAnchor.constraint(equalTo: self.view.topAnchor).isActive = true
        self.leftEdgeConstraint = self.viewThatMoves.leftAnchor.constraint(equalTo: self.view.leftAnchor, constant: 0)
        self.leftEdgeConstraint.isActive = true

        // Embed child ViewController
        self.myEmbeddedVC = MyTableViewController()

        self.addChildViewController(self.myEmbeddedVC)
        self.myEmbeddedVC.view.translatesAutoresizingMaskIntoConstraints = false
        self.viewThatMoves.addSubview(self.myEmbeddedVC.view)
        self.myEmbeddedVC.didMove(toParentViewController: self)

        // Fill containing view
        self.myEmbeddedVC.view.leftAnchor.constraint(equalTo: self.viewThatMoves.leftAnchor).isActive = true
        self.myEmbeddedVC.view.rightAnchor.constraint(equalTo: self.viewThatMoves.rightAnchor).isActive = true
        self.myEmbeddedVC.view.topAnchor.constraint(equalTo: self.viewThatMoves.topAnchor).isActive = true
        self.myEmbeddedVC.view.bottomAnchor.constraint(equalTo: self.viewThatMoves.bottomAnchor).isActive = true

        let swipeLeftRecognizer = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipe(recognizer:)))
        swipeLeftRecognizer.direction = .left
        let swipeRightRecognizer = UISwipeGestureRecognizer(target: self, action: #selector(handleSwipe(recognizer:)))
        swipeRightRecognizer.direction = .right

        self.viewThatMoves.addGestureRecognizer(swipeLeftRecognizer)
        self.viewThatMoves.addGestureRecognizer(swipeRightRecognizer)
    }

    @objc func handleSwipe(recognizer:UISwipeGestureRecognizer) {
        UIView.animate(withDuration: 1) {

            if recognizer.direction == .left {
                self.leftEdgeConstraint.constant = 0
            }
            else if recognizer.direction == .right {
                self.leftEdgeConstraint.constant = self.viewThatMoves.frame.size.width
            }

            self.view.setNeedsLayout()
            self.view.layoutIfNeeded()

            // Tried this: has no effect
            // self.myEmbeddedVC.viewSafeAreaInsetsDidChange()
        }
    }
}

class MyTableViewController: UITableViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = UIColor.blue
        self.title = "Test Table"

        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        self.navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Left", style: .plain, target: nil, action: nil)
        self.navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Right", style: .plain, target: nil, action: nil)
    }

    // MARK: - Table view data source

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 25
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = UITableViewCell(style: .default, reuseIdentifier: nil)
        cell.contentView.backgroundColor = UIColor.green
        cell.backgroundColor = UIColor.yellow
        cell.textLabel?.text = "This is row \(indexPath.row)"
        cell.textLabel?.backgroundColor = UIColor.clear

        return cell
    }
}

3 个答案:

答案 0 :(得分:1)

半相关,我希望一个包含的视图控制器始终具有与另一个视图相同的插图。就我而言,它始终是全屏显示,因此我只使用了窗口,但是这种方法适用于任何其他视图。

private final class InsetView: UIView {
    override var safeAreaInsets: UIEdgeInsets {
        window?.safeAreaInsets ?? .zero
    }
}

final class MyViewController: UIViewController {
    override func loadView() {
        view = InsetView()
    }
}

这对我来说是完美的。最初,我试图通过使附加值成为视图控制器应具有的值与实际具有的值之间的差来计算additionalSafeAreaInsets中的safeAreaInsetsDidChange,但这在滚动视图中确实很不稳定。

答案 1 :(得分:0)

我已经设法通过丑陋的方式“修复”了这个问题。在父视图控制器中,您需要执行以下操作:

- (void) viewSafeAreaInsetsDidChange {
  [super viewSafeAreaInsetsDidChange];

  // Fix for child controllers not receiving an update on safe area insets
  // when they're partially not showing
  for (UIViewController *childController in self.childViewControllers) {
    UIEdgeInsets prevInsets = childController.additionalSafeAreaInsets;
    childController.additionalSafeAreaInsets = self.view.safeAreaInsets;
    childController.additionalSafeAreaInsets = prevInsets;
  }
}

这会强制子视图控制器正确更新其safeAreaInsets。

答案 2 :(得分:-1)

它似乎是系统行为:如果子视图控制器的视图在垂直或/和水平方向上看起来不完全处于其父视图控制器的边界,则其安全区域的相应方向不会更新。 / p>

听起来,如果你希望子视图控制器超出它的父视图控制器边界,你应该使用transform属性,但是安全仍然不会完全正确,但是,它会在轮换时更新。 / p>