在横向使用iPhone X的 child ViewController上滑动时，我在使用安全区时遇到了困难。
我有一个根ViewController，其 View 之一是可移动的，并且包含一个嵌入式子ViewController。真正的应用程序是滑动的侧边栏菜单UI。这里的示例代码是简化版本。
如果表格位于屏幕的左侧，则“安全区域”布局规则会将其单元格contentView插入项推到右侧以允许出现缺口。正确的。但是，如果我将子级ViewController移离屏幕的左边缘，则子级的插图不会更新以重播内容。
我已经意识到，实际上，如果子ViewController在其最终位置完全显示在屏幕上，则一切正常。如果其中任何部分不在屏幕上，则不会发生“安全区域”更新。
这是显示此问题的示例代码。这适用于标准的Single View App Xcode模板项目:用显示的代码替换ViewController文件代码。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“constraint(...，乘数:0.5)”行。这设置了相对于屏幕的可移动 View 的宽度。值为0.5时，表格将完全适合屏幕，并且安全区域会随着移动而更新。左停靠时，表格单元格遵循“安全区域”插图，右停靠时，表格单元格中没有正确的额外插图。
一旦乘数超过0.5(甚至在0.51时)，表格的右滑动部分便不在屏幕上。在这种情况下，不会发生安全区域更新，因此表格单元格内容插入太大了-即使表格的左边缘现在不在安全区域附近，它仍然具有44像素的安全区域插入。
更令人困惑的是，如果UIViews不是UIViewController的 View ，则布局似乎可以很好地工作。但是我需要它与UIViewControllers一起使用。
谁能解释如何让子级ViewController遵守正确的安全区域？谢谢。
复制代码:
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
}
}
最佳答案
我设法用一个丑陋的技巧“解决”了这个问题。在父 View Controller 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;
}
}
这将强制 subview Controller 正确更新其safeAreaInsets。
关于ios - 如果部分离开屏幕，则子ViewController安全区域插图不会更新，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/47463341/