获取子视图高度以估计另一个视图高度

Question

你好，我想获取子视图的高度来估计 detailUIView heightAnchor。在 detailUIView 中，我有 4 个使用自动约束（以编程方式）布局的标签，我想获得视图高度，以便我可以估计 detailUIView.In 函数 estimateCardHeight 我正在迭代所有子视图并尝试获取每个子视图的高度并添加它们，但我得到 0.0。我想不通的是什么。

class ComicDetailViewController: UIViewController {
    var comicNumber = Int()
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.navigationItem.title = "Comic Number: \(comicNumber)"
    }
    let detailUIView = DetailComicUIView()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        // Do any additional setup after loading the view.
        detailUIView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(detailUIView)
        addConstraints()
        print(estimateCardHeight())
    }
   
    public func configure(with viewModel: XKCDTableViewCellVM){
        detailUIView.configure(with: viewModel)
        comicNumber = viewModel.number
        
        
    }
    private func estimateCardHeight() -> CGFloat{
        var allHeight : CGFloat = 0
        for view in detailUIView.subviews{
            allHeight += view.frame.origin.y
        }
       return allHeight
    }
 
    
    private func addConstraints(){
        var constraints = [NSLayoutConstraint]()
        constraints.append(detailUIView.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor, constant: 10))
        constraints.append(detailUIView.leftAnchor.constraint(equalTo: self.view.leftAnchor, constant: 20))
        constraints.append(detailUIView.rightAnchor.constraint(equalTo: self.view.rightAnchor, constant: -20))

        constraints.append(detailUIView.heightAnchor.constraint(equalToConstant: self.view.frame.height/3))
        
        NSLayoutConstraint.activate(constraints)
    }

    

}

Answer 1

你不见了view.layoutIfNeeded()

    addConstraints()
    view.layoutIfNeeded()
    print(estimateCardHeight())

作为apple's saying

Use this method to force the view to update its layout immediately. When using Auto Layout, the layout engine updates the position of views as needed to satisfy changes in constraints.

Lays out the subviews immediately, if layout updates are pending.

我猜：

估算身高的方法，

   private func estimateCardHeight() -> CGFloat{
        var allHeight : CGFloat = 0
        for view in detailUIView.subviews{
            allHeight += view.frame.size.height
            // allHeight += view.frame.origin.y
        }
       return allHeight
    }

Answer 2

另一种实现方式。

 override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    print(estimateCardHeight())
}

viewDidLayoutSubviews()

Called to notify the view controller that its view has just laid out its subviews.

获取子视图高度以估计另一个视图高度

getting subview height to estimate another view height

uiview

ios

swift