NSLayoutconstraints 没有按预期工作

Question

以下代码未按预期运行。 InfoLabel 未添加到视图中。我按照 viewDidLoad 中提到的顺序调用以下方法。任何快速 help/insights 都会很棒。谢谢！注意：我已经在 viewcontroller 中声明了所有变量，并且在调用相应的设置块之前不设置任何属性。

       
        self.view.addSubview(cancelButton)
        cancelButton.translatesAutoresizingMaskIntoConstraints = false
        cancelButton.addTarget(self, action: #selector(cancelButtonClicked(_:)), for: .touchUpInside)
        let constraints = [
            cancelButton.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor),
            cancelButton.widthAnchor.constraint(equalToConstant: 40),
            cancelButton.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor),
            cancelButton.heightAnchor.constraint(equalToConstant: 40)
        ]
        NSLayoutConstraint.activate(constraints)
        print(cancelButton.frame)
    }
    
    private func saveButtonSetup(){
        
        self.view.addSubview(saveButton)
        saveButton.translatesAutoresizingMaskIntoConstraints = false
        saveButton.addTarget(self, action: #selector(saveButtonClicked(_:)), for: .touchUpInside)
        let constraints = [
            saveButton.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor),
            saveButton.widthAnchor.constraint(equalToConstant: 40),
            saveButton.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor),
            saveButton.heightAnchor.constraint(equalToConstant: 40)
        ]
        NSLayoutConstraint.activate(constraints)
        print(saveButton.frame)
    }
    
    private func TitleLabelSetup(){
       TitleLabel.backgroundColor = UIManager.Colors.cellBGColor
        TitleLabel.textAlignment = .center
        TitleLabel.font = UIManager.Fonts.titleFont
       TitleLabel.textColor = UIManager.Colors.titleColor
        self.view.addSubview(TitleLabel)
        let constraints = [
            TitleLabel.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor/*self.cancelButton.trailingAnchor*/,constant: 0),
           TitleLabel.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor/*self.saveButton.leadingAnchor*/, constant: 0),
            TitleLabel.topAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.topAnchor),
            TitleLabel.heightAnchor.constraint(equalToConstant: 40)
        ]
        NSLayoutConstraint.activate(constraints)
        print(TitleLabel.frame)
    }
    
    private funcInfoLabelSetup(){
        self.view.addSubview(InfoLabel)
        let constraints = [
            InfoLabel.leadingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor,constant: 0),
           InfoLabel.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.leadingAnchor, constant: 0),
            InfoLabel.topAnchor.constraint(equalTo: TitleLabel.bottomAnchor,constant: 1),
            Label.heightAnchor.constraint(equalToConstant: 40)
        ]
        NSLayoutConstraint.activate(constraints)
        print(InfoLabel,InfoLabel.frame)
    }
    
    }```

Answer 1

translatesAutoresizingMaskIntoConstraints 没有为您的 closureInfoLabel 和 closeRequestTitleLabel 设置为 false。

Answer 2

你的约束是错误的。您将 leadingAnchor 锚定到 view 的 trailingAnchor 并将 trailingAnchor 锚定到 view 的 leadingAnchor。你还需要设置 translatesAutoresizingMaskIntoConstraints 到 false

更正如下：

private func closureInfoLabelSetup(){
    self.view.addSubview(closureInfoLabel)
    closureInfoLabel.translatesAutoresizingMaskIntoConstraints = false
    let constraints = [
        closureInfoLabel.leadingAnchor.constraint(equalTo: self.view.leadingAnchor,constant: 0),
        closureInfoLabel.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: 0),
        closureInfoLabel.topAnchor.constraint(equalTo: closeRequestTitleLabel.bottomAnchor,constant: 1),
        closureInfoLabel.heightAnchor.constraint(equalToConstant: 40)
    ]
    NSLayoutConstraint.activate(constraints)
    print(closureInfoLabel,closureInfoLabel.frame)
}

NSLayoutconstraints 没有按预期工作

NSLayoutconstraints not working as expected

ios

swift

iphone

frame

nslayoutconstraint