Question

所以我试图使用以下代码以编程方式为我的视图添加约束。我正在尝试添加一些32的顶部空间和一些16的前导空间到一个视图，它以编程方式添加到我的一个视图控制器，但我似乎遇到了一些问题。

下面是我如何将按钮返回到我的视图的示例，以便以编程方式添加该按钮。

// Creating the button
func createDismissButton(vwParentView: OnboardingViewController) -> UIButton {

     let dismissButton = UIButton()
     dismissButton.setImage(UIImage(named: "Close"), forState: .Normal)
     dismissButton.frame =  CGRectMake(16, 32, 34, 34)
     dismissButton.addTarget(self, action: "dismiss:", forControlEvents: .TouchUpInside)

     // AUTO LAYOUT

    // WIDTH & HEIGHT
    let dismissWidthButtonConstraint = NSLayoutConstraint (item: dismissButton,
        attribute: NSLayoutAttribute.Width,
        relatedBy: NSLayoutRelation.Equal,
        toItem: nil,
        attribute: NSLayoutAttribute.NotAnAttribute,
        multiplier: 1,
        constant: 34)

    let dismissHeightButtonConstraint = NSLayoutConstraint (item: dismissButton,
        attribute: NSLayoutAttribute.Width,
        relatedBy: NSLayoutRelation.Equal,
        toItem: nil,
        attribute: NSLayoutAttribute.NotAnAttribute,
        multiplier: 1,
        constant: 34)

    // SPACING
    let dismissButtonTopConstraint = NSLayoutConstraint(item: dismissButton,
        attribute: .Top,
        relatedBy: .Equal,
        toItem: vwParentView.view,
        attribute: .Top,
        multiplier: 1.0,
        constant: 32)

    let dismissButtonLeftConstraint = NSLayoutConstraint(item: dismissButton,
        attribute: .Leading,
        relatedBy: .Equal,
        toItem: vwParentView.view,
        attribute: .Leading,
        multiplier: 1.0,
        constant: 16)


    dismissButton.addConstraint(dismissWidthButtonConstraint)
    dismissButton.addConstraint(dismissHeightButtonConstraint)

    dismissButton.addConstraint(dismissButtonTopConstraint)
    dismissButton.addConstraint(dismissButtonLeftConstraint)

     return dismissButton
}

但似乎在我添加vwParentView.view的空格上失败了，因为它在日志中引发了一个关于item属性必须是视图的错误。但是现在当我使用这些属性运行代码时，我收到以下错误。

'NSInternalInconsistencyException'，原因：'无法设置视图层次结构的布局，无法用于约束。'

我正在尝试将此按钮添加到一个视图中，该视图也是以编程方式创建的，如下所示。

override func viewWillAppear(animated: Bool) {
    // Add the view below to the current view controller
    self.view.addSubview(generatePurchasePaging().view)
}

func generatePurchasePaging() -> OnboardingViewController {

    let welcomePage = OnboardingContentViewController(title: "PAY WHAT YOU WANT", body: "I made my app so you could have the best experience reading tech related news. That’s why I want you to value it based on your satisfaction.", image: UIImage(named: "Purchase-Pig"), buttonText: "") { () -> Void in

    }

    let firstPurchasePage = OnboardingContentViewController(title: "MINT", body: "The app is great but there’s still a few places in room of improvement. If this is your feeling this is for you.", image: UIImage(named: "Purchase-Mint"), buttonText: "69p") { () -> Void in

    }

    let secondPurchasePage = OnboardingContentViewController(title: "SWEET", body: "IThis is the suggested price where you value the time I spent on development and design. Feel free to pay more or less.", image: UIImage(named: "Purchase-Lolly"), buttonText: "£1.49") { () -> Void in

    }

    let thirdPurchasePage = OnboardingContentViewController(title: "GOLD", body: "Hello is it me your looking for, if this popped into your mind using the app then this is the price for you.", image: UIImage(named: "Purchase-Coin"), buttonText: "£2.99") { () -> Void in

    }

    let purchaseVC = OnboardingViewController(backgroundImage: nil, contents: [welcomePage, firstPurchasePage, secondPurchasePage, thirdPurchasePage])
   purchaseVC.shouldMaskBackground = false

    purchaseVC.view.addSubview(createDismissButton(purchaseVC))
    return purchaseVC
}

Answer 1

一些想法：

以编程方式创建视图时，translatesAutoresizingMaskIntoConstraints默认为true。关掉它。
在将约束添加到视图层次结构之前，您是将约束设置到另一个视图（其超级视图？）。因此，请确保（a）首先执行addSubiew并且（b）应将此约束添加到最近的公共父级（通常是超级视图），而不是按钮本身。可以将.NotAnAttribute约束添加到按钮，但其余约束应添加到最近的公共父项。
您正在设置约束和frame。如果你做前者，则不需要后者。

如果您在解决上述问题后仍然无法正常工作，请分享错误的全文，而不仅仅是单行消息。

NSLayout约束失败

1 个答案: