Question

我正在尝试使用约束以编程方式创建UIButtons。它应该根据数组中的项创建按钮。

我将UIView出口作为viewSingle并在故事板中给出了前导，下限，尾随和高度限制。现在，当我尝试以编程方式约束UIButton时，它会给出下面提到的错误。

for (index,item) in (self.planModel.plan_settings?.sticky_buttons?.enumerated())!{

        var btnOne = UIButton()
        var btnSecond = UIButton()
        var btnThird = UIButton()

        let totalItems = self.planModel.plan_settings?.sticky_buttons?.count ?? 1

        let multiplier = (UIScreen.main.bounds.width / CGFloat(totalItems)) / UIScreen.main.bounds.width
        switch index {
        case 0:
            btnOne = UIButton(type: UIButtonType.system)
            btnOne.backgroundColor = UIColor.green
            viewSingle.addSubview(btnOne)

            btnOne.translatesAutoresizingMaskIntoConstraints = false
            NSLayoutConstraint.activate([
                btnOne.leadingAnchor.constraint(equalTo: viewSingle.leadingAnchor, constant: 0),
                btnOne.topAnchor.constraint(equalTo: viewSingle.topAnchor, constant: 0),
                // button.widthAnchor.constraint(equalTo: viewSingle!.widthAnchor, constant: 0),
                btnOne.heightAnchor.constraint(equalTo: viewSingle!.heightAnchor, constant: 0),
                btnOne.widthAnchor.constraint(equalTo: viewSingle.widthAnchor, multiplier: multiplier, constant: 0)
                ])
            self.view.layoutIfNeeded()
        case 1:
            btnSecond = UIButton(type: UIButtonType.system)
            btnSecond.backgroundColor = UIColor.yellow
            viewSingle.addSubview(btnSecond)

            btnSecond.translatesAutoresizingMaskIntoConstraints = false
            NSLayoutConstraint.activate([
                btnSecond.leadingAnchor.constraint(equalTo: btnOne.leadingAnchor, constant: 0),
                btnSecond.topAnchor.constraint(equalTo: viewSingle.topAnchor, constant: 0),
                // button.widthAnchor.constraint(equalTo: viewSingle!.widthAnchor, constant: 0),
                btnSecond.heightAnchor.constraint(equalTo: viewSingle!.heightAnchor, constant: 0),
                btnSecond.widthAnchor.constraint(equalTo: viewSingle.widthAnchor, multiplier: multiplier, constant: 0)
                ])
            self.view.layoutIfNeeded()

        case 2:
            btnThird = UIButton(type: UIButtonType.system)
            btnThird.backgroundColor = UIColor.orange
            viewSingle.addSubview(btnThird)

            btnThird.translatesAutoresizingMaskIntoConstraints = false
            NSLayoutConstraint.activate([
                btnThird.leadingAnchor.constraint(equalTo: viewSingle.leadingAnchor, constant: 0),
                btnThird.topAnchor.constraint(equalTo: viewSingle.topAnchor, constant: 0),
                // button.widthAnchor.constraint(equalTo: viewSingle!.widthAnchor, constant: 0),
                btnThird.heightAnchor.constraint(equalTo: viewSingle!.heightAnchor, constant: 0),
                btnThird.widthAnchor.constraint(equalTo: viewSingle.widthAnchor, multiplier: multiplier, constant: 0)
                ])
            self.view.layoutIfNeeded()
        default:
            break
        }


    }

错误： -

2017-12-06 19:16:03.601661 + 0530 WayOL [8637：3028327] ***由于未捕获的异常'NSGenericException'终止应用程序，原因：'无法使用锚点激活约束，因为它们没有共同的祖先。约束或其锚点是否引用不同视图层次结构中的项目？这是非法的。'

有人可以帮我解决这个问题吗？

Answer 1

您的主要问题是，您每次循环都会创建新按钮：

for (index,item) in (self.planModel.plan_settings?.sticky_buttons?.enumerated())!{

        var btnOne = UIButton()
        var btnSecond = UIButton()
        var btnThird = UIButton()

        // rest of code inside loop
}

因此，第一次循环，index等于0，并添加btnOne作为viewSingle的子视图。

下一次循环时间，您创建新 btnOne - 然后添加btnSecond到viewSingle并尝试将其约束到新 btnOne，但尚未添加到viewSingle。< / p>

如果你在外面创建了3个按钮vars - 例如你创建viewSingle的同一级别，那么从循环内部删除任何= UIButton(...)语句，你不会得到那个错误。

不确定您的整体totalItems和multiplier计算以及其他约束是否会实际执行您想要的操作。你可能需要重新思考你的方法（你还没有表明/解释你的目标，很难说）。

约束或其锚点是否引用不同视图层次结构中的项目？那是违法的

1 个答案: