ios - 约束或其 anchor 是否引用不同 View 层次结构中的项目？那是违法的

Question

我正在尝试以编程方式创建带有约束的 UIButton。它应该根据数组中的项目创建按钮。

我已将 UIView socket 作为 viewSingle 并在 Storyboard 中给出了前导、底部、尾随和高度约束。现在，当我试图以编程方式约束 UIButton 时，它给出了下面提到的错误。

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] *** Terminating app due to uncaught exception 'NSGenericException', reason: 'Unable to activate constraint with anchors and because they have no common ancestor. Does the constraint or its anchors reference items in different view hierarchies? That's illegal.'

谁能帮我解决这个问题？

Answer 1

您的主要问题是每次循环都在创建NEW 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，第一次通过循环时，index 等于 0，并且您将 btnOne 添加为 viewSingle 的 subview 。

通过循环的下一次，您创建一个新 btnOne -- 然后添加btnSecond 到 viewSingle 并尝试将其限制为 new btnOne，它还没有已添加到 viewSingle。

如果您在循环外部创建了 3 个按钮变量 - 例如在您创建 viewSingle 的相同级别，则删除任何 = UIButton(... ) 循环内的语句，你不会得到那个错误。

不确定您的整体 totalItems 和 multiplier 计算以及您的其余约束是否真的会按照您的要求进行。您可能需要重新考虑您的方法(您还没有展示/解释您要做什么，所以很难说)。