如何以编程方式向 UISegmentedControl 添加约束

Question

这是我的 UISegmentedControl 代码：

   employeeSegmentedControl = UISegmentedControl(items: items)
    employeeSegmentedControl.selectedSegmentIndex = 0
    employeeSegmentedControl.backgroundColor = UIColor(red: 41/255, green: 128/255, blue: 185/255, alpha: 1.0)
    employeeSegmentedControl.tintColor = UIColor.whiteColor()
    employeeSegmentedControl.addTarget(self, action: Selector("indexChanged:"), forControlEvents: .ValueChanged)
    self.view.addSubview(employeeSegmentedControl)

    employeeSegmentedControl.setTranslatesAutoresizingMaskIntoConstraints(false)
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .Width, relatedBy: .Equal, toItem: self.view, attribute: .Width, multiplier: 1.0, constant: 0.0))
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .Height, relatedBy: .Equal, toItem: self.searchController.searchBar, attribute: .Height, multiplier: 1.0, constant: 0.0))
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .CenterX, relatedBy: .Equal, toItem: self.view, attribute: .CenterX, multiplier: 1.0, constant: 0.0))
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .CenterY, relatedBy: .Equal, toItem: self.searchController.searchBar, attribute: .CenterY, multiplier: 1.2, constant: 0.0))

如您所见，我正在向 UISegmentedControl 添加约束，但我的应用程序崩溃了。这是我的错误消息：

2015-09-03 18:50:52.241 Employee Keeper[14424:11105086] * 由于未捕获的异常而终止应用程序 'NSInvalidArgumentException'，原因：'* +[NSLayoutConstraint constraintWithItem:attribute:relatedBy:toItem:attribute:multiplier:constant:]：乘数为 0 或第二个项目为 nil 以及第一个属性的位置会创建等于常量的位置非法约束。位置属性必须成对指定' *** 首先抛出调用堆栈：

我做错了什么？

Answer 1

我想是因为你设置约束的时候你的self.searchController.searchBar是nil

如何以编程方式向 UISegmentedControl 添加约束

How do I add constraints programmatically to UISegmentedControl

ios

swift

uisegmentedcontrol