UISegmentedControl隐藏在titleBar下面

Question

我想我错过了一些与UISegmentedControl和自动布局。

我有一个TabbedApplication (UITabBarController)，我创建了一个新的UIViewController作为选项卡。在新视图中，我添加了UISegmentedControl，并使用自动布局将其放置在顶部。

我想我不完全明白一些事情，因为UISegmentedControl隐藏在titleBar下面。你能帮我理解我错过了什么吗？谢谢你。

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import Foundation
import UIKit;

class ViewLikes:UIViewController {

override func viewDidLoad()  {
    super.viewDidLoad()
    title = "some title";


    var segmentControl:UISegmentedControl = UISegmentedControl(items:["blash", "blah blah"]);
    segmentControl.selectedSegmentIndex = 1;


    segmentControl.setTranslatesAutoresizingMaskIntoConstraints(false)
    self.view.addSubview(segmentControl)

    //Set layout
    var viewsDict = Dictionary <String, UIView>()
    viewsDict["segment"] = segmentControl;

    //controls
    self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-[segment]-|",
        options: NSLayoutFormatOptions.AlignAllCenterX,
        metrics: nil,
        views: viewsDict))

    self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|-[segment]",
        options: NSLayoutFormatOptions(0),
        metrics: nil,
        views: viewsDict))
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
}

Answer 1

您的顶部空间垂直约束必须与您的顶部布局指南，而不是您的集装箱边缘。以下代码应修复此问题：

override func viewDidLoad() {
    super.viewDidLoad()

    let segmentControl = UISegmentedControl(items:["blash", "blah blah"])
    segmentControl.selectedSegmentIndex = 1

    segmentControl.setTranslatesAutoresizingMaskIntoConstraints(false)
    self.view.addSubview(segmentControl)

    //Horizontal constraints
    view.addConstraint(NSLayoutConstraint(item: segmentControl, attribute: NSLayoutAttribute.Top, relatedBy: NSLayoutRelation.Equal, toItem: self.topLayoutGuide, attribute: NSLayoutAttribute.Bottom, multiplier: 1, constant: 10))

    //Horizontal constraints
    let viewsDict = ["segment" : segmentControl]

    self.view.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|-[segment]-|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict))
}

请注意，水平约束设置也已被重写。