UISegmentedControl 隐藏在 titleBar 下

Question

我想我在 UISegmentedControl 和自动布局方面遗漏了一些东西。

i have a TabbedApplication (UITabBarController), and i created a new UIViewController to act as tab. 在新视图中我添加了 UISegmentedControl，并使用自动布局将其置于顶部。

我想我不完全理解一些东西， 导致 UISegmentedControl 隐藏在 titleBar 下 .你能帮我理解我错过了什么吗？ 谢谢。

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顶部布局指南相关，而不是与容器边距相关。下面的代码应该可以解决这个问题：

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，水平约束设置也已重写。