ios - NSLayoutConstraint 高度不起作用

Question

我使用编程约束将 View 定义为 iOS 屏幕上的弹出窗口。

    let stopTimer = StoppageTimer(frame: CGRect.zero)

该 View 本身包含一个堆栈 View 以及几个按钮。当我尝试为我的 View 设置约束(从它的 super View - View Controller )时，除了我的 View 的高度之外，所有这些约束都被正确应用。设置这些约束的代码是(有问题的集是最后四个，就在 view.layoutIfNeeded()

func setConstraints() {
    // Remove all constraints within the UIView
    view.constraints.forEach {constraint in constraint.isActive = false}
    lblNetScore.translatesAutoresizingMaskIntoConstraints = false
    lblMatchName.translatesAutoresizingMaskIntoConstraints = false
    butUnwind.translatesAutoresizingMaskIntoConstraints = false
    butMatchStats.translatesAutoresizingMaskIntoConstraints = false
    GSButtons.translatesAutoresizingMaskIntoConstraints = false
    GAButtons.translatesAutoresizingMaskIntoConstraints = false
    sb.translatesAutoresizingMaskIntoConstraints = false
    timer.translatesAutoresizingMaskIntoConstraints = false
    butSwitch.translatesAutoresizingMaskIntoConstraints = false
    Qtr.translatesAutoresizingMaskIntoConstraints = false
    butStart.translatesAutoresizingMaskIntoConstraints = false
    stopTimer.translatesAutoresizingMaskIntoConstraints = false
    // Top Line
    NSLayoutConstraint(item: butUnwind,     attribute: .leading,  relatedBy: .equal, toItem: view, attribute: .leading,    multiplier: 1, constant:  15).isActive = true
    NSLayoutConstraint(item: butUnwind,     attribute: .top,      relatedBy: .equal, toItem: view, attribute: .topMargin,  multiplier: 1, constant:   0).isActive = true
    NSLayoutConstraint(item: lblNetScore,   attribute: .centerX,  relatedBy: .equal, toItem: view, attribute: .centerX,    multiplier: 1, constant:   0).isActive = true
    NSLayoutConstraint(item: lblNetScore,   attribute: .top,      relatedBy: .equal, toItem: view, attribute: .topMargin,  multiplier: 1, constant:   0).isActive = true
    NSLayoutConstraint(item: butMatchStats, attribute: .trailing, relatedBy: .equal, toItem: view, attribute: .trailing,   multiplier: 1, constant: -15).isActive = true
    NSLayoutConstraint(item: butMatchStats, attribute: .top,      relatedBy: .equal, toItem: view, attribute: .topMargin,  multiplier: 1, constant:   0).isActive = true
    NSLayoutConstraint(item: lblMatchName,  attribute: .top,      relatedBy: .equal, toItem: lblNetScore, attribute: .bottom,   multiplier: 1, constant: 5).isActive = true
    NSLayoutConstraint(item: lblMatchName,  attribute: .centerX,  relatedBy: .equal, toItem: view, attribute: .centerX,  multiplier: 1, constant:   0).isActive = true
    // Timer
    NSLayoutConstraint(item: timer, attribute: .top,      relatedBy: .equal, toItem: lblMatchName, attribute: .bottom,  multiplier: 1, constant: 5).isActive = true
    NSLayoutConstraint(item: timer, attribute: .centerX,  relatedBy: .equal, toItem: view,         attribute: .centerX, multiplier: 1, constant: 0).isActive = true

    NSLayoutConstraint(item: Qtr,   attribute: .top,      relatedBy: .equal, toItem: lblMatchName, attribute: .bottom,  multiplier: 1, constant: 5).isActive = true
    NSLayoutConstraint(item: Qtr, attribute: .leading,    relatedBy: .equal, toItem: view,         attribute: .leadingMargin, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: Qtr, attribute: .height,     relatedBy: .equal, toItem: timer,         attribute: .height, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: butStart,   attribute: .top, relatedBy: .equal, toItem: lblMatchName, attribute: .bottom,  multiplier: 1, constant: 5).isActive = true
    NSLayoutConstraint(item: butStart, attribute: .trailing,    relatedBy: .equal, toItem: view,   attribute: .trailingMargin, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: butStart, attribute: .height,     relatedBy: .equal, toItem: timer,   attribute: .height, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: butStart, attribute: .width,     relatedBy: .equal, toItem: nil,      attribute: .notAnAttribute, multiplier: 1, constant: 70).isActive = true


    // Switch Button
    NSLayoutConstraint(item: butSwitch, attribute: .top,      relatedBy: .equal, toItem: timer, attribute: .bottom,  multiplier: 1, constant: 5).isActive = true
    NSLayoutConstraint(item: butSwitch, attribute: .centerX,  relatedBy: .equal, toItem: view,  attribute: .centerX, multiplier: 1, constant: 0).isActive = true
    // ScoreBoard
    NSLayoutConstraint(item: sb, attribute: .top,      relatedBy: .equal, toItem: butSwitch, attribute: .bottom,  multiplier: 1, constant: 5).isActive = true
    NSLayoutConstraint(item: sb, attribute: .centerX,  relatedBy: .equal, toItem: view,      attribute: .centerX, multiplier: 1, constant: 0).isActive = true
    //Scoring buttons - GS
    NSLayoutConstraint(item: GSButtons, attribute: .top,      relatedBy: .equal, toItem: sb,   attribute: .bottom,        multiplier: 1, constant:   7).isActive = true
    NSLayoutConstraint(item: GSButtons, attribute: .height,   relatedBy: .equal, toItem: sb,   attribute: .height,        multiplier: 1, constant:  15).isActive = true
    NSLayoutConstraint(item: GSButtons, attribute: .leading,  relatedBy: .equal, toItem: view, attribute: .leadingMargin, multiplier: 1, constant:   0).isActive = true
    NSLayoutConstraint(item: GSButtons, attribute: .trailing, relatedBy: .equal, toItem: view, attribute: .trailingMargin,multiplier: 1, constant:   0).isActive = true
    // Scoring buttons - GA
    NSLayoutConstraint(item: GAButtons, attribute: .top,      relatedBy: .equal, toItem: GSButtons, attribute: .bottom,         multiplier: 1, constant:   7).isActive = true
    NSLayoutConstraint(item: GAButtons, attribute: .height,   relatedBy: .equal, toItem: sb,        attribute: .height,         multiplier: 1, constant:  15).isActive = true
    NSLayoutConstraint(item: GAButtons, attribute: .leading,  relatedBy: .equal, toItem: view,      attribute: .leadingMargin,  multiplier: 1, constant:   0).isActive = true
    NSLayoutConstraint(item: GAButtons, attribute: .trailing, relatedBy: .equal, toItem: view,      attribute: .trailingMargin, multiplier: 1, constant:   0).isActive = true
    // Stoppage Timer
    NSLayoutConstraint(item: stopTimer, attribute: .top,      relatedBy: .equal, toItem: butSwitch, attribute: .bottom,         multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: stopTimer, attribute: .height,   relatedBy: .equal, toItem: nil,       attribute: .notAnAttribute, multiplier: 1, constant: 100).isActive = true
    NSLayoutConstraint(item: stopTimer, attribute: .leading,  relatedBy: .equal, toItem: view,      attribute: .leadingMargin,  multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: stopTimer, attribute: .trailing, relatedBy: .equal, toItem: view,      attribute: .trailingMargin, multiplier: 1, constant: 0).isActive = true
    view.layoutIfNeeded()
}

因此 View 位于另一个按钮下方，并且顶部/前导/尾随约束是完美的，但高度被忽略(调试窗口中没有约束错误)。当我在调试中查看高度值时，它告诉我它为零

(lldb) po stopTimer.frame
▿ (16.0, 186.5, 343.0, 0.0)
  ▿ origin : (16.0, 186.5)
    - x : 16.0
    - y : 186.5
  ▿ size : (343.0, 0.0)
    - width : 343.0
    - height : 0.0

我使用 CGRect.zero 预先声明 View ，因为我的约束稍后会重新调整大小。

如果我将高度设置为等于另一个 View ，它可以正常工作，但它不会将其设置为恒定高度。如果我尝试以类似的方式使用宽度约束，也会发生同样的情况。

任何有关解决这个谜团的帮助将不胜感激。

编辑

当 stopTimer View 出现时(我设置 .isHidden = false)， subview 中的控件(按钮、堆栈 View 等)都显示在屏幕上，但无法访问(我无法触摸它们)，因为它们不是在 View 的范围内。抱歉冗长，但这是 stopTimer 类定义

class StoppageTimer: UIView {

lazy var StoppageType: UISegmentedControl = {
    let s = UISegmentedControl(frame: CGRect.zero)
    s.insertSegment(withTitle: "Umpire Time", at: 0, animated: false)
    s.insertSegment(withTitle: "Injury Time", at: 1, animated: false)
    s.translatesAutoresizingMaskIntoConstraints = false
    s.backgroundColor = Style.backgroundColor
    s.tintColor = Style.buttonBackgroundColorA
    return s
}()

lazy var StoppageTimer: UIStackView = {
    let s = UIStackView(frame: CGRect(x: 0, y: 0, width: 0, height: 0))
    s.axis = .horizontal
    s.distribution = .fill
    s.alignment = .fill
    s.translatesAutoresizingMaskIntoConstraints = false
    return s
}()

let bgView: UIView = {
    let v = UIView()
    v.backgroundColor = Style.labelBackgroundColorA
    v.layer.cornerRadius = CGFloat(Style.buttonCornerRadius)
    v.layer.borderWidth = 3
    v.layer.borderColor = Style.buttonBackgroundColorA.cgColor
    v.translatesAutoresizingMaskIntoConstraints = false
    return v
}()

let minutes: UILabel = {
    let l = UILabel()
    l.text = "00"
    l.textAlignment = .right
    l.backgroundColor = UIColor.clear
    l.textColor = Style.labelTextColor
    l.font = UIFont.systemFont(ofSize: 40.0, weight: .thin)
    l.translatesAutoresizingMaskIntoConstraints = false
    return l
}()

let Separator: UILabel = {
    let l = UILabel()
    l.text = ":"
    l.textAlignment = .center
    l.backgroundColor = UIColor.clear
    l.textColor = Style.labelTextColor
    l.font = UIFont.systemFont(ofSize: 40.0, weight: .ultraLight)
    l.translatesAutoresizingMaskIntoConstraints = false
    return l
}()

let seconds: UILabel = {
    let l = UILabel()
    l.text = "00"
    l.textAlignment = .left
    l.backgroundColor = UIColor.clear
    l.textColor = Style.labelTextColor
    l.font = UIFont.systemFont(ofSize: 40.0, weight: .thin)
    l.translatesAutoresizingMaskIntoConstraints = false
    return l
}()

let butCont: UIButton = {
    let b = UIButton()
    b.setTitle("Continue", for: .normal)
    b.setTitleColor(Style.buttonTextColor, for: .normal)
    b.titleLabel?.font = UIFont.systemFont(ofSize: 25)
    b.titleLabel?.adjustsFontSizeToFitWidth = true
    b.showsTouchWhenHighlighted = true
    b.translatesAutoresizingMaskIntoConstraints = false
    b.backgroundColor = Style.buttonBackgroundColorB
    b.layer.cornerRadius = CGFloat(Style.buttonCornerRadius)
    b.layer.borderWidth = CGFloat(Style.buttonBorderWidth)
    return b
}()

override init(frame: CGRect) {
    super.init(frame: frame)
    addStoppageTimer()
}

required init(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
    setStoppageTimerConstraints()
}

func addStoppageTimer() {
    StoppageTimer.arrangedSubviews.forEach { subview in subview.removeFromSuperview() }
    addSubview(bgView)
    StoppageTimer.addArrangedSubview(minutes)
    StoppageTimer.addArrangedSubview(Separator)
    StoppageTimer.addArrangedSubview(seconds)
    addSubview(StoppageTimer)
    addSubview(StoppageType)
    addSubview(butCont)
}

func setStoppageTimerConstraints() {
    constraints.forEach { constraint in constraint.isActive = false }
    translatesAutoresizingMaskIntoConstraints = false

    NSLayoutConstraint(item: bgView, attribute: .top,      relatedBy: .equal, toItem: self, attribute: .top,      multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: bgView, attribute: .bottom,   relatedBy: .equal, toItem: self, attribute: .bottom,   multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: bgView, attribute: .leading,  relatedBy: .equal, toItem: self, attribute: .leading,  multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: bgView, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1, constant: 0).isActive = true

    NSLayoutConstraint(item: StoppageType, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1, constant: 10).isActive = true
    NSLayoutConstraint(item: StoppageType, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1, constant: 20).isActive = true
    NSLayoutConstraint(item: StoppageType, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1, constant: -20).isActive = true

    NSLayoutConstraint(item: StoppageTimer, attribute: .top,      relatedBy: .equal, toItem: StoppageType, attribute: .bottom,          multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: StoppageTimer, attribute: .centerX,   relatedBy: .equal, toItem: self, attribute: .centerX, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: StoppageTimer, attribute: .width,  relatedBy: .equal, toItem: nil, attribute: .notAnAttribute,      multiplier: 1, constant: 150).isActive = true

    NSLayoutConstraint(item: butCont, attribute: .centerX, relatedBy: .equal, toItem: bgView, attribute: .centerX, multiplier: 1, constant: 0).isActive = true
    NSLayoutConstraint(item: butCont, attribute: .top, relatedBy: .equal, toItem: StoppageTimer, attribute: .bottom, multiplier: 1, constant: 5).isActive = true

    minutes.widthAnchor.constraint(equalToConstant: 60).isActive = true
    seconds.widthAnchor.constraint(equalToConstant: 60).isActive = true


    layoutIfNeeded()
}

我看不出为什么所有其他约束都能完美工作(即使高度确实是指另一个 View 的高度，而不仅仅是一个常量值)，但是当定义为常量时，高度和宽度会被忽略。调试日志完全无声，它不反对任何约束。

我还注意到，在调试时，高度约束是在执行高度约束行时设置的，但是查看 view.layoutIfNeeded() 之后的约束，高度约束不再......

(lldb) po stopTimer.constraints
▿ 1 element
  - 0 : <NSLayoutConstraint:0x6000000997d0 NetScore.StoppageTimer:0x7fc3bff223d0.height == 100   (active)>

(lldb) po stopTimer.constraints
▿ 11 elements
  - 0 : <NSLayoutConstraint:0x60c00009d6f0 V:|-(0)-[UIView:0x7fc3bff225f0]   (active, names: '|':NetScore.StoppageTimer:0x7fc3bff223d0 )>
  - 1 : <NSLayoutConstraint:0x60c000281090 UIView:0x7fc3bff225f0.bottom == NetScore.StoppageTimer:0x7fc3bff223d0.bottom   (active)>
  - 2 : <NSLayoutConstraint:0x60c0002810e0 H:|-(0)-[UIView:0x7fc3bff225f0]   (active, names: '|':NetScore.StoppageTimer:0x7fc3bff223d0 )>
  - 3 : <NSLayoutConstraint:0x60c000281130 UIView:0x7fc3bff225f0.trailing == NetScore.StoppageTimer:0x7fc3bff223d0.trailing   (active)>
  - 4 : <NSLayoutConstraint:0x60c000281180 V:|-(10)-[UISegmentedControl:0x7fc3bff23f10]   (active, names: '|':NetScore.StoppageTimer:0x7fc3bff223d0 )>
  - 5 : <NSLayoutConstraint:0x60c0002811d0 H:|-(20)-[UISegmentedControl:0x7fc3bff23f10]   (active, names: '|':NetScore.StoppageTimer:0x7fc3bff223d0 )>
  - 6 : <NSLayoutConstraint:0x60c000281220 UISegmentedControl:0x7fc3bff23f10.trailing == NetScore.StoppageTimer:0x7fc3bff223d0.trailing - 20   (active)>
  - 7 : <NSLayoutConstraint:0x60c0002812c0 V:[UISegmentedControl:0x7fc3bff23f10]-(0)-[UIStackView:0x7fc3bff23d00]   (active)>
  - 8 : <NSLayoutConstraint:0x60c000281310 UIStackView:0x7fc3bff23d00.centerX == NetScore.StoppageTimer:0x7fc3bff223d0.centerX   (active)>
  - 9 : <NSLayoutConstraint:0x60c00009f360 UIButton:0x7fc3bff23080'Continue'.centerX == UIView:0x7fc3bff225f0.centerX   (active)>
  - 10 : <NSLayoutConstraint:0x60c0002813b0 V:[UIStackView:0x7fc3bff23d00]-(5)-[UIButton:0x7fc3bff23080'Continue']   (active)>

Answer 1

在 setStoppageTimerConstraints() ，你是说:

NSLayoutConstraint(item: bgView, attribute: .top,      relatedBy: .equal, toItem: self, attribute: .top,      multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: bgView, attribute: .bottom,   relatedBy: .equal, toItem: self, attribute: .bottom,   multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: bgView, attribute: .leading,  relatedBy: .equal, toItem: self, attribute: .leading,  multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: bgView, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1, constant: 0).isActive = true

PIN bgView到所有四个侧面(因此它应该完全填充 StoppageTimer View )。

然后...

NSLayoutConstraint(item: StoppageType, attribute: .top, relatedBy: .equal, toItem: self, attribute: .top, multiplier: 1, constant: 10).isActive = true
NSLayoutConstraint(item: StoppageType, attribute: .leading, relatedBy: .equal, toItem: self, attribute: .leading, multiplier: 1, constant: 20).isActive = true
NSLayoutConstraint(item: StoppageType, attribute: .trailing, relatedBy: .equal, toItem: self, attribute: .trailing, multiplier: 1, constant: -20).isActive = true

PIN StoppageType (分段控制)前缘和后缘，并固定其 Top距离 Top 10 分 View 。

然后...

NSLayoutConstraint(item: StoppageTimer, attribute: .top,      relatedBy: .equal, toItem: StoppageType, attribute: .bottom,          multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: StoppageTimer, attribute: .centerX,   relatedBy: .equal, toItem: self, attribute: .centerX, multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: StoppageTimer, attribute: .width,  relatedBy: .equal, toItem: nil, attribute: .notAnAttribute,      multiplier: 1, constant: 150).isActive = true

PIN StoppageTimer (堆栈 View )前缘和后缘，并固定其 Top 0 分 Bottom的StoppageType .

然后...

NSLayoutConstraint(item: butCont, attribute: .centerX, relatedBy: .equal, toItem: bgView, attribute: .centerX, multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: butCont, attribute: .top, relatedBy: .equal, toItem: StoppageTimer, attribute: .bottom, multiplier: 1, constant: 5).isActive = true

PIN butCont (一个按钮)centerX，并固定其 Top距离 Bottom 5 分的StoppageTimer.

到目前为止，一切都很好。但是...您忘记添加约束来控制 Height view的本身。

所以，添加这一行:

NSLayoutConstraint(item: self, attribute: .bottom, relatedBy: .equal, toItem: butCont, attribute: .bottom, multiplier: 1.0, constant: 10.0).isActive = true

这表示view Bottom应等于 Bottom的butCont + 10 分。

现在您可以添加stopTimer到你的VC的 View 中，你只需要设置它的前导、尾随和顶部约束。 stopTimer 的内容的限制将定义其高度。

<小时/>

编辑:澄清为什么在原始代码中设置高度约束不起作用...

setConstraints()结尾在你的 VC 中，你正在这样做:

// Stoppage Timer
NSLayoutConstraint(item: stopTimer, attribute: .top,      relatedBy: .equal, toItem: butSwitch, attribute: .bottom,         multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: stopTimer, attribute: .height,   relatedBy: .equal, toItem: nil,       attribute: .notAnAttribute, multiplier: 1, constant: 100).isActive = true
NSLayoutConstraint(item: stopTimer, attribute: .leading,  relatedBy: .equal, toItem: view,      attribute: .leadingMargin,  multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: stopTimer, attribute: .trailing, relatedBy: .equal, toItem: view,      attribute: .trailingMargin, multiplier: 1, constant: 0).isActive = true

它设置顶部、前导和尾随约束和高度约束。

在您的 StoppageTimer 中查看，您实现了traitCollectionDidChange()添加/更新您的约束(它调用 setStoppageTimerConstraints() )。 setStoppageTimerConstraints()开头，您删除它的所有约束。这似乎没问题，除了......

stopTimer View 的顶部、前导和尾随约束属于您的 VC View ，而 stopTimer查看Height约束属于stopTimer.view .

traitCollectionDidChange()不止一次被调用。事实上，它在您设置高度约束之后被调用。所以:

constraints.forEach { constraint in constraint.isActive = false }

删除您刚刚从 VC 设置的高度约束。

希望这是有道理的。