ios - 在 swift 中为按钮添加约束(Apple iOS 教程)

Question

我正在为苹果编程 Tutorial (章节:“向 View 添加按钮”)用于 iOS 开发。只需复制以下代码，我就会得到不同的结果:

import UIKit

@IBDesignable class RatingControl: UIStackView {

//MARK: Properties
private var ratingButtons = [UIButton]()

var rating = 0
@IBInspectable var starSize: CGSize = CGSize(width: 44.0, height: 44.0)
@IBInspectable var starCount: Int = 5

//MARK: Initialisation
override init(frame: CGRect) {
    super.init(frame: frame)
    setupButtons()
}
required init(coder: NSCoder) {
    super.init(coder: coder)
    setupButtons()
}

//MARK: Private Methods
private func setupButtons() {

        // Create the button
        let button = UIButton()
        button.backgroundColor = UIColor.red

        // Add constraints
        button.translatesAutoresizingMaskIntoConstraints = false
        button.heightAnchor.constraint(equalToConstant: starSize.height).isActive = true
        button.widthAnchor.constraint(equalToConstant: starSize.width).isActive = true

        // Setup the button action
        button.addTarget(self, action: #selector(RatingControl.ratingButtonTapped(button:)), for: .touchUpInside)

        // Add the button to the stack
        addArrangedSubview(button)

        // Add the new button to the rating button array
        ratingButtons.append(button)
}

//MARK: Button Action
func ratingButtonTapped(button: UIButton) {
    print("Button pressed 👍")
}

约束似乎不起作用。我的红色按钮与其 super 堆栈 View 的大小完全相同。它不限于 44x44。

控制台报告无法同时满足所有约束:

      2016-12-25 18:43:02.375251 FoodTracker[13644:1695258] [LayoutConstraints] Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<NSLayoutConstraint:0x600000092160 UIButton:0x7ff15f40a740.width == 44   (active)>",
    "<NSLayoutConstraint:0x608000095a90 'UISV-canvas-connection' FoodTracker.RatingControl:0x7ff15f6116c0.leading == UIButton:0x7ff15f40a740.leading   (active)>",
    "<NSLayoutConstraint:0x608000095b30 'UISV-canvas-connection' H:[UIButton:0x7ff15f40a740]-(0)-|   (active, names: '|':FoodTracker.RatingControl:0x7ff15f6116c0 )>",
    "<NSLayoutConstraint:0x608000095630 'UIView-Encapsulated-Layout-Width' FoodTracker.RatingControl:0x7ff15f6116c0.width == 200   (active)>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x600000092160 UIButton:0x7ff15f40a740.width == 44   (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2016-12-25 18:43:02.376266 FoodTracker[13644:1695258] [LayoutConstraints] Unable to simultaneously satisfy constraints.
    Probably at least one of the constraints in the following list is one you don't want. 
    Try this: 
        (1) look at each constraint and try to figure out which you don't expect; 
        (2) find the code that added the unwanted constraint or constraints and fix it. 
(
    "<NSLayoutConstraint:0x600000091e90 UIButton:0x7ff15f40a740.height == 44   (active)>",
    "<NSLayoutConstraint:0x608000095b80 'UISV-canvas-connection' FoodTracker.RatingControl:0x7ff15f6116c0.top == UIButton:0x7ff15f40a740.top   (active)>",
    "<NSLayoutConstraint:0x608000095c70 'UISV-canvas-connection' V:[UIButton:0x7ff15f40a740]-(0)-|   (active, names: '|':FoodTracker.RatingControl:0x7ff15f6116c0 )>",
    "<NSLayoutConstraint:0x608000095680 'UIView-Encapsulated-Layout-Height' FoodTracker.RatingControl:0x7ff15f6116c0.height == 110   (active)>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x600000091e90 UIButton:0x7ff15f40a740.height == 44   (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

但是，除了上面类中的那些之外，我还没有为堆栈 View 定义其他约束。同样在 Interface Builder 中，大纲中的堆栈 View 没有额外的约束。 “UISV-canvas-connection”来自哪里？

Answer 1

在使用 Apple 的教程时发现了同样的问题，并且确实在垂直堆栈 View 之外创建了水平堆栈 View 。

将它拖回 Vertical Stack View 后，它对我有用:)