横向 UIStackView 拉伸子视图

Question

我有以下游乐场，无法弄清楚为什么 ImageView 宽度约束没有得到遵守，它填充了 StackView

上剩余的 space

import UIKit
import PlaygroundSupport

let view = UIView(frame: CGRect(x: 0, y: 0, width: 500, height: 800))

let imageView = UIView(frame: CGRect.zero)
imageView.backgroundColor = UIColor.red

imageView.translatesAutoresizingMaskIntoConstraints = false
imageView.heightAnchor.constraint(equalToConstant: 40).isActive = true
imageView.widthAnchor.constraint(equalToConstant: 40).isActive = true

let navBarHeaderStackView = UIStackView()
navBarHeaderStackView.distribution = .equalCentering
navBarHeaderStackView.alignment = .center
navBarHeaderStackView.axis = .horizontal
navBarHeaderStackView.addArrangedSubview(imageView)
//navBarHeaderStackView.addArrangedSubview(titlesStackView)

view.addSubview(navBarHeaderStackView)
navBarHeaderStackView.translatesAutoresizingMaskIntoConstraints = false

navBarHeaderStackView.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 50).isActive = true
navBarHeaderStackView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 8).isActive = true
navBarHeaderStackView.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
navBarHeaderStackView.heightAnchor.constraint(equalToConstant: 60).isActive = true

navBarHeaderStackView.backgroundColor = UIColor.blue

PlaygroundPage.current.liveView = view

Answer 1

因为这个限制

navBarHeaderStackView.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: 8).isActive = true

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Answer 2

将 trailingAnchor 设置为 lessThanOrEqualTo 而不是 equalTo。

navBarHeaderStackView.trailingAnchor.constraint(lessThanOrEqualTo: view.trailingAnchor, constant: 8).isActive = true