UIScrollView中Label文本超出屏幕时无法滚动及布局异常问题求助

你遇到的异常由三个核心配置错误导致：

1. UIScrollView的Auto Layout约束规则配置错误，contentView高度被固定，无法被内容撑开
2. 手动硬编码了contentSize，关闭了Auto Layout自动计算contentSize的能力
3. 尾部约束值为正导致控件超出屏幕边界，且imageView抗压缩优先级过低，内容过长时会被系统优先压缩

修复步骤 #

1. 修正基础配置 #

删掉手动设置scrollView.contentSize = view.frame.size的代码，调整imageView的抗压缩优先级，避免被文本控件挤掉：

// 原有配置保留，新增以下代码
// 调高imageView垂直方向抗压缩优先级，避免被压缩
imageView.setContentCompressionResistancePriority(.defaultHigh, for: .vertical)
// 可选：如果需要图片按比例展示，可增加宽高比约束，示例为3:2比例
imageView.widthAnchor.constraint(equalTo: imageView.heightAnchor, multiplier: 3/2).isActive = true
// 可选：如果需要限制图片最大高度，可增加以下约束
imageView.heightAnchor.constraint(lessThanOrEqualToConstant: UIScreen.main.bounds.height * 0.5).isActive = true

2. 修正scrollView和contentView约束 #

UIScrollView的contentLayoutGuide用于计算contentSize，frameLayoutGuide对应scrollView的可视区域，按以下规则配置即可实现自动计算滚动范围：

private func layoutScrollView() {
  scrollView.pin(toSuperviewSafeArea: .top, .trailing, .bottom, .leading)
  // contentView绑定scrollView内容区域的四个边，作为contentSize的计算依据
  contentView.pin(to: scrollView.contentLayoutGuide, edges: [.top, .trailing, .bottom, .leading])
  // contentView宽度和scrollView可视宽度保持一致，避免横向滚动
  contentView.widthAnchor.constraint(equalTo: scrollView.frameLayoutGuide.widthAnchor).isActive = true
}

3. 修正子控件约束的尾部常量 #

向父视图右、下方向的约束常量必须为负值，否则会超出父视图边界：

private func layoutImageView() {
  imageView.pin(.top, to: .top, of: contentView, constant: Spacings.margin)
  imageView.pin(.leading, to: .leading, of: contentView, constant: Spacings.margin)
  imageView.pin(.trailing, to: .trailing, of: contentView, constant: -Spacings.margin)
}

private func layoutNameLabel() {
  nameLabel.pin(.top,
                to: .bottom,
                of: imageView,
                constant: Spacings.margin)
  nameLabel.pin(.leading,
                to: .leading,
                of: contentView,
                constant: Spacings.margin)
  nameLabel.pin(.trailing,
                to: .trailing,
                of: contentView,
                constant: -Spacings.margin)
}

private func layoutDescriptionTextView() {
  descriptionLabel.pin(.top,
                       to: .bottom,
                       of: nameLabel,
                       constant: Spacings.CharacterDetailsView.descriptionBottomMargin)
  descriptionLabel.pin(.leading,
                       to: .leading,
                       of: contentView,
                       constant: Spacings.margin)
  descriptionLabel.pin(.trailing,
                       to: .trailing,
                       of: contentView,
                       constant: -Spacings.margin)
  descriptionLabel.pin(.bottom,
                       to: .bottom,
                       of: contentView,
                       constant: -Spacings.margin)
}

内容的提问来源于stack exchange，提问作者Wazza