代码创建的UIView背景色不生效？布局间距也不符合预期

我尝试通过代码创建并加载一个包含两个UILabel的UIView（helpLabelView），预期该View与下方的pwLabel保持50pt的间距，但模拟器显示的间距明显更小。为了查看该View的实际占用区域，我为其设置了棕色背景色，却发现背景色并未生效。

截图显示：两个带背景色的UILabel（青色、绿色）直接出现在pwLabel上方，中间没有明显的50pt间距，且看不到棕色的容器背景。

容器View初始化代码 #

private let helpLabelView: UIView = {
        let container = UIView()
        let label1 = UILabel(frame: CGRect(x: 0, y: 0, width: 300, height: 20))
        label1.text = "비밀번호를 설정해주세요."
        label1.font = UIFont(name: "Pretendard-Regular", size: 15)
        label1.backgroundColor = .cyan
        
        let label2 = UILabel(frame: CGRect(x: 0, y: 20, width: 300, height: 20))
        label2.text = "(영어 대소문자, 숫자, 특수문자 각 1개 이상 사용)"
        label2.font = UIFont(name: "Pretendard-Regular", size: 15)
        label2.backgroundColor = .green
        
        container.addSubview(label1)
        container.addSubview(label2)
        
        container.backgroundColor = .brown // 此行未生效
        
        return container
    }()

容器View添加与约束设置 #

view.addSubview(helpLabelView)
helpLabelView.translatesAutoresizingMaskIntoConstraints = false

相关约束代码 #

pwLabel.bottomAnchor.constraint(equalTo: pwField.topAnchor, constant: -11),
pwLabel.leftAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leftAnchor, constant: 20),
helpLabelView.bottomAnchor.constraint(equalTo: pwLabel.topAnchor, constant: -50),
helpLabelView.leftAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leftAnchor, constant: 20),

注：pwLabel是helpLabelView下方的相邻标签，所有约束已激活

问题原因 #

1. 容器背景不显示：你给容器View设置了translatesAutoresizingMaskIntoConstraints = false，但内部子视图用frame布局，没有给容器添加尺寸约束，也没让子视图和容器建立约束关联。这导致容器View被压缩成0x0的尺寸，棕色背景自然看不到，两个子Label实际是“溢出”在容器外部显示的。
2. 间距不符合预期：因为容器尺寸为0，你设置的helpLabelView.bottomAnchor指向的是容器的底部（也就是0高度的边缘），而子Label的位置是基于frame的，所以实际显示的是子Label底部到pwLabel的距离，并非你预期的容器底部到pwLabel的50pt间距。

解决方案 #

把容器内部的子视图改成Auto Layout布局，让容器根据子视图尺寸自动调整自身大小：

方案1：手动添加Auto Layout约束

private let helpLabelView: UIView = {
        let container = UIView()
        container.backgroundColor = .brown
        
        let label1 = UILabel()
        label1.text = "비밀번호를 설정해주세요."
        label1.font = UIFont(name: "Pretendard-Regular", size: 15)
        label1.backgroundColor = .cyan
        label1.translatesAutoresizingMaskIntoConstraints = false
        
        let label2 = UILabel()
        label2.text = "(영어 대소문자, 숫자, 특수문자 각 1개 이상 사용)"
        label2.font = UIFont(name: "Pretendard-Regular", size: 15)
        label2.backgroundColor = .green
        label2.translatesAutoresizingMaskIntoConstraints = false
        
        container.addSubview(label1)
        container.addSubview(label2)
        
        NSLayoutConstraint.activate([
            // label1与容器的约束
            label1.topAnchor.constraint(equalTo: container.topAnchor),
            label1.leadingAnchor.constraint(equalTo: container.leadingAnchor),
            label1.trailingAnchor.constraint(equalTo: container.trailingAnchor),
            label1.heightAnchor.constraint(equalToConstant: 20),
            
            // label2与label1、容器的约束
            label2.topAnchor.constraint(equalTo: label1.bottomAnchor),
            label2.leadingAnchor.constraint(equalTo: container.leadingAnchor),
            label2.trailingAnchor.constraint(equalTo: container.trailingAnchor),
            label2.heightAnchor.constraint(equalToConstant: 20),
            label2.bottomAnchor.constraint(equalTo: container.bottomAnchor)
        ])
        
        return container
    }()

方案2：使用UIStackView简化布局

private let helpLabelView: UIView = {
        let container = UIView()
        container.backgroundColor = .brown
        
        let stackView = UIStackView()
        stackView.axis = .vertical
        stackView.spacing = 0 // 可根据需求调整两个Label的间距
        stackView.translatesAutoresizingMaskIntoConstraints = false
        
        let label1 = UILabel()
        label1.text = "비밀번호를 설정해주세요."
        label1.font = UIFont(name: "Pretendard-Regular", size: 15)
        label1.backgroundColor = .cyan
        label1.heightAnchor.constraint(equalToConstant: 20).isActive = true
        
        let label2 = UILabel()
        label2.text = "(영어 대소문자, 숫자, 특수문자 각 1개 이상 사용)"
        label2.font = UIFont(name: "Pretendard-Regular", size: 15)
        label2.backgroundColor = .green
        label2.heightAnchor.constraint(equalToConstant: 20).isActive = true
        
        stackView.addArrangedSubview(label1)
        stackView.addArrangedSubview(label2)
        container.addSubview(stackView)
        
        NSLayoutConstraint.activate([
            stackView.topAnchor.constraint(equalTo: container.topAnchor),
            stackView.leadingAnchor.constraint(equalTo: container.leadingAnchor),
            stackView.trailingAnchor.constraint(equalTo: container.trailingAnchor),
            stackView.bottomAnchor.constraint(equalTo: container.bottomAnchor)
        ])
        
        return container
    }()

修改后：

• 容器View会根据子视图的尺寸自动计算自身大小，棕色背景正常显示；
• helpLabelView.bottomAnchor指向容器实际底部，此时设置的-50pt间距会是容器底部到pwLabel顶部的距离，符合预期。

内容的提问来源于stack exchange，提问作者Suee97