AutoLayout – 多控件自适应布局

intrinsicContentSize详解

对于UILabel, UIimageView，UIButton等控件都有intrinsicContentSize的特点

• intrinsic Content Size: 固有内部巨细，拥有此特点的控件在设置束缚时，假如没有设置控件的巨细，就会根据此特点来设置控件的巨细
  • 比方UILabel设置束缚时，只需要指定位置，就能根据文本内容和字体巨细计算出label的巨细

在水平/垂直并行布局中，两个控件的intrinsicSize（固有巨细)比父控件的宽/高的数值大，父控件就没有办法彻底展示完成，就只能经过紧缩其间一个控件来实现。假如咱们想要想要指定某个控件来进行自适应，紧缩另外一个控件，就需要修改控件的束缚优先级，以下两个方法修改优先级

• setContentCompressionResistancePriority(抗紧缩)
  • 数值越低，在宽/高度不够下，就会被紧缩
  • 常见默认值：UILayoutPriority.defaultHigh = 750

    open func setContentCompressionResistancePriority(_ priority: UILayoutPriority, for axis: NSLayoutConstraint.Axis)

• setContentHuggingPriority (抗拉伸)
  • 数组越低。在宽/高度剩余的情况下就会被拉伸
  • 常见默认值：UILayoutPriority.defaultLow = 250

    open func setContentHuggingPriority(_ priority: UILayoutPriority, for axis: NSLayoutConstraint.Axis)

使用场景:

• contentCompressionResistancePriority (抗紧缩)

      lazy var label1: UILabel = {
          let label = UILabel()
          label.text = "可能会显现省略号的label1"
          return label
      }()
      lazy var label2: UILabel = {
          let label = UILabel()
          label.text = "优先自适应的宽度的label2"
          return label
      }()
      view.addSubview(label1)
      view.addSubview(label2)
      label1.snp.makeConstraints { make in
          make.left.top.bottom.equalTo(0)
      }
      label2.snp.makeConstraints { make in
          make.right.top.bottom.equalTo(0)
          make.left.equalTo(self.label1.snp.right).offset(5)
      }
  

  • 依照上面的代码显现会label1正常显现，label2被紧缩，假如需求是确保label2正常显现,需要调用setContentCompressionResistancePriority 设置束缚优先级

      label1.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
      label2.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
  

• contentHuggingPriority(抗拉伸)

      lazy var label1: UILabel = {
          let label = UILabel()
          label.text = "label1"
          return label
       }()
      lazy var label2: UILabel = {
          let label = UILabel()
          label.text = "被拉伸的label2"
          return label
        }()
      view.addSubview(label1)
      view.addSubview(label2)
      label1.snp.makeConstraints { make in
          make.left.top.bottom.equalTo(0)
      }
      label2.snp.makeConstraints { make in
          make.right.top.bottom.equalTo(0)
          make.left.equalTo(self.label1.snp.right).offset(5)
      }
  

  • 依照上面的代码显现会label1会被拉伸，label2正常显现，假如需求是label1正常显现，拉伸label2,需要调用setContentHuggingPriority 设置束缚优先级

      label1.setContentHuggingPriority(.defaultHigh, for: .horizontal)
      label2.setContentHuggingPriority(.defaultLow, for: .horizontal)