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自动布局设置控件位置

• AutoLayout约束:
  • 要确定一个view的约束.需要指定位置约束和尺寸约束
  • 位置约束分为: 水平方向(x) 和 垂直方向(y)

• 设置自动布局

  // MARK: - 准备UI
  private func setupUI() {
    // 添加子控件
    addSubview(iconView)
    addSubview(homeView)
    addSubview(messageLabel)
    addSubview(registerButton)
    addSubview(loginButton)
  
    // 设置布局
  
    // 使用自动约束一定要设置成false.
    iconView.translatesAutoresizingMaskIntoConstraints = false
    homeView.translatesAutoresizingMaskIntoConstraints = false
    messageLabel.translatesAutoresizingMaskIntoConstraints = false
    registerButton.translatesAutoresizingMaskIntoConstraints = false
    loginButton.translatesAutoresizingMaskIntoConstraints = false
  
    // iconView X方向
    addConstraint(NSLayoutConstraint(item: iconView, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: self, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0))
    // iconView Y方向
  
    addConstraint(NSLayoutConstraint(item: iconView, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: self, attribute: NSLayoutAttribute.centerY, multiplier: 1, constant: -40))
  
    // 房子
    // X方向
    addConstraint(NSLayoutConstraint(item: homeView, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: iconView, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0))
    // Y方向
    addConstraint(NSLayoutConstraint(item: homeView, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: iconView, attribute: NSLayoutAttribute.centerY, multiplier: 1, constant: 0))
  
    // 消息label. CenterX和iconView.CenterX重合.,宽度224
    addConstraint(NSLayoutConstraint(item: messageLabel, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: iconView, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0))
    // 顶部距离iconView底部16
    addConstraint(NSLayoutConstraint(item: messageLabel, attribute: NSLayoutAttribute.top, relatedBy: NSLayoutRelation.equal, toItem: iconView, attribute: NSLayoutAttribute.bottom, multiplier: 1, constant: 16))
    // 如果不参照其他控件toItem填nil. attribute填: NSLayoutAttribute.NotAnAttribute
    addConstraint(NSLayoutConstraint(item: messageLabel, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 224))
  
    // 注册按钮
    // 顶部距离messageLabel 16
    addConstraint(NSLayoutConstraint(item: registerButton, attribute: NSLayoutAttribute.top, relatedBy: NSLayoutRelation.equal, toItem: messageLabel, attribute: NSLayoutAttribute.bottom, multiplier: 1, constant: 16))
    // 左边和messageLabel的左边重合
    addConstraint(NSLayoutConstraint(item: registerButton, attribute: NSLayoutAttribute.left, relatedBy: NSLayoutRelation.equal, toItem: messageLabel, attribute: NSLayoutAttribute.left, multiplier: 1, constant: 0))
    // 宽度 100
    addConstraint(NSLayoutConstraint(item: registerButton, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 100))
    // 高度 35
    addConstraint(NSLayoutConstraint(item: registerButton, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 35))
  
    // 注册按钮
    // 顶部距离messageLabel 16
    addConstraint(NSLayoutConstraint(item: loginButton, attribute: NSLayoutAttribute.top, relatedBy: NSLayoutRelation.equal, toItem: registerButton, attribute: NSLayoutAttribute.top, multiplier: 1, constant: 0))
    // 左边和messageLabel的左边重合
    addConstraint(NSLayoutConstraint(item: loginButton, attribute: NSLayoutAttribute.right, relatedBy: NSLayoutRelation.equal, toItem: messageLabel, attribute: NSLayoutAttribute.right, multiplier: 1, constant: 0))
    // 宽度 100
    addConstraint(NSLayoutConstraint(item: loginButton, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: registerButton, attribute: NSLayoutAttribute.width, multiplier: 1, constant: 0))
    // 高度 35
    addConstraint(NSLayoutConstraint(item: loginButton, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: registerButton, attribute: NSLayoutAttribute.height, multiplier: 1, constant: 0))
  }
  

• 按钮图片切片