使用前面的UIlabel创建alpha UIView

// 创建UILabel实例
let label = UILabel(frame: CGRect(x: 0, y: 0, width: 100, height: 50))
label.text = "Hello World"
label.font = UIFont.systemFont(ofSize: 20)
label.textColor = UIColor.black

// 创建UIView实例
let view = UIView(frame: CGRect(x: 50, y: 50, width: 100, height: 50))
view.backgroundColor = UIColor.red

// 将UILabel实例添加到UIView实例中
view.addSubview(label)

// 设置UIView的alpha值
view.alpha = 0.5