ios - UIView.mask 设置颜色

Question

我有一个 50 像素的正方形 UIView，我将其设置为我的 super View 的掩码。

let squareView = UIView(frame...)

self.view.mask = squareView

结果是一个 50px 的正方形透明区域，但它周围的 mask 区域的颜色始终是白色。如何将透明方 block 周围的 mask 区域的颜色更改为黑色？

 _______________
|               |    
|    <-------------- Masked area that I would like to change the color of
|               |
|      000000   |
|      000000 <-------- squareView: becomes transparent as expected
|      000000   |
|      000000   |
|               |
|               |
|               |
|_______________|

Answer 1

我认为这是演示您想要的效果的代码片段。您应该能够将它作为 Xcode 模板创建的 View Controller 的 viewDidLoad() 方法粘贴到新的“单一 View ”iOS 项目中。

我需要一些方法来设置 mask View 的内容而不创建 UIView 的子类(因为我很懒)所以我的示例创建了一个图像(其 alpha channel 最多为 1.0部分带有 100x100 平方的透明 Alpha channel )。我将其设置为 mask View 的内容。

最后的计时器只是循环显示外部 View 的一堆颜色，因为......这很有趣。

override func viewDidLoad() {
      super.viewDidLoad()
      self.view.backgroundColor = UIColor.blue

      let overallView = UIView(frame: CGRect(x:100, y:100, width:300, height:300))
      overallView.backgroundColor = UIColor.green

      // Draw a graphics with a mostly solid alpha channel
      // and a square of "clear" alpha in there.
      UIGraphicsBeginImageContext(overallView.bounds.size)
      let cgContext = UIGraphicsGetCurrentContext()
      cgContext?.setFillColor(UIColor.white.cgColor)
      cgContext?.fill(overallView.bounds)
      cgContext?.clear(CGRect(x:100, y:100, width: 100, height: 100))
      let maskImage = UIGraphicsGetImageFromCurrentImageContext()
      UIGraphicsEndImageContext()

      // Set the content of the mask view so that it uses our
      // alpha channel image
      let maskView = UIView(frame: overallView.bounds)
      maskView.layer.contents = maskImage?.cgImage
      overallView.mask = maskView

      self.view.addSubview(overallView)

      var hue = CGFloat(0)
      Timer.scheduledTimer(withTimeInterval: 0.2, repeats: true) {
          (_) in
          let color = UIColor(hue: hue, saturation: 1.0, brightness: 1.0, alpha: 1.0)
          hue = hue + (1.0/20);
          if hue >= 1.0 { hue = 0 }

          overallView.backgroundColor = color
      }
  }