防止用户用PencilKit - Swift擦除图纸

Question

我正在使用PencilKit构建一个绘图应用程序，我有一个预装的PKDrawing，其中装载了PKCanvasView。我的目标是允许用户使用预加载的PKDrawing作为参考来玩画布。我的问题是:是否有可能使预加载的PKDraw不可擦除？请注意，我不想完全阻止橡皮擦工具，用户必须能够擦除自己的绘图，但不是参考之一。

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Answer 1

这是解决这一问题的另一种方式。这是我的工作。

让我试着举例说明一下。在这里，我只删除高亮笔和重新绘制在同一画布上的其他路径。所以看起来就像只移除荧光笔，而不是其他文本。

我在这里已经提到了你需要遵循的四个步骤

步骤1>在类中声明临时变量

var tempPKDrawing: PKDrawing?

步骤2>现在添加此PKCanvasViewDelegate方法

 // MARK: Canvas View Delegate
extension PKCanvas: PKCanvasViewDelegate {

  /// Delegate method: Note that the drawing has changed.
  public func canvasViewDrawingDidChange(_ canvasView: PKCanvasView) {
    print("canvasViewDrawingDidChange\(canvasView.drawing)")
    print ("toolPicker isVisible:\(toolPicker?.isVisible)")

//****** STEP 4> ******
    //Remove Highlighter text
    if canvasView.tool is PKEraserTool, let tempDrawing = self.tempPKDrawing {
      if canvasView.drawing.strokes.count != tempDrawing.strokes.count {
        var newDrawing : [PKStroke] = tempDrawing.strokes.filter({$0.ink.inkType != .marker})
        newDrawing += canvasView.drawing.strokes.filter({$0.ink.inkType == .marker})
        self.tempPKDrawing = nil
        self.canvasView?.drawing = PKDrawing(strokes: newDrawing)
      }
    }

  }

  public func canvasViewDidBeginUsingTool(_ canvasView: PKCanvasView) {
    print("canvasViewDidBeginUsingTool:\(canvasView.drawing)")

//****** STEP 3> ******
    if canvasView.tool is PKEraserTool {
      self.tempPKDrawing = canvasView.drawing
    }
    //canvasView.drawingPolicy = PKEraserToolReference(eraserType: .)
  }
  public func canvasViewDidEndUsingTool(_ canvasView: PKCanvasView) {
    print("canvasViewDidEndUsingTool")
  }
  public func canvasViewDidFinishRendering(_ canvasView: PKCanvasView) {
    print("canvasViewDidFinishRendering")
  }
}

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谢谢库尔;)