PDFAnnotationWidgetSubtype签名ios

Question

我想在我的应用程序中使用PDFAnnotationWidgetSubtype签名。但它没有按预期工作。我想用Apple Pencil签名。但是下面的代码只是制作了一个给定尺寸的盒子。没有检测到铅笔/手触摸。

这是我的代码：

func addSignature() {

    let bounds = CGRect(x: 100, y: 100, width: 300, height: 50)

    let annotation = PDFAnnotation(bounds: bounds, forType: PDFAnnotationSubtype.widget, withProperties: nil)
    annotation.backgroundColor = UIColor.blue
    annotation.color = UIColor.darkGray
    annotation.fieldName = "signature"
    annotation.widgetFieldType = .signature
    annotation.shouldDisplay = true
    annotation.shouldPrint = true
    annotation.widgetControlType = .unknownControl

    let border = PDFBorder()
    border.lineWidth = 2.0
    annotation.border = border
    print("Appareance Stream \(annotation.hasAppearanceStream)")

    pdfView.document?.page(at: 0)?.addAnnotation(annotation)
}

任何帮助都将不胜感激。