MKMarkerAnnotationView标题未在MKSnapShot图像上绘制

Question

我试图在带有标题的图像（MKSnapshot）上绘制标记，但标题没有显示。
有谁知道为什么会出现这种情况？

let annotation = MKPointAnnotation()
    annotation.coordinate = location
    annotation.title = "TitleTest"
let pinView = MKMarkerAnnotationView(annotation: annotation, reuseIdentifier: "test")
    pinView.titleVisibility = MKFeatureVisibility.visible
    pinView.dragState = .none
    pinView.animatesWhenAdded = false
    pinView.canShowCallout = false
    pinView.titleVisibility = .visible
    pinView.contentMode = .scaleAspectFit
    pinView.bounds = CGRect(x: 0, y: 0, width: 40, height: 40)
    if rect!.contains(point) {
        let pinCenterOffset = pinView.centerOffset
        point.x -= pinView.bounds.size.width / 2
        point.y -= pinView.bounds.size.height / 2
        point.x += pinCenterOffset.x
        point.y += pinCenterOffset.y
    }
    pinView.drawHierarchy(in: CGRect(
            x:point.x,
            y:point.y,
            width:pinView.bounds.width,
            height:pinView.bounds.height),
        afterScreenUpdates: true)
    print("Draw a marker on iOS 11")

这是带有标记的UIImageView的屏幕截图，但没有标题：

Answer 1

标题可以在引脚位置下方的快照上绘制：

• 确定注释在图像坐标系中的位置snapshot.point(for: annotation.coordinate)

• 创建标题文本的属性，您可以使其与Apple使用的类似：

  private func titleAttributes() -> [NSAttributedStringKey: NSObject] {
      let paragraphStyle = NSMutableParagraphStyle()
      paragraphStyle.alignment = .center
      let titleFont = UIFont.systemFont(ofSize: 10, weight: UIFont.Weight.semibold)
      let attrs = [NSAttributedStringKey.font: titleFont,
                   NSAttributedStringKey.paragraphStyle: paragraphStyle]
      return attrs
  }
  

• 在注释的位置正下方绘制：

  private func drawTitle(title: String,
                         at point: CGPoint,
                         attributes: [NSAttributedStringKey: NSObject]) {
      let titleSize = title.size(withAttributes: attributes)
      title.draw(with: CGRect(
          x: point.x - titleSize.width / 2.0,
          y: point.y + 1,
          width: titleSize.width,
          height: titleSize.height),
                 options: .usesLineFragmentOrigin,
                 attributes: attributes,
                 context: nil)
  }
  

有关代码和屏幕截图的更完整示例，请参阅my following answer（它绘制自定义图钉图像，但此处可以使用其余代码）。