swift - MKMarkerAnnotationView 标题未绘制在 MKSnapShot 图像上

Question

我尝试在带有标题的图像 (MKSnapshot) 上绘制标记，但标题未显示。
有谁知道为什么会出现这种情况吗？

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")

这是我的 UIImageView 的屏幕截图，带有标记，但没有标题:

Answer 1

标题可以绘制在图钉位置下方的快照上:

• 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，您可以使其类似于 Apple 使用的属性:

  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
  }
  

• 将其绘制在注释位置的正下方:

  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)
  }
  

有关包含代码和屏幕截图的更完整示例，请参阅 my following answer (它绘制了一个自定义引脚图像，但其余代码可以在此处使用)。