swift - 如何为 MKPolyline 和 MKPolygon 添加描述？

Question

如何在 Swift 和 MapKit 中向折线和多边形添加注释？按点很简单。

Answer 1

S.，

我不确定您在这里问什么，但我假设您想在折线上的某处显示注释。

首先介绍如何获取折线: 因此，假设您有一个 CLLocation 对象数组，它将在 map 上绘制折线。我们将此位置对象数组称为:myLocations，其类型为 [CLLocation]。现在，您在应用程序的某个位置调用了一个创建折线的方法，我们将此方法称为 createOverlayObject(locations: [CLLocation]) -> MKPolyline。

您的调用可能如下所示:

let overlayPolyline = createOverlayObject(myLocations)

您调用的方法可能如下所示:

func createOverlayObject(locations: [CLLocation]) -> MKPolyline {
    //This method creates the polyline overlay that you want to draw.
    var mapCoordinates = [CLLocationCoordinate2D]()

    for overlayLocation in locations {

        mapCoordinates.append(overlayLocation.coordinate)
    }

    let polyline = MKPolyline(coordinates: &mapCoordinates[0], count: mapCoordinates.count)

    return polyline
}

这是第一部分，不要忘记实现mapView(_:rendererForOverlay覆盖:)来渲染线条。这部分可能看起来像这样:

func mapView(mapView: MKMapView, rendererForOverlay overlay: MKOverlay) -> MKOverlayRenderer {
    //This function creatss the renderer for the polyline overlay. This makes the polyline actually display on screen.
    let renderer = MKPolylineRenderer(overlay: overlay)
    renderer.strokeColor = mapLineColor //The color you want your polyline to be.
    renderer.lineWidth = self.lineWidth

    return renderer
}

现在第二部分在 map 上的某个位置获取注释。如果您知道要放置注释的坐标，这实际上很简单。创建和显示注释又很简单，假设您已经定义了一个名为 myNiceMapView 的 map View :

func createAnnotation(myCoordinate: CLLocationCoordinate2D) {
    let myAnnotation = MKPointAnnotation()
    myAnnotation.title = "My nice title"
    startAnnotation.coordinate = myCoordinate

    self.myNiceMapView.addAnnotations([myAnnotation])
}

不要忘记实现mapView(_: MKMapView, viewForAnnotation注释:) -> MKAnnotationView？方法，可能如下所示:

func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
    //This is the mapview delegate method that adjusts the annotation views.

    if annotation.isKindOfClass(MKUserLocation) {

        //We don't do anything with the user location, so ignore an annotation that has to do with the user location.
        return nil
    }

    let identifier = "customPin"
    let trackAnnotation = MKAnnotationView.init(annotation: annotation, reuseIdentifier: identifier)

    trackAnnotation.canShowCallout = true

    if annotation.title! == "Some specific title" { //Display a different image
        trackAnnotation.image = UIImage(named: "StartAnnotation")
        let offsetHeight = (trackAnnotation.image?.size.height)! / 2.0
        trackAnnotation.centerOffset = CGPointMake(0, -offsetHeight)
    } else { //Display a standard image.
        trackAnnotation.image = UIImage(named: "StopAnnotation")
        let offsetHeight = (trackAnnotation.image?.size.height)! / 2.0
        trackAnnotation.centerOffset = CGPointMake(0, -offsetHeight)
    }

    return trackAnnotation
}

现在的挑战是找到放置注释的正确坐标。我找不到比你有一个 CLLocationCooperative2D 引用你想要放置注释的位置更好的东西了。然后使用 for-in 循环找到要放置注释的位置，如下所示:

for location in myLocations {

  if (location.latitude == myReferenceCoordinate.latitude) && (location.longitude == myReferenceCoordinate.longitude) {
    self.createAnnotation(location: CLLOcationCoordinate2D)
  }
}

希望这能回答您的问题。