(Error: Custom pin not found) when trying to fill map with markers from hardcoded locations

Question

我想用硬编码坐标填充地图，以便使用 Xamarin.Forms.Maps

显示带有自定义地图的图钉标记

我的 HardcodeLocations class 是：

public class HardcodedLocations
{
    public static List<Position> Positions = new List<Position>
    {
           new Position(41.19197,   25.33719 ),
           new Position(41.26352,   25.1471 ),
           new Position(41.26365,   25.24215 ),
           new Position(41.26369,   25.33719 ),
           new Position(41.26365,   25.43224 ),
     };
}

在构造函数中 class 我试图加载这样的标记：

public AboutPage()
{
    InitializeComponent();

    for (int i = 0; i < HardcodedLocations.Positions.Count; i++)
    {
        CustomPin pin = new CustomPin
        {
            Type = PinType.Place,
            Position = HardcodedLocations.Positions[i],
            Label = "Xamarin San Francisco Office",
            Address = "394 Pacific Ave, San Francisco CA",
            Name = "Xamarin",
            Url = "http://xamarin.com/about/"
        };
        customMap.CustomPins = new List<CustomPin> { pin };
        customMap.Pins.Add(pin);
        customMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(42.8742, 25.3187), Distance.FromMiles(1.0)));
    }
}

但我在 iOS 项目的 CustomMapRender class 中收到错误：

var customPin = GetCustomPin(annotation as MKPointAnnotation);
if (customPin == null)
{
    throw new Exception("Custom pin not found");
}

这是同一个class:

中GetViewForAnnotation方法中的所有代码

protected override MKAnnotationView GetViewForAnnotation(MKMapView mapView, IMKAnnotation annotation)
{
    MKAnnotationView annotationView = null;

    if (annotation is MKUserLocation)
        return null;

    var customPin = GetCustomPin(annotation as MKPointAnnotation);
    if (customPin == null)
    {
        throw new Exception("Custom pin not found");
    }

    annotationView = mapView.DequeueReusableAnnotation(customPin.Name);
    if (annotationView == null)
    {
        annotationView = new CustomMKAnnotationView(annotation, customPin.Name);
        annotationView.Image = UIImage.FromFile("pin.png");
        annotationView.CalloutOffset = new CGPoint(0, 0);
        annotationView.LeftCalloutAccessoryView = new UIImageView(UIImage.FromFile("monkey.png"));
        annotationView.RightCalloutAccessoryView = UIButton.FromType(UIButtonType.DetailDisclosure);
        ((CustomMKAnnotationView)annotationView).Name = customPin.Name;
        ((CustomMKAnnotationView)annotationView).Url = customPin.Url;
    }
    annotationView.CanShowCallout = true;

    return annotationView;
}

我不知道如何解决这个错误，因为当我使用基本 xamarin.forms.maps（没有自定义）时，我只是像这样填充地图：

for (int i = 0; i < HardcodedLocations.Positions.Count; i++)
{
    Pin pin = new Pin
    {
        //Label = $"{i + 1}",
        Label = $"{i + 1}",
        Address = "Кликни тук за да видиш прогнозата.",
        Type = PinType.Place,
        Position = HardcodedLocations.Positions[i]
    };

    map.Pins.Add(pin);
}

这是GetCustomPin的方法：

CustomPin GetCustomPin(MKPointAnnotation annotation)
    {
        var position = new Position(annotation.Coordinate.Latitude, annotation.Coordinate.Longitude);
        foreach (var pin in customPins)
        {
            if (pin.Position == position)
            {
                return pin;
            }
        }
        return null;
    }

这是CustomPin代码：

    public class CustomPin : Pin
{
    public string Name { get; set; }
    public string Url { get; set; }
}

要更改引脚，必须重构整个代码，在基本项目中创建 CustomMap 和 CustomPin classes 并创建 CustomMapRenderer 和 CustomMKAnnotationView class 在 iOS 和 Android 项目中。

参考：https://github.com/xamarin/xamarin-forms-samples/tree/main/CustomRenderers/Map

有没有办法清除这个错误？

=================================== 更新

在这种方法中，我尝试比较两个 Position 属性：

CustomPin GetCustomPin(MKPointAnnotation annotation)
    {

        var position = new Position(annotation.Coordinate.Latitude, annotation.Coordinate.Longitude);

        foreach (var pin in customPins)
        {
            if (pin.Position.Latitude == position.Latitude && pin.Position.Longitude == position.Longitude)
            {
                return pin;
            }
        }
        return null;
    }

但我仍然收到同样的错误 ;(

Answer 1

正如 Jason 在评论中指出的那样，您需要更改向地图添加项目的方式。

List<CustomPin> pins = new List<CustomPin>();
for (int i = 0; i < HardcodedLocations.Positions.Count; i++)
{
    CustomPin pin = new CustomPin
    {
        Type = PinType.Place,
        Position = HardcodedLocations.Positions[i],
        Label = "Xamarin San Francisco Office",
        Address = "394 Pacific Ave, San Francisco CA",
        Name = "Xamarin",
        Url = "http://xamarin.com/about/"
    };
    
    customMap.Pins.Add(pin);
}

customMap.CustomPins = pins;
customMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(42.8742, 25.3187), Distance.FromMiles(1.0)));

您在循环的每次迭代中都用一个包含单个项目的新列表覆盖了 CustomPins。

(Error: Custom pin not found) when trying to fill map with markers from hardcoded locations

(Error: Custom pin not found) when trying to fill map with markers from hardcoded locations

c#

xamarin.forms

xamarin.forms.maps

=================================== 更新