c# - 如何修复.Exception：'未找到特定引脚的自定义引脚

问题描述

请帮我解决这个问题。 我正在使用这篇文章在 xamarin 中制作自定义渲染器： Xamarin Form Custom Renderer

一切正常，直到我将 pin 信息转换为 JSON 文件。

所以基本上现在LAT、LNG、标签、名称和 URL 都存储在JSON 文件而不是 C# 文件中。为了测试，我做了 3 个临时别针。但其中只有 1 个显示自定义呈现的窗口。当我单击其他 2 个引脚时，会发生异常，因为未找到自定义引脚。但是为最后一个引脚找到了自定义引脚，但不是第一个和第二个引脚，这让我感到困惑。

我的代码：

JSON文件：

[

{"Label"   :"Country1",
        "Address":"A multine paragraph",
        "Lat":"-12",
        "Lng":"14",
        "Name":"Xamarin",
         "Url": "http://xamarin.com/about/"
},


{ "Label"  :"Country2",
         "Address":"Multiline paragraph",
         "Lat":"-25", 
         "Lng":"45",
         "Name":"Xamarin",
         "Url": "http://xamarin.com/about/"
},

{ "Label"  :"Country3",
         "Address":"Multiline paragraph",
         "Lat":"-5", 
         "Lng":"45",
         "Name":"Xamarin",
         "Url": "http://xamarin.com/about/"
}

]

MapPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.Maps;
using Newtonsoft.Json;
using System.IO;
using Xamarin.Forms.Xaml;
using System.Reflection;    

namespace Orbage
{
    public partial class MapPage : ContentPage
    {
        public MapPage()
        {
            CustomMap customMap = new CustomMap
            {
                MapType = MapType.Hybrid


            };

            Content = customMap;

            var assembly = IntrospectionExtensions.GetTypeInfo(typeof(MapPage)).Assembly;
            Stream stream = assembly.GetManifestResourceStream("Orbage.Mydata.json");
            string json = "";
            using (var reader = new System.IO.StreamReader(stream))
            {
                json = reader.ReadToEnd();
            }
            var places = JsonConvert.DeserializeObject<List<Mydata>>(json);



            List<CustomPin> custompinList = new List<CustomPin>();
            foreach (var place in places)
            {
                CustomPin pin = new CustomPin
                {
                    Type = PinType.Place,
                    Position = new Position(Double.Parse(place.Lat), Double.Parse(place.Lng)),
                    Label = place.Label,
                    Address = place.Address,
                    Name = place.Name,
                    Url = place.Url
                };
                
                
                customMap.Pins.Add(pin);
                customMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(37.79752, -122.40183), Distance.FromMiles(1.0)));
                customMap.CustomPins = custompinList; 
            }
            

        }
    }
    public class Mydata
    {
        public string Label { get; set; }
        public string Address { get; set; }
        public string Lat { get; set; }
        public string Lng { get; set; }
        public string Name { get; set; }
        public string Url { get; set; }


    }
}

自定义引脚：

using System;
using System.Collections.Generic;
using System.Text;
using Xamarin.Forms.Maps;

namespace Orbage
{
    public class CustomPin : Pin
    {
        public string Name { get; set; }
        public string Url { get; set; }
        public string Adress { get; set; }
        public string Lat { get; set; }
        public string Lng { get; set; }
    }
}

自定义地图：

using System;
using System.Collections.Generic;
using System.Text;
using Xamarin.Forms.Maps;

namespace Orbage
{
    public class CustomMap : Map
    {
        public List<CustomPin> CustomPins { get; set; }
    }
}

CustomMapRenderer.cs：

using System;
using System.Collections.Generic;
using Android.Content;
using Android.Gms.Maps;
using Android.Gms.Maps.Model;
using Android.Widget;
using ----;
using ----.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Maps;
using Xamarin.Forms.Maps.Android;

[assembly: ExportRenderer(typeof(CustomMap), typeof(CustomMapRenderer))]
namespace ----.Droid
{
    public class CustomMapRenderer : MapRenderer, GoogleMap.IInfoWindowAdapter
    {
        List<CustomPin> customPins;

        public CustomMapRenderer(Context context) : base(context)
        {
        }

        protected override void OnElementChanged(Xamarin.Forms.Platform.Android.ElementChangedEventArgs<Map> e)
        {
            base.OnElementChanged(e);

            if (e.OldElement != null)
            {
                NativeMap.InfoWindowClick -= OnInfoWindowClick;
            }

            if (e.NewElement != null)
            {
                var formsMap = (CustomMap)e.NewElement;
                customPins = formsMap.CustomPins;
            }
        }

        protected override void OnMapReady(GoogleMap map)
        {
            base.OnMapReady(map);

            NativeMap.InfoWindowClick += OnInfoWindowClick;
            NativeMap.SetInfoWindowAdapter(this);
        }

        protected override MarkerOptions CreateMarker(Pin pin)
        {
            var marker = new MarkerOptions();
            marker.SetPosition(new LatLng(pin.Position.Latitude, pin.Position.Longitude));
            marker.SetTitle(pin.Label);
            marker.SetSnippet(pin.Address);
            marker.SetIcon(BitmapDescriptorFactory.FromResource(Resource.Drawable.pin));
            return marker;
        }

        void OnInfoWindowClick(object sender, GoogleMap.InfoWindowClickEventArgs e)
        {
            var customPin = GetCustomPin(e.Marker);
            if (customPin == null)
            {
                throw new Exception("Custom pin not found");
            }

            if (!string.IsNullOrWhiteSpace(customPin.Url))
            {
                var url = Android.Net.Uri.Parse(customPin.Url);
                var intent = new Intent(Intent.ActionView, url);
                intent.AddFlags(ActivityFlags.NewTask);
                Android.App.Application.Context.StartActivity(intent);
            }
        }

        public Android.Views.View GetInfoContents(Marker marker)
        {
            var inflater = Android.App.Application.Context.GetSystemService(Context.LayoutInflaterService) as Android.Views.LayoutInflater;
            if (inflater != null)
            {
                Android.Views.View view;

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

                if (customPin.Name.Equals("Xamarin"))
                {
                    view = inflater.Inflate(Resource.Layout.XamarinMapInfoWindow, null);
                }
                else
                {
                    view = inflater.Inflate(Resource.Layout.MapInfoWindow, null);
                }

                var infoTitle = view.FindViewById<TextView>(Resource.Id.InfoWindowTitle);
                var infoSubtitle = view.FindViewById<TextView>(Resource.Id.InfoWindowSubtitle);

                if (infoTitle != null)
                {
                    infoTitle.Text = marker.Title;
                }
                if (infoSubtitle != null)
                {
                    infoSubtitle.Text = marker.Snippet;
                }

                return view;
            }
            return null;
        }

        public Android.Views.View GetInfoWindow(Marker marker)
        {
            return null;
        }

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

感谢您看到这一点，我希望这个问题得到解答，并且有相同错误的人得到修复。:)

我尝试调试，这里是一些可能有所帮助的图像：

标签： c#androidxamarinxamarin.forms

  foreach (var place in places)
        {
            CustomPin pin = new CustomPin
            {
                Type = PinType.Place,
                Position = new Position(Double.Parse(place.Lat), Double.Parse(place.Lng)),
                Label = place.Label,
                Address = place.Address,
                Name = place.Name,
                Url = place.Url
            };
            customMap.CustomPins = new List<CustomPin> { pin }; //this will cause your customMap.CustomPins always has only the last custompin. 
            customMap.Pins.Add(pin);
            customMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(37.79752, -122.40183), Distance.FromMiles(1.0)));
        }

问题就在这里，你在循环中添加 customMap.CustomPins，所以它总是只有第三个 CustomPin。

尝试将其移出 foreach：

  List<CustomPin> custompinList = new List<CustomPin>();
  foreach (var place in places)
        {
            CustomPin pin = new CustomPin
            {
                Type = PinType.Place,
                Position = new Position(Double.Parse(place.Lat), Double.Parse(place.Lng)),
                Label = place.Label,
                Address = place.Address,
                Name = place.Name,
                Url = place.Url
            };
            custompinList.Add(pin);
            customMap.Pins.Add(pin);
            customMap.MoveToRegion(MapSpan.FromCenterAndRadius(new Position(37.79752, -122.40183), Distance.FromMiles(1.0)));
        }
  customMap.CustomPins = custompinList;

更新效果如下：

c# - 如何修复.Exception：'未找到特定引脚的自定义引脚

问题描述

解决方案

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