在我的应用程序上显示来自 JSON 本地文件的数据

Question

我有一个本地 JSON 文件，我需要在我的应用程序上显示它的一些数据，我尝试了一些解决方案但没有任何反应，我在另一个“Lighter”的 JSON 文件上尝试了以下代码，它有效，但它不适用于我的主要 JSON 文件。

这是我的 JSON 文件：

{
  "latitude": 49.241524,
  "longitude": 4.063723,
  "glcParts": [
    {
      "id": 1,
      "coordinates": [
        {
          "latitude": 49.241527,
          "longitude": 4.063755
        },
        {
          "latitude": 49.241545,
          "longitude": 4.063865
        },
        {
          "latitude": 49.241543,
          "longitude": 4.063995
        },
        {
          "latitude": 49.241537,
          "longitude": 4.064188
        }
      ]
    },
    {
      "id": 2,
      "coordinates": [
        {
          "latitude": 49.241555,
          "longitude": 4.063413
        },
        {
          "latitude": 49.241571,
          "longitude": 4.063260
        },
        {
          "latitude": 49.241589,
          "longitude": 4.063032
        },
        {
          "latitude": 49.241600,
          "longitude": 4.062884
        }
      ]
    }
  ],
  "gicParts": [
    {
      "detectionZoneId": 1,
      "relevanceZoneId": 2,
      "direction": 0,
      "iviType": 0,
      "roadSign": [
        {
          "countryCode": "FR",
          "trafficSignPictogram": 2,
          "pictogramCategoryCode": {
            "nature": 6,
            "serialNumber": 61
          }
        }
      ],
      "extraText": [
        {
          "language": 714,
          "content": "Rétrécissement"
        },
        {
          "language": 714,
          "content": "voie"
        }

      ]
    },
    {
      "detectionZoneId": 1,
      "relevanceZoneId": 2,
      "direction": 0,
      "iviType": 1,
      "roadSign": [
        {
          "countryCode": "FR",
          "trafficSignPictogram": 2,
          "pictogramCategoryCode": {
            "nature": 5,
            "serialNumber": 57
          }
        }
      ],
      "extraText": [
        {
          "language": 714,
          "content": "/!\\ 50 km/h"
        }
      ]
    }
  ],
  "timeStamp": "2019-03-08T16:00:00+01:00",
  "validFrom": "2019-03-08T16:00:00+01:00",
  "validTo": "2019-03-08T18:00:00+01:00",
  "countryCode": 714,
  "providerIdentifier": 4201,
  "status": 0
}

C# 类：

using System;
using System.Collections.Generic;

namespace interface_test
{
    public class Coordinate
    {
        public double latitude { get; set; }
        public double longitude { get; set; }
    }

    public class GlcPart
    {
        public int id { get; set; }
        public List<Coordinate> coordinates { get; set; }
    }

    public class PictogramCategoryCode
    {
        public int nature { get; set; }
        public int serialNumber { get; set; }
    }

    public class RoadSign
    {
        public string countryCode { get; set; }
        public int trafficSignPictogram { get; set; }
        public PictogramCategoryCode pictogramCategoryCode { get; set; }
    }

    public class ExtraText
    {
        public int language { get; set; }
        public string content { get; set; }
    }

    public class GicPart
    {
        public int detectionZoneId { get; set; }
        public int relevanceZoneId { get; set; }
        public int direction { get; set; }
        public int iviType { get; set; }
        public List<RoadSign> roadSign { get; set; }
        public List<ExtraText> extraText { get; set; }
    }

    public class IVIv2
    {
        public double latitude { get; set; }
        public double longitude { get; set; }
        public List<GlcPart> glcParts { get; set; }
        public List<GicPart> gicParts { get; set; }
        public DateTime timeStamp { get; set; }
        public DateTime validFrom { get; set; }
        public DateTime validTo { get; set; }
        public int countryCode { get; set; }
        public int providerIdentifier { get; set; }
        public int status { get; set; }
    }
}

主类：

using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using interface_test;
using Newtonsoft.Json;
using Xamarin.Forms;

namespace interface_test
{
    public partial class IVI_Display : ContentPage
    {
        public IVI_Display()
        {
            InitializeComponent();
            GetJsonData();
        }
        void GetJsonData()
        {
            string jsonFileName = "JsonIVI.json";
            GlcPart ObjContactList = new GlcPart();
            var assembly = typeof(IVI_Display).GetTypeInfo().Assembly;
            Stream stream = assembly.GetManifestResourceStream($"{assembly.GetName().Name}.{jsonFileName}");
            using (var reader = new StreamReader(stream))
            {
                var jsonString = reader.ReadToEnd();

                //Converting JSON Array Objects into generic list    
                ObjContactList = JsonConvert.DeserializeObject<GlcPart>(jsonString);
            }
            //Binding listview with json string     
            listviewGLC.ItemsSource = ObjContactList.coordinates;
        }

    }
}

XAML 显示：

 <ListView x:Name="listviewGLC" Grid.Row="1" HorizontalOptions="FillAndExpand" Footer="" HasUnevenRows="True">  
                <ListView.ItemTemplate>  
                    <DataTemplate>  
                        <ViewCell>  
                            <Grid HorizontalOptions="FillAndExpand" Padding="10">  
                                <Grid.RowDefinitions>  
                                    <RowDefinition Height="Auto"/>  
                                    <RowDefinition Height="Auto"/>  


                                </Grid.RowDefinitions>  
                                <Label Text="{Binding latitude}" HorizontalOptions="StartAndExpand" Grid.Row="0" TextColor="Blue"  FontAttributes="Bold"/>  
                                <Label Text="{Binding longitude}" HorizontalOptions="StartAndExpand" Grid.Row="0" TextColor="Blue"  FontAttributes="Bold"/>  

                                <BoxView HeightRequest="2" Margin="0,10,10,0" BackgroundColor="Gray" Grid.Row="2" HorizontalOptions="FillAndExpand" />  
                            </Grid>  
                        </ViewCell>  

                    </DataTemplate>  
                </ListView.ItemTemplate>  
            </ListView>  

作为结果，我希望显示纬度和经度，但我什么也没得到

Answer 1

根据您的 json，您应该在 IVIv2 对象中反序列化它，而不是在 GlcPart 中。

替换：ObjContactList = JsonConvert.DeserializeObject<GlcPart>(jsonString);

与：ObjContactList = JsonConvert.DeserializeObject<IVIv2>(jsonString);

然后你的

listviewGLC.ItemsSource = ObjContactList.GlcPart[0];

使用您当前的模型结构，您无法创建包含 GlcPart 列表中所有值的列表视图。

Answer 2

ObjContactList 必须是用于在 xaml 中绑定的公共属性

我建议使用清晰的代码将 ViewModel 添加到 ContentPage 类并使用 Bindingcontext。

public partial class IVI_Display : ContentPage
{
    public IVI_DisplayViewModel ViewModel { get; set; }

   public IVI_Display()
   {
        ViewModel = new IVI_DisplayViewModel();
        ...
        BindingContext = ViewModel;
   }    


}

public class IVI_DisplayViewModel
{
    public object Coordinates { get; set; }
    ...
}

在 Xaml 中使用

<ListView x:Name="listviewGLC" ItemsSource="{Binding Coordinates} Grid.Row="1" HorizontalOptions="FillAndExpand" Footer="" HasUnevenRows="True">  

输入清晰的代码总是一个好习惯。