C# 表单：如何从WebAPI数据填充饼图？

大家好。我正在创建一个Xamarin.Forms可移植应用程序。我目前正在编写一个包含静态数据的PieChart（OxyPlot）

我想做的是在我拥有的每个饼图切片中都有一个动态数据。也就是说，数据应该来自我的数据库

我已经能够从数据库中检索数据，并在我使用Web Api创建的移动应用程序中以列表的形式显示数据，如下所示：

ClientListPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="XamarinFormsDemo.Views.ClientListPage"
             xmlns:ViewModels="clr-namespace:XamarinFormsDemo.ViewModels;assembly=XamarinFormsDemo"
             xmlns:controls="clr-namespace:ImageCircle.Forms.Plugin.Abstractions;assembly=ImageCircle.Forms.Plugin.Abstractions"
             BackgroundImage="bg3.jpg"
             Title="Client List1">


<StackLayout>

  <SearchBar Placeholder="Search" Text="{Binding Keyword}" SearchCommand="{Binding SearchCommand}" x:Name="txtSearch" />

    <ListView ItemsSource="{Binding CustomerList, Mode=TwoWay}"
              HasUnevenRows="True"
              IsPullToRefreshEnabled="True"
              x:Name="listView">


      <ListView.ItemTemplate>
        <DataTemplate>
          <ViewCell>
            <Grid Padding="10" RowSpacing="10" ColumnSpacing="5">
              <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="*"/>
              </Grid.RowDefinitions>
              <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="*"/>
              </Grid.ColumnDefinitions>

              <controls:CircleImage Source="icon.png"
                     HeightRequest="66"
                     HorizontalOptions="CenterAndExpand"
                     Aspect="AspectFill"
                     WidthRequest="66"
                     Grid.RowSpan="2"
                   />




              <Label Grid.Column="1"
                     Text="{Binding CUSTOMER_NAME}"
                     TextColor="#24e97d"
                     FontSize="24"/>



              <Label Grid.Column="1"
                      Grid.Row="1"
                       Text="{Binding CUSTOMER_CODE}"
                       TextColor="White"
                       FontSize="18"
                       Opacity="0.6"/>


              <Label Grid.Column="1"
                  Grid.Row="2"
                  Text="{Binding CUSTOMER_MOBILE_NUMBER}"
                   TextColor="White"
                   FontSize="18"
                   Opacity="0.6"/>


              <Label Grid.Column="1"
                  Grid.Row="3"
                  Text="{Binding CUSTOMER_EMAIL_ADDRESS}"
                   TextColor="White"
                   FontSize="18"
                   Opacity="0.6"/>


            </Grid>
          </ViewCell>
        </DataTemplate>
      </ListView.ItemTemplate>

    </ListView>
</StackLayout>


</ContentPage>

---

当您解析json并填充列表以输入listview时，您可以在viewmodel中填充该系列。一旦你有了客户对象的列表，浏览它们并根据需要使用它们的数据来创建饼图切片

以下几行中的某一行：

 var json = await GetCustomerAsync();
 var customers = JsonConvert.DeserializeObject<Customer[]>(json);

 dynamic seriesP1 = new PieSeries { StrokeThickness = 2.0, InsideLabelPosition = 0.8, AngleSpan = 360, StartAngle = 0 };

 foreach (Customer c in customers) {
    seriesP1.Slices.Add(new PieSlice(c.CustomerName, c.SomeValue) { IsExploded = false, Fill = OxyColors.Teal });
 }

var json=await GetCustomerAsync（）；
var customers=JsonConvert.DeserializeObject（json）；
动态系列P1=新系列{StrokeThickness=2.0，InsideLabelPosition=0.8，AngleSpan=360，StartAngle=0}；
foreach（客户中的客户c）{
seriesP1.Slices.Add（新的PieSlice（c.CustomerName，c.SomeValue）{isexploed=false，Fill=OxyColors.Teal}）；
}

我不知道你的客户类别是什么样的，你想展示什么样的价值观，等等。所以请记住这一点。这只是我的意思的一个例子。

---

另外，构造代码，使您只进行一次Http调用，然后将该客户列表用于列表和图表，不要下载两次数据，只是为了以两种不同的方式显示数据。

您正在将

PlotModel

分配给一个局部变量。您必须将其分配给您的

ViewModel

。以下是重构后的工作代码：

salerproductpage.xaml:

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:oxy="clr-namespace:OxyPlot.Xamarin.Forms;assembly=OxyPlot.Xamarin.Forms"
             xmlns:local="clr-namespace:App1"
             x:Class="App1.SalesPerProductPage">

  <ContentPage.Content>
      <oxy:PlotView Model="{Binding SalesPerProductModel}"></oxy:PlotView>
  </ContentPage.Content>

</ContentPage>

public partial class SalesPerProductPage : ContentPage
{
    public SalesPerProductViewModel viewModelforSales { get; set; }

    public SalesPerProductPage()
    {
        InitializeComponent();

        viewModelforSales = new SalesPerProductViewModel();
        BindingContext = viewModelforSales;
    }

    async protected override void OnAppearing()
    {
        base.OnAppearing();

        var json = await GetSalesPerProductAsync();

        var salesPerProduct = JsonConvert.DeserializeObject<Sales[]>(json);

        PlotModel modelForSales = new PlotModel
        {
            Title = "Sales Per Product",
            TitleColor = OxyColors.Teal,
            TitleFontSize = 30,
            TextColor = OxyColors.White,
            DefaultFont = "Arial Black",
            DefaultFontSize = 20

        };

        dynamic seriesP2 = new PieSeries { StrokeThickness = 2.0, InsideLabelPosition = 0.8, AngleSpan = 360, StartAngle = 0, FontSize = 24 };

        foreach (Sales c in salesPerProduct)
        {
            seriesP2.Slices.Add(new PieSlice(c.PRODUCT_CODE, c.PRODUCT_ID));
        }

        modelForSales.Series.Add(seriesP2);
        viewModelforSales.SalesPerProductModel = modelForSales;
    }

    async Task<string> GetSalesPerProductAsync()
    {
        var client = new HttpClient();

        client.BaseAddress = new Uri("http://10.0.0.17:64550/");

        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

        HttpResponseMessage response = await client.GetAsync("api/Sales");
        if (response.IsSuccessStatusCode)
        {
            return await response.Content.ReadAsStringAsync();
        }
        else return response.ReasonPhrase;
    }
}

public class SalesPerProductViewModel : INotifyPropertyChanged
{

    public event PropertyChangedEventHandler PropertyChanged = delegate { };

    private PlotModel _salesPerProductModel;
    public PlotModel SalesPerProductModel
    {
        get
        {
            return _salesPerProductModel;
        }
        set
        {
            if (value != _salesPerProductModel)
            {
                _salesPerProductModel = value;
                PropertyChanged(this, new PropertyChangedEventArgs("SalesPerProductModel"));
            }
        }
    }

    public SalesPerProductViewModel()
    {
    }
}

---

谢谢您的回答，先生。我的问题不在于客户，而在于销售。你所说的“下载两次数据只是为了以两种不同的方式显示”是什么意思？我只是在ClientListPage.xaml.cs中下载一次数据，然后对销售数据执行同样的操作。一旦你下载了用于销售的json并反序列化到一个对象，然后旋转它并为你的图表加载PieSicle对象。先生，我应该把这个放在哪里？foreach（customers中的Customer c）{seriesP1.Slices.Add（new PieSlice（c.CustomerName，c.SomeValue）{IsExploded=false，Fill=OxyColors.Teal}）}我已经为salerproductpage.xaml.cs添加了代码问题是，在

salerproductpage.xaml.cs

中，创建

modelForSales

，然后将其分配给本地

this.salerproductmodel

变量，而不是分配给

viewModelforSales.salerproductmodel

。此外，为了做到这一点，您必须将Sales.SalesPerProductModel的视图模型从

ObservableCollection

更改为

PlotModel

。还有一件事：出于测试目的，您的XAML中有

PlotView

本身。@jstreet先生，我如何将ObservableCollection转换为PlotModel？声明

SalesPerProductModel

为

PlotModel

，而不是

ObservableCollection

。您必须仅在

Portable

项目中执行此操作，而不是像以前那样在Web API中执行此操作。@jstreet先生，我是这样做的。就在OnAppearing方法下面。我做得对吗？不，你在改变一个局部变量。。。。您必须更改销售的

model.salerproductmodel

。先生，我的应用程序中只显示了salerproduct标题？请从XAML中删除任何

标签

，只保留

绘图视图

，就像我发布的XAML一样。此外，使用调试器验证您是否使用有效数据正确添加了饼图切片。先生，我设置了一些断点，发现我的产品ID返回的值为零值，这就是为什么我无法创建切片。您必须检查的第一件事是

OnAppearing（）

中的

var json

的内容。

using OxyPlot;
using OxyPlot.Xamarin.Forms;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using XamarinFormsDemo.ViewModels;
using Xamarin.Forms;
using XamarinFormsDemo.Models;
using Newtonsoft.Json;
using System.Net.Http;
using System.Net.Http.Headers;
using OxyPlot.Series;

namespace XamarinFormsDemo.Views
{
    public partial class SalesPerProductPage : ContentPage
    {
        private PlotModel modelForSales;
        SalesPerProductViewModel viewModelforSales;

        public SalesPerProductPage()
        {
            InitializeComponent();
            viewModelforSales = new SalesPerProductViewModel();
            BindingContext = viewModelforSales;


        } //end of SalesPerProductPage()


        async override protected void OnAppearing()
        {
            base.OnAppearing();

            var json = await GetSalesPerProductAsync();

            var salesPerProduct = JsonConvert.DeserializeObject<Sales[]>(json);

            modelForSales = new PlotModel
            {
                Title = "Sales Per Product",
                TitleColor = OxyColors.Teal,
                TitleFontSize = 30,
                TextColor = OxyColors.White,
                DefaultFont = "Arial Black",
                DefaultFontSize = 20

            };

            dynamic seriesP2 = new PieSeries { StrokeThickness = 2.0, InsideLabelPosition = 0.8, AngleSpan = 360, StartAngle = 0 };

            foreach (Sales c in salesPerProduct)
            {
                seriesP2.Slices.Add(new PieSlice(c.PRODUCT_CODE, c.PRODUCT_ID) { IsExploded = false, Fill = OxyColors.Teal });
            }

            modelForSales.Series.Add(seriesP2);
            this.SalesPerProductModel = modelForSales;
        }

        public PlotModel SalesPerProductModel { get; private set; }

        async Task<string> GetSalesPerProductAsync()
        {
            var client = new HttpClient();

            client.BaseAddress = new Uri("http://192.168.1.11:50857/");

            client.DefaultRequestHeaders.Accept.Clear();
            client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            HttpResponseMessage response = await client.GetAsync("api/Sales");
            if (response.IsSuccessStatusCode)
            {
                return await response.Content.ReadAsStringAsync();
            }
            else return response.ReasonPhrase;
        }


    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace XamarinFormsDemo.Models
{
    public class Sales
    {
        public int Id { get; set; }
        public int ORDER_ID { get; set; }
        public int ORDER_DETAILS_ID { get; set; }
        public int PRODUCT_ID { get; set; }
        public string PRODUCT_CODE { get; set; }
        public string NET_AMOUNT { get; set; }
    }
}

 var json = await GetCustomerAsync();
 var customers = JsonConvert.DeserializeObject<Customer[]>(json);

 dynamic seriesP1 = new PieSeries { StrokeThickness = 2.0, InsideLabelPosition = 0.8, AngleSpan = 360, StartAngle = 0 };

 foreach (Customer c in customers) {
    seriesP1.Slices.Add(new PieSlice(c.CustomerName, c.SomeValue) { IsExploded = false, Fill = OxyColors.Teal });
 }

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:oxy="clr-namespace:OxyPlot.Xamarin.Forms;assembly=OxyPlot.Xamarin.Forms"
             xmlns:local="clr-namespace:App1"
             x:Class="App1.SalesPerProductPage">

  <ContentPage.Content>
      <oxy:PlotView Model="{Binding SalesPerProductModel}"></oxy:PlotView>
  </ContentPage.Content>

</ContentPage>

public partial class SalesPerProductPage : ContentPage
{
    public SalesPerProductViewModel viewModelforSales { get; set; }

    public SalesPerProductPage()
    {
        InitializeComponent();

        viewModelforSales = new SalesPerProductViewModel();
        BindingContext = viewModelforSales;
    }

    async protected override void OnAppearing()
    {
        base.OnAppearing();

        var json = await GetSalesPerProductAsync();

        var salesPerProduct = JsonConvert.DeserializeObject<Sales[]>(json);

        PlotModel modelForSales = new PlotModel
        {
            Title = "Sales Per Product",
            TitleColor = OxyColors.Teal,
            TitleFontSize = 30,
            TextColor = OxyColors.White,
            DefaultFont = "Arial Black",
            DefaultFontSize = 20

        };

        dynamic seriesP2 = new PieSeries { StrokeThickness = 2.0, InsideLabelPosition = 0.8, AngleSpan = 360, StartAngle = 0, FontSize = 24 };

        foreach (Sales c in salesPerProduct)
        {
            seriesP2.Slices.Add(new PieSlice(c.PRODUCT_CODE, c.PRODUCT_ID));
        }

        modelForSales.Series.Add(seriesP2);
        viewModelforSales.SalesPerProductModel = modelForSales;
    }

    async Task<string> GetSalesPerProductAsync()
    {
        var client = new HttpClient();

        client.BaseAddress = new Uri("http://10.0.0.17:64550/");

        client.DefaultRequestHeaders.Accept.Clear();
        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

        HttpResponseMessage response = await client.GetAsync("api/Sales");
        if (response.IsSuccessStatusCode)
        {
            return await response.Content.ReadAsStringAsync();
        }
        else return response.ReasonPhrase;
    }
}

public class SalesPerProductViewModel : INotifyPropertyChanged
{

    public event PropertyChangedEventHandler PropertyChanged = delegate { };

    private PlotModel _salesPerProductModel;
    public PlotModel SalesPerProductModel
    {
        get
        {
            return _salesPerProductModel;
        }
        set
        {
            if (value != _salesPerProductModel)
            {
                _salesPerProductModel = value;
                PropertyChanged(this, new PropertyChangedEventArgs("SalesPerProductModel"));
            }
        }
    }

    public SalesPerProductViewModel()
    {
    }
}