Xamarin ListView不显示任何数据

Question

我有一个问题，当我尝试在我的应用程序中显示ListView中的数据时，将数据列表绑定到XAML中的ListView中。 ListView不会填充任何数据。

这里是我的所有编码：

我代码隐藏

public ObservableCollection<RandomList> randomList = new ObservableCollection<RandomList>(); 

public App() 
{ 
    MainPage = new MainUI(); 

    randomList.Add(new RandomList { Name = "Susan", Surname = "Potgieter", School = "Oosterlig" }); 
    randomList.Add(new RandomList { Name = "Jonathan", Surname = "Visagie", School = "Elspark" }); 
    randomList.Add(new RandomList { Name = "Gerhard", Surname = "Vermaak", School = "E.G. Jansen" }); 
    randomList.Add(new RandomList { Name = "Kobus", Surname = "Jacobs", School = "Oosterlig" });   
} 

我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="RandomTest.MainUI"> 
    <StackLayout Padding="0,40,0,0"> 
    <Label Text="Hello" VerticalOptions="Center" HorizontalOptions="Center" /> 
    <Button x:Name="btnGetStudents" Text="Get Students"/> 
    <ListView x:Name="lwStudents" ItemsSource="{Binding randomList}"> 
     <ListView.ItemTemplate> 
     <DataTemplate> 
      <TextCell Text="{Binding Name}" Detail="{Binding Surname}"/> 
     </DataTemplate> 
     </ListView.ItemTemplate> 
    </ListView> 
    </StackLayout> 
</ContentPage> 

当我在我的代码中插入一个断点是后面我将虚拟数据添加到列表中，然后我可以在我的XAML中看到：<ListView x:Name="lwStudents" ItemsSource="{Binding randomList}">在我的randomList中有4个项目。

的问题是，有如下两个绑定没有数据：

<TextCell Text="{Binding Name}" Detail="{Binding Surname}"/> 

有人能告诉或告诉我什么，我做错了，我结合？或者，如果您需要更多信息或代码，请询问！我会很乐意提供更多信息。 :)

编辑

我已经更新了我RandomList类和实现INotifyPropertyChanged，但我还是不能让我的数据在我的ListView通过XAML绑定加载。

using System.ComponentModel; 

namespace RandomTest 
{ 
    public class RandomList : INotifyPropertyChanged 
    { 
     public int Id { get; set; } 

     string _name; 
     public string Name 
     { 
      get { return _name; } 
      set 
      { 
       if (_name != value) 
        _name = value; 
       OnPropertyChanged("Name"); 
      } 
     } 

     string _surname; 
     public string Surname 
     { 
      get { return _surname; } 
      set 
      { 
       if (_surname != value) 
        _surname = value; 
       OnPropertyChanged("Surname"); 
      } 
     } 

     string _school; 
     public string School 
     { 
      get { return _school; } 
      set 
      { 
       if (_school != value) 
        _school = value; 
       OnPropertyChanged("School"); 
      } 
     } 

     public event PropertyChangedEventHandler PropertyChanged; 
     void OnPropertyChanged(string propertyName) 
     { 
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); 
     } 
    } 
} 

EDIT 2

这是我MainUI.xaml.cs页面的外观像此刻：

public partial class MainUI : ContentPage 
{ 
    public MainUI() 
    { 
     InitializeComponent(); 
     BindingContext = new MainUIModel(); 

     MainUIModel mainUIModel = (MainUIModel)this.BindingContext; 
     mainUIModel.randomList.Add(new RandomList { Name = "Susan", Surname = "Potgieter", School = "Oosterlig" }); 
     mainUIModel.randomList.Add(new RandomList { Name = "Jonathan", Surname = "Visagie", School = "Elspark" }); 
     mainUIModel.randomList.Add(new RandomList { Name = "Gerhard", Surname = "Vermaak", School = "E.G. Jansen" }); 
     mainUIModel.randomList.Add(new RandomList { Name = "Kobus", Surname = "Jacobs", School = "Oosterlig" }); 
    } 
} 

Answer 1

创建一个模型MainUIModel

public class MainUIModel : INotifyPropertyChanged 
{ 
    ObservableCollection<RandomList> _randomList; 
    public ObservableCollection<RandomList> randomList 
    { 
     get { return _randomList; } 
     set 
     { 
      if (_randomList != value) 
       _randomList = value; 
      OnPropertyChanged("randomList"); 
     } 
    } 


    public event PropertyChangedEventHandler PropertyChanged; 
    void OnPropertyChanged(string propertyName) 
    { 
     PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); 
    } 
} 

而且那么在初始化compo之后，在你的MainUI页面中设置绑定上下文新界东北堆填区。

BindingContext = new MainUIModel(); 

Xaml中的绑定randomList将引用这个新创建的模型，并且您的Name，Surname将引用列表模型。两个绑定上下文都不同。您可以使用下面的代码添加您的数据。

MainUIModel mainUIModel = (MainUIModel)this.BindingContext; 
mainUIModel.randomList=new ObservableCollection<RandomList>(); 
    mainUIModel.randomList.Add(new RandomList { Name = "Susan", Surname = "Potgieter", School = "Oosterlig" }); 
    mainUIModel.randomList.Add(new RandomList { Name = "Jonathan", Surname = "Visagie", School = "Elspark" }); 
    mainUIModel.randomList.Add(new RandomList { Name = "Gerhard", Surname = "Vermaak", School = "E.G. Jansen" }); 
    mainUIModel.randomList.Add(new RandomList { Name = "Kobus", Surname = "Jacobs", School = "Oosterlig" });