C# WPF-ListView中的绑定'；s ItemsSource不能是列表

我有一个WPF应用程序，我尝试使用MVVM编写它。目标是创建一个类似于通知中心的东西，它列出不同类型的数据

为此，我想用不同的视图模型填充主页上的ListView。每种数据类型一个ViewModel

问题是： 当我在ListView中放置一个（不是列表）ViewModel时，它可以正常工作。但是如果我在ListView中放入一个列表，程序在启动时就会崩溃。我需要ListView获取混合视图模型的列表（可能是ObservableCollection）

我在代码中的一个看似随机的位置收到错误“在使用ItemsSource之前，Items集合必须为空”。完全删除出现异常的代码只会导致它显示在其他地方

我有以下资料：

C#：

public class MainViewModel : ObservableObject
{
    private List<IPageViewModel> _items;

    public MainViewModel()
    {
        _items = new List<IPageViewModel>
        {
            new StatusViewModel(),
            new SettingsViewModel(),
            new OverviewViewModel()
        };
    }

    public List<IPageViewModel> Items => _items ?? (_items = newList<IPageViewModel>());
}

<Window x:Class="InfoCenter.Views.Main.MainView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:test="clr-namespace:InfoCenter.Views.Test"
        xmlns:main="clr-namespace:InfoCenter.Views.Main"
        xmlns:views="clr-namespace:InfoCenter.Views"
        xmlns:settings="clr-namespace:InfoCenter.Views.Settings"
        xmlns:status="clr-namespace:InfoCenter.Views.Status"
        xmlns:overview="clr-namespace:InfoCenter.Views.Overview"
        mc:Ignorable="d"
        Title="MainView" Height="450" Width="500" 
        MaxWidth="1920"
        WindowStyle="None" Loaded="MainViewLoaded" 
        SizeChanged="MainViewSizeChanged"
        PreviewKeyDown="OnPreviewKeyDown"
        GotFocus="OnGotFocus"
        Closing="OnClosing"
        ResizeMode="NoResize"
        d:DataContext="{d:DesignInstance main:MainViewModel}">

    <Window.Resources>
        <DataTemplate DataType="{x:Type overview:OverviewViewModel}">
            <overview:OverviewView />
        </DataTemplate>
        <DataTemplate DataType="{x:Type status:StatusViewModel}">
            <status:StatusView />
        </DataTemplate>
        <DataTemplate DataType="{x:Type settings:SettingsViewModel}">
            <settings:SettingsView />
        </DataTemplate>
    </Window.Resources>


    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="24" />
            <RowDefinition Height="*" />
            <RowDefinition Height="30" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="24" />
        </Grid.ColumnDefinitions>

        <Button Command="{Binding ButtonClickCommand}" CommandParameter="Minimize" Grid.Row="0" Grid.Column="1">
            <Image Source="/Resources/arrow-down-1.png"></Image>
        </Button>

        <ListView ItemsSource="{Binding Items}" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" ScrollViewer.HorizontalScrollBarVisibility="Hidden" PreviewMouseWheel="OnPreviewMouseWheel" ScrollViewer.VerticalScrollBarVisibility="Hidden">
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="30" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>

                <Label Grid.Row="0" Grid.Column="0" Content="{Binding Path=Items.Header}" />
                <ContentControl Grid.Row="1" Grid.Column="0" Content="{Binding}" />
            </Grid>

        </ListView>

        <StatusBar FlowDirection="RightToLeft" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="2">
            <Image Width="24" Height="24" Source="{Binding ConnectionIcon}" />
        </StatusBar>

    </Grid>
</Window>

public类主视图模型：observeObject
{
私人物品清单；
公共主视图模型（）
{
_项目=新列表
{
新的StatusViewModel（），
新设置ViewModel（），
新的概览模型（）
};
}
公共列表项=>\u项？？？（\u项=newList（））；
}

XAML:

public class MainViewModel : ObservableObject
{
    private List<IPageViewModel> _items;

    public MainViewModel()
    {
        _items = new List<IPageViewModel>
        {
            new StatusViewModel(),
            new SettingsViewModel(),
            new OverviewViewModel()
        };
    }

    public List<IPageViewModel> Items => _items ?? (_items = newList<IPageViewModel>());
}

<Window x:Class="InfoCenter.Views.Main.MainView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:test="clr-namespace:InfoCenter.Views.Test"
        xmlns:main="clr-namespace:InfoCenter.Views.Main"
        xmlns:views="clr-namespace:InfoCenter.Views"
        xmlns:settings="clr-namespace:InfoCenter.Views.Settings"
        xmlns:status="clr-namespace:InfoCenter.Views.Status"
        xmlns:overview="clr-namespace:InfoCenter.Views.Overview"
        mc:Ignorable="d"
        Title="MainView" Height="450" Width="500" 
        MaxWidth="1920"
        WindowStyle="None" Loaded="MainViewLoaded" 
        SizeChanged="MainViewSizeChanged"
        PreviewKeyDown="OnPreviewKeyDown"
        GotFocus="OnGotFocus"
        Closing="OnClosing"
        ResizeMode="NoResize"
        d:DataContext="{d:DesignInstance main:MainViewModel}">

    <Window.Resources>
        <DataTemplate DataType="{x:Type overview:OverviewViewModel}">
            <overview:OverviewView />
        </DataTemplate>
        <DataTemplate DataType="{x:Type status:StatusViewModel}">
            <status:StatusView />
        </DataTemplate>
        <DataTemplate DataType="{x:Type settings:SettingsViewModel}">
            <settings:SettingsView />
        </DataTemplate>
    </Window.Resources>


    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="24" />
            <RowDefinition Height="*" />
            <RowDefinition Height="30" />
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="24" />
        </Grid.ColumnDefinitions>

        <Button Command="{Binding ButtonClickCommand}" CommandParameter="Minimize" Grid.Row="0" Grid.Column="1">
            <Image Source="/Resources/arrow-down-1.png"></Image>
        </Button>

        <ListView ItemsSource="{Binding Items}" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" ScrollViewer.HorizontalScrollBarVisibility="Hidden" PreviewMouseWheel="OnPreviewMouseWheel" ScrollViewer.VerticalScrollBarVisibility="Hidden">
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="30" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>

                <Label Grid.Row="0" Grid.Column="0" Content="{Binding Path=Items.Header}" />
                <ContentControl Grid.Row="1" Grid.Column="0" Content="{Binding}" />
            </Grid>

        </ListView>

        <StatusBar FlowDirection="RightToLeft" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="2">
            <Image Width="24" Height="24" Source="{Binding ConnectionIcon}" />
        </StatusBar>

    </Grid>
</Window>

我真的希望你能帮忙。我一整天都在努力修好它

您在这里的

列表视图

内容中放了一个东西：一个

网格

控件。不要那样做。有两种方法可以在XAML中填充ListView：绑定

ItemsSource

或将项目放入

ListView

元素的内容中。你不能同时做这两件事，而你同时做了这两件事，所以它抛出了一个异常

这是ItemsSource版本

<ListView 
    ItemsSource="{Binding Items}" 
    Grid.Row="1" 
    Grid.Column="0" 
    Grid.ColumnSpan="2" 
    ScrollViewer.HorizontalScrollBarVisibility="Hidden" 
    PreviewMouseWheel="OnPreviewMouseWheel" 
    ScrollViewer.VerticalScrollBarVisibility="Hidden"
    />

---

基于这个错误，我建议更改您的XAML，正如前面在中提到的那样

试试这个XAML：

     <ListView ItemsSource="{Binding Items}" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" ScrollViewer.HorizontalScrollBarVisibility="Hidden" PreviewMouseWheel="OnPreviewMouseWheel" ScrollViewer.VerticalScrollBarVisibility="Hidden">
         <ListView.View>
            <Grid>
                <Grid.RowDefinitions>
                    <RowDefinition Height="30" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>

                <Label Grid.Row="0" Grid.Column="0" Content="{Binding Path=Items.Header}" />
                <ContentControl Grid.Row="1" Grid.Column="0" Content="{Binding}" />
            </Grid>
       </ListView.View>
     </ListView>

---

希望这会有帮助

是的，IPageViewModel有一个Header属性，我想使用网格以某种方式显示项目。您的ItemTemplate解决方案完成了任务。非常感谢你！这不是有效的XML。