C# 和 XAML 中的多种格式类型列表视图 [英] Multiple format types listview in C# and XAML

问题描述

我正在创建一个带有显示消息对象的列表视图的消息传递应用程序.

当新用户加入时，我想添加(例如)约翰加入"，但我希望它的格式与消息不同.

我怎样才能做到这一点?

解决方案

对于这种情况，您可以实施

I am creating a messaging application with a listview that displays message objects.

When a new user joins, I want to add (for example) "John joined" but I want it to be formatted differently than a message.

How can I achieve this?

解决方案

For this scenario, you can implement the ItemsControl.ItemTemplateSelector property of the ListView.

For example, create a class inherit from DataTemplateSelector first like this:

public class MessageDataTemplateSelecotr : DataTemplateSelector
{
    public DataTemplate NormalTemplate { get; set; }
    public DataTemplate JoinedTemplate { get; set; }
    protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
    {
        var message = item as MessageModel;
        if (message.MessageType.ToString() == "Normal")
            return NormalTemplate;
        else
            return JoinedTemplate;
    }
}

Then you can use this selector for example like this:

<Page.Resources>
    <DataTemplate x:Key="NormalMessageTemplate">
        <TextBlock Text="{Binding Message}" FontSize="20" Foreground="Blue"/>
    </DataTemplate>
    <DataTemplate x:Key="JoinedMessageTemplate">
        <TextBlock Text="{Binding Message}" FontSize="15" Foreground="Red"/>
    </DataTemplate>
    <local:MessageDataTemplateSelecotr x:Key="MessageDataTemplateSelecotr" 
                                       NormalTemplate="{StaticResource NormalMessageTemplate}" 
                                       JoinedTemplate="{StaticResource JoinedMessageTemplate}"/>
</Page.Resources>

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <ListView ItemTemplateSelector="{StaticResource MessageDataTemplateSelecotr}" ItemsSource="{x:Bind listViewCollection}"/>
</Grid>

In the code behind just add data into the listViewCollection like this:

ObservableCollection<MessageModel> listViewCollection = new ObservableCollection<MessageModel>();
private enum _MessageType
{
    Normal,
    Joined
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
    listViewCollection.Add(new MessageModel { Message = "hello world!", MessageType = _MessageType.Normal });
    listViewCollection.Add(new MessageModel { Message = "John joined", MessageType = _MessageType.Joined });
}

And my MessageModel class is like this:

public class MessageModel
{
    public string Message { get; set; }
    public Enum MessageType { get; set; }
}

The rendering image of this ListView is here:

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