UWP Gridview绑定到ObservableCollection并清除值 [英] UWP Gridview Binding to ObservableCollection and clearing values

问题描述

所以我要在绑定到ObservableCollection的UWP应用中创建GridView.

so I am creating a GridView in a UWP app which is bound to an ObservableCollection.

XAML:

<Page.Resources>
    <CollectionViewSource
            x:Name="ListSource"
            Source="{x:Bind model.ShowList}"
            IsSourceGrouped="false"
            />
</Page.Resources>
...
<Page>
    <GridView x:Name="lvListSource" ItemsSource="{Binding Source={StaticResource ListSource}}" SelectedIndex="-1" Grid.Row="2" HorizontalContentAlignment="Center" SelectionChanged="lvEpisodeListSource_SelectionChanged">
                <GridView.ItemTemplate>
                    <DataTemplate x:DataType="local:PageInput">
                        <TextBlock Name="AlbumBlock" Foreground="Black" FontWeight="Normal" FontSize="15" Margin="5,0,5,0"
                                    Text="{x:Bind Name}" HorizontalAlignment="Left" VerticalAlignment="Center" Width="100"/>
                    </DataTemplate>
                </GridView.ItemTemplate>
            </GridView>
</page>

C#:

public MainCategoryModel model;
public MainPage()
{
    model = new MainCategoryModel();
    this.InitializeComponent();
}

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    //initialize model data in code and stuff comes out correctly
    //model.Clear() give unknown error here
    model.Add(new PageInput() {...});
    lvListSource.ItemsSource = model.myList;
}

public class MainCategoryModel
{
    public ObservableCollection<PageInput> myList { get; set; }

    public MainCategoryModel()
    {
        myList = new ObservableCollection<PageInput>();
    }

    public void AddShow(PageInput show)
    {
        myList.Insert(0, show);
    }

    public void Clear()
    {
        myList.Clear();
    }
}

当我仅将项目添加到集合时，ObservableCollection会正确初始化，并且页面加载非常好.问题是，我希望每次调用OnNavigatedTo函数时都将GridView绑定到此ObservableCollection.这包括从集合中删除项目.每次我删除项目或尝试清除ObservableCollection时，页面均无法加载，并出现未知错误.有没有办法从已经绑定的Observable集合中修改和删除值?

The ObservableCollection initializes properly and the page loads perfectly fine when I only add items to the collection. The problem is, I would like to update this ObservableCollection the GridView is bound to every time the OnNavigatedTo function is called. This includes removing items from the collection. Every time I either remove items or try to Clear the ObservableCollection the page fails to load with an unknown error. Is there a way to modify and remove values from an Observable Collection that is already bound to?

作为一个附带的问题，如果我没有在OnNavigatedTo的末尾重新设置ItemsSource属性，则将值添加到Collection之后会立即调用SelectionChanged事件，因为它是在XAML中设置的.将项目添加到GridView时，是否有一种方法可以使SelectionChanged事件不被调用?

As a side problem, If I don't re-set the ItemsSource property at the end of OnNavigatedTo, the SelectionChanged event is called immediately after adding values to the Collection since it is set in XAML. Is there a way to have the SelectionChanged event not call when items are added to a GridView?

推荐答案

x:默认情况下，绑定是OneTime，您需要将其设置为Mode = OneWay以获取布局更新

x:Bind is OneTime by default, you need to set it Mode=OneWay to get the layout updates

   protected override void OnNavigatedTo(NavigationEventArgs e)
   {
       //initialize model data in code and stuff comes out correctly

      lvEpisodeListSource.ItemsSource = model.myList;
   }

杀死您的绑定，更新model.myList并让绑定完成任务，如果您希望将其绑定，请不要通过代码设置ItemsSource

kills your binding, update model.myList and let the binding do the job, don't set ItemsSource from code this way if you want it to be binded

复制并运行您的代码(这不是令人愉快的经历，因为您没有把它弄干净)，我也不明白为什么您的代码中的Binding和x:Bind如此混乱，为什么不你只是这样绑定收藏?

copied and run your code (which wasn't pleasant experience because you didn't make it clean) and I don't undersand why there is such mess with the Binding and x:Bind in your code, why don't you just bind the collection like that?

<GridView x:Name="lvListSource" ItemsSource="{x:Bind model.myList, Mode=OneWay}" ....

edit2:

我的代码:

public class MainCategoryModel
{
    public ObservableCollection<PageInput> myList { get; set; }

    public MainCategoryModel()
    {
        myList = new ObservableCollection<PageInput>();
    }

    public void AddShow(PageInput show)
    {
        myList.Insert(0, show);
    }

    public void Clear()
    {
        myList.Clear();
    }
}

<Page>
(........)
    <GridView x:Name="lvListSource" ItemsSource="{x:Bind model.myList, Mode=OneWay}" SelectedIndex="-1" Grid.Row="2" HorizontalContentAlignment="Center">
    <GridView.ItemTemplate>
        <DataTemplate x:DataType="local:PageInput">
            <TextBlock Name="AlbumBlock" Foreground="Black" FontWeight="Normal" FontSize="15" Margin="5,0,5,0"
                                Text="{x:Bind Name}" HorizontalAlignment="Left" VerticalAlignment="Center" Width="100"/>
        </DataTemplate>
    </GridView.ItemTemplate>
</GridView>

public sealed partial class MainPage : Page
{
    public MainCategoryModel model;
    public MainPage()
    {
        model = new MainCategoryModel();
        this.InitializeComponent();
    }

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        model.Clear();
        model.myList.Add(new PageInput() {Name = "testName"});
    }

}

，由quess制作:

public class PageInput
{
    public string Name { get; set; }
}

尝试运行并检查它

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