WinUI 3 ListView -如何在ListView中以编程方式选择项目？
WinUI 3 ListView -如何在ListView中以编程方式选择项目？
提问于 2022-11-16 06:43:54
如果用户与代码后面添加/删除的列表视图交互，那么我们有一个可观察的集合SelectedPartys。
<ListView
x:Name="LV_Partys"
IsMultiSelectCheckBoxEnabled="True"
ItemsSource="{x:Bind ViewModel.PartysOC, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
SelectionChanged="LV_Partys_SelectionChanged"
SelectionMode="Extended">
<ListView.ItemTemplate>
<DataTemplate>
<Grid Margin="0">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<StackPanel Grid.Row="0" Orientation="Horizontal">
<TextBlock Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}" TextWrapping="NoWrap" />
</StackPanel>
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>private ObservableCollection<Party> partysOC;
public ObservableCollection<Party> PartysOC
{
get => partysOC;
set => Set(ref partysOC, value);
}
private void LV_Partys_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var added_items = e.AddedItems.Cast<Party>().ToList();
foreach (var item in added_items)
{
ViewModel.SelectedPartys.Add(item);
}
var removed_items = e.RemovedItems.Cast<Party>().ToList();
foreach (var item in removed_items)
{
ViewModel.SelectedPartys.Remove(item);
}
ViewModel.SelectedPartyChanged();
}我们需要将ListViews选择的项目保存在Db中，然后在ListView中恢复它们--预选的，要做到这一点，我相信我们需要通过编程来选择一个项目，我们如何做到这一点？
回答 2
Stack Overflow用户
回答已采纳
发布于 2022-11-16 09:11:22
由于无法绑定到SelectedItems，因此可能需要创建从ListView派生的控件
CustomListView.cs
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using Microsoft.UI.Xaml.Data;
using Windows.Foundation.Collections;
namespace ListViews;
public class CustomListView : ListView
{
public static readonly DependencyProperty SelectedItemsSourceProperty = DependencyProperty.Register(
nameof(SelectedItemsSource),
typeof(object),
typeof(CustomListView),
new PropertyMetadata(default, (d, e) =>
{
(d as CustomListView)?.UpdateSelectedItemsSource();
}));
public object SelectedItemsSource
{
get => (object)GetValue(SelectedItemsSourceProperty);
set => SetValue(SelectedItemsSourceProperty, value);
}
private CollectionViewSource? SelectedItemsSourceViewSource { get; set; }
private ICollectionView? SelectedItemsSourceView { get; set; }
private void UpdateSelectedItemsSource()
{
if (SelectedItemsSourceView is not null)
{
SelectedItemsSourceView.VectorChanged -= SelectedItemsSourceView_VectorChanged;
}
SelectedItemsSourceViewSource = new()
{
Source = SelectedItemsSource
};
SelectedItemsSourceView = SelectedItemsSourceViewSource.View;
SelectedItemsSourceView.VectorChanged += SelectedItemsSourceView_VectorChanged;
}
private void SelectedItemsSourceView_VectorChanged(IObservableVector<object> sender, IVectorChangedEventArgs @event)
{
switch (@event.CollectionChange)
{
case CollectionChange.Reset:
SelectedItems.Clear();
break;
case CollectionChange.ItemInserted:
if (SelectedItemsSourceView?.Count >= @event.Index)
{
SelectedItems.Add(SelectedItemsSourceView[(int)@event.Index]);
}
break;
case CollectionChange.ItemRemoved:
if (SelectedItemsSourceView?.Count >= @event.Index)
{
SelectedItems.Remove(SelectedItemsSourceView[(int)@event.Index]);
}
break;
case CollectionChange.ItemChanged:
break;
default:
break;
}
}
}像这样使用它：
MainPage.xaml
<local:CustomListView
ItemsSource="{x:Bind ViewModel.Items, Mode=OneWay}"
SelectedItemsSource="{x:Bind ViewModel.SelectedItems, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
SelectionMode="Multiple">
<ListView.ItemTemplate>
<DataTemplate x:DataType="local:Item">
<TextBlock Text="{x:Bind Id}" />
</DataTemplate>
</ListView.ItemTemplate>
</local:CustomListView>Stack Overflow用户
发布于 2022-11-16 11:57:11
在WinUI 3 ListView上有一个名为YourListView.SelectRange()的方法
它在xaml的ListView上是不可用的，所以我通过MVVM消息调用在后面的代码中调用它。
文件后面的视图代码
public CodeBehindConstructor()
{
this.InitializeComponent();
// Rx ListView Select items
WeakReferenceMessenger.Default.Register<Msg_ListView_SelectItems>(this, (r, msg) =>
{
SelectParty(msg.Start, msg.Length);
});
}
public void SelectParty(int start, uint length)
{
Debug.WriteLine($"SelectParty start {start} len {length}");
LV_Partys.SelectRange(new ItemIndexRange(start, length));
}The ViewModel
// Select 1st Party
WeakReferenceMessenger.Default.Send(new Msg_ListView_SelectItems { Start = 0, Length = 1});// Start is 0 based, Length isnt it starts at 1
// Select 2nd Party
WeakReferenceMessenger.Default.Send(new Msg_ListView_SelectItems { Start = 1, Length = 1 });Msg_ListView_SelectItems类
public class Msg_ListView_SelectItems
{
public int Start { get; set; }
public uint Length { get; set; }
}如果您的ListViews选择模式是Multiple或Extended，那么.SelectRange()将选择一个连续的许多项，因此您可以对不按顺序顺序的项目多次调用SelectRange。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/74456195
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