Question

我有一个包含许多项的DataGrid，我需要以编程方式滚动到SelectedItem。我在StackOverflow和Google上搜索过，似乎解决方案是ScrollIntoView，如下所示：

grid.ScrollIntoView(grid.SelectedItem)

向上或向下滚动DataGrid，直到所选项目处于焦点。但是，根据相对于所选项目的当前滚动位置，所选项目可能最终成为DataGrid的ScrollViewer中的最后一个可见项目。我希望所选项目将成为ScrollViewer中的第一个可见项目（假设DataGrid中有足够的行允许这样做）。所以我尝试了这个：

'FindVisualChild is a custom extension method that searches in the visual tree and returns 
'the first element of the specified type
Dim sv = grid.FindVisualChild(Of ScrollViewer)
If sv IsNot Nothing Then sv.ScrollToEnd()
grid.ScrollIntoView(grid.SelectedItem)

首先，我滚动到DataGrid的末尾，然后才滚动到SelectedItem，此时SelectedItem显示在DataGrid的顶部。

我的问题是滚动到DataGrid的末尾效果很好，但随后滚动到所选项目并不总是有效。

如何解决此问题，或者是否有其他替代策略可以滚动到顶部位置的特定记录？

Answer 1

你是在正确的轨道上，只是尝试使用集合视图而不是直接在数据网格上工作以满足这种需求。

这是一个工作示例，如果可能，所需项目始终显示为第一个选定项目，否则滚动查看器将滚动到结尾，并在其位置选择目标项目。

关键点是：

在业务方面使用CollectionView并在XAML控件上启用当前项同步（IsSynchronizedWithCurrentItem=true）
推迟“真实”目标滚动，以便允许“选择最后一项”被视觉执行（使用优先级较低的Dispatcher.BeginInvoke）

这是业务逻辑（这是从C＃到VB的自动转换）

Public Class Foo

    Public Property FooNumber As Integer
        Get
        End Get
        Set
        End Set
    End Property
End Class

Public Class MainWindow
    Inherits Window
    Implements INotifyPropertyChanged

    Private _myCollectionView As ICollectionView

    Public Sub New()
        MyBase.New
        DataContext = Me
        InitializeComponent
        MyCollection = New ObservableCollection(Of Foo)
        MyCollectionView = CollectionViewSource.GetDefaultView(MyCollection)
        Dim i As Integer = 0
        Do While (i < 50)
            MyCollection.Add(New Foo)
            i = (i + 1)
        Loop

    End Sub

    Public Property MyCollectionView As ICollectionView
        Get
            Return Me._myCollectionView
        End Get
        Set
            Me._myCollectionView = value
            Me.OnPropertyChanged("MyCollectionView")
        End Set
    End Property

    Private Property MyCollection As ObservableCollection(Of Foo)
        Get
        End Get
        Set
        End Set
    End Property

    Private Sub ButtonBase_OnClick(ByVal sender As Object, ByVal e As RoutedEventArgs)
        Dim targetNum As Integer = Convert.ToInt32(targetScroll.Text)
        Dim targetObj As Foo = Me.MyCollection.FirstOrDefault(() => {  }, (r.FooNumber = targetNum))

        'THIS IS WHERE THE MAGIC HAPPENS
        If (Not (targetObj) Is Nothing) Then
            'Move to the collection view to the last item
            Me.MyCollectionView.MoveCurrentToLast
            'Bring this last item into the view
            Dim current = Me.MyCollectionView.CurrentItem
            itemsContainer.ScrollIntoView(current)
            'This is the trick : Invoking the real target item select with a low priority allows previous visual change (scroll to the last item) to be executed
            Dispatcher.BeginInvoke(DispatcherPriority.ContextIdle, New Action(() => {  }, Me.ScrollToTarget(targetObj)))
        End If

    End Sub

    Private Sub ScrollToTarget(ByVal targetObj As Foo)
        Me.MyCollectionView.MoveCurrentTo(targetObj)
        itemsContainer.ScrollIntoView(targetObj)
    End Sub

    Public Event PropertyChanged As PropertyChangedEventHandler

    Protected Overridable Sub OnPropertyChanged(ByVal propertyName As String)
        If (Not (PropertyChanged) Is Nothing) Then
            PropertyChanged?.Invoke(Me, New PropertyChangedEventArgs(propertyName))
        End If

    End Sub
End Class

这就是xaml

 <Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition/>
        <ColumnDefinition/>
    </Grid.ColumnDefinitions>
    <DataGrid x:Name="itemsContainer" ItemsSource="{Binding MyCollectionView}" IsSynchronizedWithCurrentItem="True"  Margin="2" AutoGenerateColumns="False" >
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding FooNumber}"></DataGridTextColumn>
        </DataGrid.Columns>
    </DataGrid>

    <StackPanel Grid.Column="1">
        <TextBox x:Name="targetScroll" Text="2" Margin="2"></TextBox>
        <Button Content="Scroll To item" Click="ButtonBase_OnClick" Margin="2"></Button>
    </StackPanel>
</Grid>

Answer 2

this other question的已接受答案显示了获取此类网格的第一个/最后一个可见行的不同方法。您可以找到行的索引并直接在那里滚动或逐行向下滚动，直到第一个可见行匹配。

Answer 3

我用以下代码解决了这个问题：

public partial class MainWindow:Window
{
    private ObservableCollection<Product> products=new ObservableCollection<Product> ();

    public MainWindow()
    {
        InitializeComponent ();

        for (int i = 0;i < 50;i++)
        {
            Product p=new Product { Name="Product "+i.ToString () };
            products.Add (p);
        }

        lstProduct.ItemsSource=products;
    }

    private void lstProduct_SelectionChanged(object sender,SelectionChangedEventArgs e)
    {
        products.Move (lstProduct.SelectedIndex,0);
        lstProduct.ScrollIntoView (lstProduct.SelectedItem);
    }
}

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


<Grid>
    <ListBox Name="lstProduct" Margin="20" DisplayMemberPath="Name" SelectionChanged="lstProduct_SelectionChanged" />
</Grid>

滚动WPF DataGrid以在顶部显示所选项目

3 个答案: