DataTemplate.LoadContent Methode

Definition

Namespace:

Windows.UI.Xaml

Erstellt die UIElement-Objekte in der DataTemplate.

public:
 virtual DependencyObject ^ LoadContent() = LoadContent;

DependencyObject LoadContent();

public DependencyObject LoadContent();

function loadContent()

Public Function LoadContent () As DependencyObject

Gibt zurück

DependencyObject

Das STAMM-UIElement der DataTemplate.

Beispiele

Die folgenden Beispiele veranschaulichen die Verwendung der LoadContent-Methode, um die Darstellung eines Rahmens zur Laufzeit zu ändern. Im Beispiel wird ein ListBox-Objekt erstellt, das die Zahlen 1 bis 10 enthält. Wenn der Benutzer ein Element im ListBox-Element auswählt, wird im Rahmen die ausgewählte Zahl angezeigt. Wenn der Benutzer eine gerade Zahl auswählt, ist die Zahl rot und hat einen grünen Kreis um sie herum. Wenn der Benutzer eine ungerade Zahl auswählt, ist die Zahl blau und hat ein violettes Quadrat um sie herum.

<StackPanel  Name="rootStackPanel">

  <StackPanel.Resources>
    <DataTemplate x:Key="oddNumberTemplate">
      <Grid>
        <Rectangle Stroke="Purple" StrokeThickness="4" />
        <TextBlock HorizontalAlignment="Center" 
                   VerticalAlignment="Center" 
                   FontSize="24" Foreground="Blue" 
                   FontWeight="Bold"/>
      </Grid>
    </DataTemplate>


    <DataTemplate x:Key="evenNumberTemplate">
      <Grid>
        <Ellipse Stroke="Green" StrokeThickness="4"/>
        <TextBlock HorizontalAlignment="Center" 
                   VerticalAlignment="Center" 
                   FontSize="24" Foreground="Red" 
                   FontWeight="Bold"  />
      </Grid>
    </DataTemplate>
  </StackPanel.Resources>

  <Border Name="selectedItemDisplay"
          Width="50" Height="50"/>

  <ListBox Name="numberList" SelectionChanged="ListBox_SelectionChanged">
    <ListBoxItem Content="1"/>
    <ListBoxItem Content="2"/>
    <ListBoxItem Content="3"/>
    <ListBoxItem Content="4"/>
    <ListBoxItem Content="5"/>
    <ListBoxItem Content="6"/>
    <ListBoxItem Content="7"/>
    <ListBoxItem Content="8"/>
    <ListBoxItem Content="9"/>
    <ListBoxItem Content="10"/>
  </ListBox>

</StackPanel>

private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    ListBoxItem lbi = ((sender as ListBox).SelectedItem as ListBoxItem);
    SelectDataTemplate(lbi.Content);
}

private void SelectDataTemplate(object value)
{
    string numberStr = value as string;

    if (numberStr != null)
    {
        int num;

        try
        {
            num = Convert.ToInt32(numberStr);
        }
        catch
        {
            return;
        }

        DataTemplate template;

        // Select one of the DataTemplate objects, based on the 
        // value of the selected item in the ComboBox.
        if (num % 2 != 0)
        {
            template = rootStackPanel.Resources["oddNumberTemplate"] as DataTemplate;
        }
        else
        {
            template = rootStackPanel.Resources["evenNumberTemplate"] as DataTemplate;
        }

        selectedItemDisplay.Child = template.LoadContent() as UIElement;
        TextBlock tb = FindVisualChild<TextBlock>(selectedItemDisplay);
        tb.Text = numberStr;
    }
}

private childItem FindVisualChild<childItem>(DependencyObject obj)
    where childItem : DependencyObject
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(obj, i);

        if (child != null && child is childItem)
        {
            return (childItem)child;
        }
        else
        {
            childItem childOfChild = FindVisualChild<childItem>(child);
            if (childOfChild != null)
                return childOfChild;
        }
    }
    return null;
}

Private Sub ListBox_SelectionChanged(ByVal sender As Object, ByVal e As SelectionChangedEventArgs)
    Dim lbi As ListBoxItem = CType(CType(sender, ListBox).SelectedItem, ListBoxItem)
    SelectDataTemplate(lbi.Content)

End Sub

Private Sub SelectDataTemplate(ByVal value As Object)
    Dim numberStr As String = CType(value, String)

    If Not numberStr Is Nothing Then
        Dim num As Integer

        Try
            num = Convert.ToInt32(numberStr)
        Catch
            Return
        End Try

        Dim template As DataTemplate


        ' Select one of the DataTemplate objects, based on the 
        ' value of the selected item in the ComboBox.
        If num Mod 2 <> 0 Then
            template = CType(rootStackPanel.Resources("oddNumberTemplate"), DataTemplate)
        Else
            template = CType(rootStackPanel.Resources("evenNumberTemplate"), DataTemplate)
        End If

        selectedItemDisplay.Child = CType(template.LoadContent(), UIElement)
        Dim tb As TextBlock = FindVisualChild(Of TextBlock)(selectedItemDisplay)
        tb.Text = numberStr

    End If
End Sub

Private Function FindVisualChild(Of childItem As DependencyObject) _
        (ByVal obj As DependencyObject) As childItem

    Dim i As Integer

    For i = 0 To VisualTreeHelper.GetChildrenCount(obj) - 1

        Dim child As DependencyObject = VisualTreeHelper.GetChild(obj, i)
        If ((Not child Is Nothing) And (TypeOf child Is childItem)) Then
            Return child
        End If

        Dim childOfChild As childItem = Me.FindVisualChild(Of childItem)(child)
        If (Not childOfChild Is Nothing) Then
            Return childOfChild
        End If

    Next i

    Return Nothing

End Function

Hinweise

Wenn Sie LoadContent aufrufen, werden die UIElement-Objekte in dataTemplate erstellt, und Sie können sie der visuellen Struktur eines anderen UIElement hinzufügen.