DataTemplate.LoadContent Método

Definición

Espacio de nombres:

Windows.UI.Xaml

Crea los objetos UIElement en DataTemplate.

public:
 virtual DependencyObject ^ LoadContent() = LoadContent;

DependencyObject LoadContent();

public DependencyObject LoadContent();

function loadContent()

Public Function LoadContent () As DependencyObject

Devoluciones

DependencyObject

UiElement raíz de DataTemplate.

Ejemplos

En los ejemplos siguientes se muestra el uso del método LoadContent para cambiar la apariencia de un borde en tiempo de ejecución. En el ejemplo se crea un ListBox que contiene los números del 1 al 10. Cuando el usuario selecciona un elemento en listBox, el borde muestra el número seleccionado. Si el usuario selecciona un número par, el número es rojo y tiene un círculo verde alrededor de él. Si el usuario selecciona un número impar, el número es azul y tiene un cuadrado púrpura alrededor de él.

<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

Comentarios

Cuando se llama a LoadContent, se crean los objetos UIElement de DataTemplate y se pueden agregar al árbol visual de otro UIElement.