我正在使用UserControl内部的sdl/Multiselect-ComboBox，默认情况下它已折叠。按下按钮后，UserControl可见性将设置为可见，因此应将所有内容加载到可视树中。如果可见性设置为“可见”，则按此顺序调用存储库控件。
1）静态MultiSelectComboBox（）
2）公共重写void OnApplyTemplate（）
3）依赖属性回叫。
事件按此顺序排列。每件事都按预期工作。
但是当可见性默认设置为折叠时。依赖属性在OnApplyTemplate之前被调用，这是可以理解的。问题出在回调之后。加载所有属性并绑定所需的所有事件。
private static void ItemsPropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
LoadComponents(dependencyObject, dependencyPropertyChangedEventArgs);
}
private static void LoadComponents(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
var control = dependencyObject as MultiSelectComboBox;
if (control?.MultiSelectComboBoxGrid != null && control?.ItemsSource != null)
{
control.ItemsCollectionViewSource = new CollectionViewSource
{
Source = control.ItemsSource
};
if (dependencyPropertyChangedEventArgs.NewValue is IList newItems && newItems.Count > 0)
{
control.UpdateSelectedItemsContainer(newItems);
}
if (control.SelectedItemsControl == null)
{
control.SelectedItemsControl = VisualTreeService.FindVisualChild<ItemsControl>(control.MultiSelectComboBoxGrid, PART_MultiSelectComboBox_SelectedItemsPanel_ItemsControl);
}
if (control.DropdownListBox == null)
{
if (control.DropdownMenu == null)
{
control.DropdownMenu = VisualTreeService.FindVisualChild<Popup>(control.MultiSelectComboBoxGrid, PART_MultiSelectComboBox_Dropdown);
}
if (control.DropdownMenu != null)
{
control.DetachedFilterPanel = VisualTreeService.FindVisualChild<StackPanel>(control.DropdownMenu.Child, PART_MultiSelectComboBox_Detached_FilterPanel);
if (control.DetachedFilterPanel != null)
{
control.DetachedFilterTextBox = VisualTreeService.FindVisualChild<TextBox>(control.DetachedFilterPanel, PART_MultiSelectComboBox_Detached_Filter_TextBox);
control.DetachedFilterAutoCompleteTextBox = VisualTreeService.FindVisualChild<TextBox>(control.DetachedFilterPanel, PART_MultiSelectComboBox_Detached_Filter_AutoComplete_TextBox);
}
control.DropdownListBox = VisualTreeService.FindVisualChild<ListBox>(control.DropdownMenu.Child, PART_MultiSelectComboBox_Dropdown_ListBox);
}
}
}
}
在我的场景中，这在OnApplyTemplate之前被调用，因此我创建了一个名为LoadComponent Function的函数，并且也从OnApplyTemplate中对其进行了调用。一切正常，除了以下内容始终为空，当我检查Visual Tree时，它甚至没有出现]
if (control.SelectedItemsControl == null) { control.SelectedItemsControl = VisualTreeService.FindVisualChild<ItemsControl>(control.MultiSelectComboBoxGrid, PART_MultiSelectComboBox_SelectedItemsPanel_ItemsControl); }我无法理解其背后的原因。这是此部分的Xaml
<DataTemplate x:Key="MultiSelectComboBox.SelectedItemsPanel.Template"> <Border Background="White" BorderBrush="{StaticResource MultiSelectComboBox.SelectedItemsPanel.Border}" BorderThickness="1"> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition Width="*"/> <ColumnDefinition Width="20"/> </Grid.ColumnDefinitions> <Border Grid.Column="0" Margin="1" Background="White" BorderThickness="0"> <sdl:ContentItemsControl x:Name="PART_MultiSelectComboBox_SelectedItemsPanel_ItemsControl" ItemContainerStyle="{StaticResource MultiSelectComboBox.SelectedItems.ItemContainer.Style}" Style="{StaticResource MultiSelectComboBox.SelectedItemsPanel.WrapableItemsSource.Style}"> <sdl:ContentItemsControl.Resources> <DataTemplate x:Key="MultiSelectComboBox.SelectedItems.ItemTemplate"> <TextBlock Text="{Binding}" Style="{DynamicResource MultiSelectComboBox.DefaultTextBlock.Style}" Margin="2,0" /> </DataTemplate> <DataTemplate x:Key="MultiSelectComboBox.SelectedItems.Searchable.ItemTemplate"> <StackPanel Orientation="Horizontal"> <TextBox x:Name="PART_MultiSelectComboBox_SelectedItemsPanel_Filter_TextBox" IsEnabled="{Binding IsEditMode, RelativeSource={RelativeSource TemplatedParent}}" Focusable="True" IsTabStop="False" Margin="0" ForceCursor="True" BorderThickness="0" BorderBrush="Transparent" Padding="1" TextWrapping="NoWrap"/> <TextBox x:Name="PART_MultiSelectComboBox_SelectedItemsPanel_Filter_AutoComplete_TextBox" IsReadOnly="True" Focusable="False" IsTabStop="False" Margin="-2,0,0,0" BorderThickness="0" BorderBrush="Transparent" Padding="-3,1,0,1" TextWrapping="NoWrap"/> </StackPanel> </DataTemplate> </sdl:ContentItemsControl.Resources> </sdl:ContentItemsControl> </Border> <Button x:Name="PART_MultiSelectComboBox_Dropdown_Button" Grid.Column="1" Style="{StaticResource MultiSelectComboBox.DropDown.Button.Style}" > <ContentControl> <ContentControl.Style> <Style TargetType="ContentControl"> <Setter Property="IsTabStop" Value="False"/> <Setter Property="ContentTemplate" Value="{StaticResource MultiSelectComboBox.SelectedItemsPanel.Readonly.Glyph.Template}"/> <Style.Triggers> <DataTrigger Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type sdl:MultiSelectComboBox}}, Path=IsEditMode}" Value="True"> <Setter Property="ContentTemplate" Value="{StaticResource MultiSelectComboBox.SelectedItemsPanel.EditMode.Glyph.Template}"/> </DataTrigger> </Style.Triggers> </Style> </ContentControl.Style> </ContentControl> </Button> </Grid> </Border> </DataTemplate> <Style x:Key="MultiSelectComboBox.Custom.Style" TargetType="{x:Type sdl:MultiSelectComboBox}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type sdl:MultiSelectComboBox}"> <Grid x:Name="PART_MultiSelectComboBox" MaxHeight="{TemplateBinding ActualHeight}" MaxWidth="{TemplateBinding ActualWidth}" Style="{StaticResource MultiSelectComboBox.Style}"> <ToggleButton KeyboardNavigation.TabNavigation="None" IsChecked="{Binding Path=IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" IsTabStop="False"> <ToggleButton.Template> <ControlTemplate TargetType="ToggleButton"> <ContentControl ContentTemplate="{StaticResource MultiSelectComboBox.SelectedItemsPanel.Template}"/> </ControlTemplate> </ToggleButton.Template> </ToggleButton> <Popup x:Name="PART_MultiSelectComboBox_Dropdown" Margin="2" Grid.ColumnSpan="2" MaxHeight="{Binding Path=MaxDropDownHeight, RelativeSource={RelativeSource TemplatedParent} }" PlacementTarget="{Binding ElementName=PART_MultiSelectComboBox}" IsOpen="{Binding Path=IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" MaxWidth="{TemplateBinding ActualWidth}" Placement="Bottom" AllowsTransparency="True" PopupAnimation="Slide"> <themes:SystemDropShadowChrome x:Name="shadow" Color="Transparent" MinWidth="{Binding ActualWidth, ElementName=PART_MultiSelectComboBox}"> <Border x:Name="dropDownBorder" Margin="0,1,0,0" BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" BorderThickness="0" Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"> <Grid> <Grid.RowDefinitions> <RowDefinition Height="Auto"/> <RowDefinition Height="*"/> </Grid.RowDefinitions> <Grid Grid.Row="0" Visibility="{Binding DetachAutoCompleteFilterBox, RelativeSource={RelativeSource TemplatedParent},Converter={StaticResource BoolToVis},FallbackValue=Collpased}"> <Border BorderBrush="LightBlue" BorderThickness="1"> <Border.Effect> <DropShadowEffect ShadowDepth="0" Color="LightBlue" Opacity="1" BlurRadius="10"/> </Border.Effect> </Border> <Border Padding="2"> <StackPanel x:Name="PART_MultiSelectComboBox_Detached_FilterPanel" Orientation="Horizontal" Height="30"> <TextBox x:Name="PART_MultiSelectComboBox_Detached_Filter_TextBox" Margin="1,0,0,0" IsEnabled="{Binding IsEditMode, RelativeSource={RelativeSource TemplatedParent}}" Focusable="True" IsTabStop="False" ForceCursor="True" BorderThickness="0" BorderBrush="Transparent" Padding="1" TextWrapping="NoWrap"/> <TextBox x:Name="PART_MultiSelectComboBox_Detached_Filter_AutoComplete_TextBox" IsReadOnly="True" Focusable="False" IsTabStop="False" Margin="-2,0,0,0" BorderThickness="0" BorderBrush="Transparent" Padding="-3,1,0,1" TextWrapping="NoWrap"/> </StackPanel> </Border> </Grid> <Grid x:Name="grid" Grid.Row="1" RenderOptions.ClearTypeHint="Enabled" Visibility="{Binding Path=IsLoadingSuggestions, RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource ResourceKey=InvBoolToVis}}" > <Grid Visibility="{Binding Path=IsLoadingSuggestions, RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource ResourceKey=InvBoolToVis}}"> <Canvas x:Name="canvas" HorizontalAlignment="Left" Height="0" VerticalAlignment="Top" Width="0"> <Rectangle x:Name="opaqueRect" Fill="{Binding Background, ElementName=dropDownBorder}" Height="{Binding ActualHeight, ElementName=dropDownBorder}" Width="{Binding ActualWidth, ElementName=dropDownBorder}"/> </Canvas> <sdl:ExtendedListBox x:Name="PART_MultiSelectComboBox_Dropdown_ListBox" Style="{StaticResource MultiSelectComboBox.Dropdown.ListBox.Style}"> <sdl:ExtendedListBox.GroupStyle> <GroupStyle HeaderTemplate="{StaticResource MultiSelectComboBox.Dropdown.ListBox.Header.Template}"/> </sdl:ExtendedListBox.GroupStyle> <sdl:ExtendedListBox.Resources> <DataTemplate x:Key="MultiSelectComboBox.Dropdown.ListBox.ItemTemplate"> <TextBlock Text="{Binding}" Style="{StaticResource MultiSelectComboBox.DefaultTextBlock.Style}" Margin="2,2,2,3"/> </DataTemplate> </sdl:ExtendedListBox.Resources> </sdl:ExtendedListBox> </Grid> <ContentPresenter ContentSource="LoadingSuggestionsContent" Visibility="{Binding Path=IsLoadingSuggestions, RelativeSource={RelativeSource Mode=TemplatedParent}, Converter={StaticResource ResourceKey=BoolToVis}}"/> </Grid> </Grid> </Border> </themes:SystemDropShadowChrome> </Popup> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style>我浪费我的时间试图思考可能的原因，但无法使它正常工作。
我在UserControl中使用的是sdl / Multiselect-ComboBox，默认情况下它已折叠。按下按钮后，UserControl Visibility设置为可见，因此应将所有内容加载到...
我没有检查代码，但是行为的属性也有类似的问题。