ItemContainerGenerator.ContainerFromItem（）返回null而VirtualizingStackPanel.IsVirtualizing ="假"

问题描述

我面临着 VirtualizingStackPanel.IsVirtualizing =FALSE并没有解决我的问题。是否有任何人面临同样的问题？

的事情是我有一个自定义组合框，

 <风格的TargetType ={X：类型MultiSelectionComboBox}> 
< setter属性=VerticalContentAlignmentVALUE =中心/> 
< setter属性=ItemsPanel> 
< Setter.Value> 
< ItemsPanelTemplate> 
< StackPanel的方向=垂直
 VerticalAlignment =中心
的Horizo​​ntalAlignment =中心
 VirtualizingStackPanel.IsVirtualizing =FALSE/> 
< / ItemsPanelTemplate> 
< /Setter.Value> 
< /二传手> 
< setter属性=ItemTemplate中> 
< Setter.Value> 
<&DataTemplate的GT; 
< StackPanel的方向=横向X：NAME =ItemStackVirtualizingStackPanel.IsVirtualizing =FALSE> 
<复选框X：NAME =CheckBoxItem
命令={结合的SelectItem，的RelativeSource = {的RelativeSource AncestorType = {X：类型MultiSelectionComboBox}}}
 CommandParameter ={结合重点}
> 
< /复选框> 
< TextBlock的文本={结合DisplayText}>< / TextBlock的> 
< / StackPanel的> 
< / DataTemplate中> 
< /Setter.Value> 
< /二传手> 
< setter属性=模板> 
< Setter.Value> 
<的ControlTemplate的TargetType ={X：类型组合框}> 
<电网X：NAME =放置SnapsToDevicePixels =真> 
< Grid.ColumnDefinitions> 
< ColumnDefinition WIDTH =*/> 
< ColumnDefinition WIDTH =自动/> 
< /Grid.ColumnDefinitions> 
< BORDER了borderThickness =1BorderBrush =黑> 
<文本框IsReadOnly =真Grid.Column =0
文本={结合文字，UpdateSourceTrigger = PropertyChanged的，的RelativeSource = {的RelativeSource AncestorType = {X：类型MultiSelectionComboBox}}}> ; 
< /文本框> 
< /边框> 
将;弹出X：名称=PART_Popup
 Grid.Column =0
调焦=假
 Grid.ColumnSpan =2
 ISOPEN ={结合IsDropDownOpen，的RelativeSource = {的RelativeSource TemplatedParent}，模式=双向}
放置=底
 VerticalOffset = -  1
 PlacementTarget ={绑定的ElementName = LayoutRoot} > 
< Popup.Resources> 
<风格的TargetType ={X：类型滚动条}支持算法FMP ={StaticResource的{X：类型滚动条}}> 
< Style.Triggers> 
<触发属性=方向值=垂直> 
< setter属性=了borderThicknessVALUE =0/> 
< /触发> 
< /Style.Triggers> 
< /样式和GT; 
< /Popup.Resources> 
<的ScrollViewer X：NAME =DropDownScrollViewer
背景={S​​taticResource的背景}
 BorderBrush ={TemplateBinding BorderBrush}
了borderThickness ={TemplateBinding了borderThickness} 
了minWidth ={结合ActualWidth的，的ElementName = LayoutRoot}
了maxHeight ={TemplateBinding MaxDropDownHeight}> 
< ItemsPresenter KeyboardNavigation.DirectionalNavigation =含有/> 
< /&的ScrollViewer GT; 
< /弹出> 
<切换按钮IsEnabled ={结合IsEnabled，UpdateSourceTrigger = PropertyChanged的，的RelativeSource = {的RelativeSource AncestorType = {X：类型MultiSelectionComboBox}}}Grid.Column =1=器isChecked{结合IsDropDownOpen，模式=双向，的RelativeSource = {的RelativeSource TemplatedParent}}风格={StaticResource的ComboBoxToggleButton}/> 
< /网格和GT; 
< /控件模板> 
< /Setter.Value> 
< /二传手> 
< /样式和GT; 
< / ResourceDictionary的> 
  

，但我无法通过，

$ B获得里面的复选框参考
$ b

  this.ItemContainerGenerator.ContainerFromItem（this.Items [0]）作为ComboBoxItem; 
  

有什么建议吗？

什么其实我是想实现的是，

我想改变复选框这是一个不同的物件可以在运行时改变物业器isChecked。我不能用，由于我不能在这一点上改变整个项目的当前状态绑定做到这一点。所以基本上，一旦新MultiSelectionComboBox创建我想要做这样的事情，

 的foreach（对象this.Items项）
 {
 ComboBoxItem comboBoxItem = this.ItemContainerGenerator.ContainerFromItem（项目）为ComboBoxItem; 
如果（comboBoxItem == NULL）
继续; 
 FrameworkElement的元素= comboBoxItem.ContentTemplate.LoadContent（）作为FrameworkElement的; 
复选框复选框= element.FindName（CheckBoxItem）的复选框; 
 checkBox.IsChecked = this.SelectedItem.Contains（项目）; 
} 
  

解决方案

尝试执行 UpdateLayout请（）在 this.ItemContainerGenerator.ContainerFromItem（项目）

I'm facing a similar problem with this question however VirtualizingStackPanel.IsVirtualizing="False" didn't solve my problem. Is there anyone facing the same issue?

The thing is I have a custom combobox,

<Style TargetType="{x:Type MultiSelectionComboBox}"  >
    <Setter Property="VerticalContentAlignment" Value="Center"/>
    <Setter Property="ItemsPanel">
        <Setter.Value>
            <ItemsPanelTemplate>
                <StackPanel Orientation="Vertical"
                VerticalAlignment="Center"
                HorizontalAlignment="Center"
                VirtualizingStackPanel.IsVirtualizing="False"/>
            </ItemsPanelTemplate>
        </Setter.Value>
    </Setter>
    <Setter Property="ItemTemplate">
        <Setter.Value>
            <DataTemplate>
                <StackPanel Orientation="Horizontal" x:Name="ItemStack" VirtualizingStackPanel.IsVirtualizing="False">
                    <CheckBox x:Name="CheckBoxItem"
                        Command="{Binding SelectItem, RelativeSource={RelativeSource AncestorType={x:Type MultiSelectionComboBox}}}"
                        CommandParameter="{Binding Key}"
                              >
                    </CheckBox>
                    <TextBlock Text="{Binding DisplayText}"></TextBlock>
                </StackPanel>
            </DataTemplate>
        </Setter.Value>
    </Setter>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ComboBox}">
                <Grid x:Name="Placement" SnapsToDevicePixels="true">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="Auto"/>
                    </Grid.ColumnDefinitions>
                    <Border BorderThickness="1" BorderBrush="Black">
                        <TextBox IsReadOnly="True" Grid.Column="0" 
                                 Text="{Binding Text, UpdateSourceTrigger=PropertyChanged, RelativeSource={RelativeSource AncestorType={x:Type MultiSelectionComboBox}}}">
                        </TextBox>
                    </Border>
                    <Popup x:Name="PART_Popup" 
                               Grid.Column="0"
                               Focusable="False"
                               Grid.ColumnSpan="2"
                               IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}"
                               Placement="Bottom"
                               VerticalOffset="-1"
                               PlacementTarget="{Binding ElementName=LayoutRoot}">
                        <Popup.Resources>
                            <Style TargetType="{x:Type ScrollBar}" BasedOn="{StaticResource {x:Type ScrollBar}}">
                                <Style.Triggers>
                                    <Trigger Property="Orientation" Value="Vertical">
                                        <Setter Property="BorderThickness" Value="0"/>
                                    </Trigger>
                                </Style.Triggers>
                            </Style>
                        </Popup.Resources>
                        <ScrollViewer x:Name="DropDownScrollViewer"
                                          Background="{StaticResource Background}"
                                          BorderBrush="{TemplateBinding BorderBrush}"
                                          BorderThickness="{TemplateBinding BorderThickness}"
                                          MinWidth="{Binding ActualWidth, ElementName=LayoutRoot}"
                                          MaxHeight="{TemplateBinding MaxDropDownHeight}">
                            <ItemsPresenter KeyboardNavigation.DirectionalNavigation="Contained"/>
                        </ScrollViewer>
                    </Popup>
                    <ToggleButton IsEnabled="{Binding IsEnabled, UpdateSourceTrigger=PropertyChanged, RelativeSource={RelativeSource AncestorType={x:Type MultiSelectionComboBox}}}" Grid.Column="1" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Style="{StaticResource ComboBoxToggleButton}"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>
</ResourceDictionary>

and yet I can't get a reference to the checkbox inside via,

this.ItemContainerGenerator.ContainerFromItem(this.Items[0]) as ComboBoxItem;

Is there any suggestions?

What i actually want to achieve is,

i want to change checkboxes ischecked property which is depending on an other object which can change on runtime. I can't do it with using bindings due to the current state of the overall project which i can not change at this point. So basically once the new MultiSelectionComboBox is created i want to do something like this,

foreach (object item in this.Items)
{
    ComboBoxItem comboBoxItem = this.ItemContainerGenerator.ContainerFromItem(item) as ComboBoxItem;
    if (comboBoxItem == null)
        continue;
    FrameworkElement element = comboBoxItem.ContentTemplate.LoadContent() as FrameworkElement;
    CheckBox checkBox = element.FindName("CheckBoxItem") as CheckBox;
    checkBox.IsChecked = this.SelectedItem.Contains(item);
}

解决方案

try execute UpdateLayout() before this.ItemContainerGenerator.ContainerFromItem(item)

这篇关于ItemContainerGenerator.ContainerFromItem（）返回null而VirtualizingStackPanel.IsVirtualizing ="假"的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！