问题
When there are more items in combobox,combobox will show the listpicker flyout. If I select first one and scroll down,more than one item will be shown as selected. But SelectedItem of ComboBox will be the one which i selected. I modified the style of ListPickerFlyout and turned off the virtualization of ListView. If I do so ListView wont retain the SelectedItem. Is this bug of ComboBox? Is there any solution for this issue
Here is style which i modified
<DataTemplate x:Key="ListPickerFlyoutPresenterContentTemplate" >
<ListView VirtualizingStackPanel.VirtualizationMode="Recycling" SelectionMode="Single" >
<!--<ListView.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel/>
</ItemsPanelTemplate>
</ListView.ItemsPanel>-->
<ListView.ItemContainerStyle>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ListViewItem">
<Border x:Name="OuterContainer" RenderTransformOrigin="0.5,0.5">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal" />
<VisualState x:Name="Pressed"/>
<VisualState x:Name="Disabled"/>
<VisualStateGroup.Transitions>
<VisualTransition From="Pressed" To="Normal" />
</VisualStateGroup.Transitions>
</VisualStateGroup>
<VisualStateGroup x:Name="SelectionStates">
<VisualState x:Name="Unselected" />
<VisualState x:Name="Selected">
<Storyboard>
<DoubleAnimation Storyboard.TargetName="CheckGlyph" Storyboard.TargetProperty="Opacity" Duration="0" To="1" />
<DoubleAnimation Storyboard.TargetName="SelectedCheckMark" Storyboard.TargetProperty="Opacity" Duration="0" To="1" />
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="contentPresenter" Storyboard.TargetProperty="Foreground" Duration="0">
<DiscreteObjectKeyFrame KeyTime="0" Value="Green" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentBorder" Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ListPickerFlyoutPresenterSelectedItemBackgroundThemeBrush}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="SelectedUnfocused">
<Storyboard>
<DoubleAnimation Storyboard.TargetName="CheckGlyph" Storyboard.TargetProperty="Opacity" Duration="0" To="1" />
<DoubleAnimation Storyboard.TargetName="SelectedCheckMark" Storyboard.TargetProperty="Opacity" Duration="0" To="1" />
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="contentPresenter" Storyboard.TargetProperty="Foreground" Duration="0">
<DiscreteObjectKeyFrame KeyTime="0" Value="Green" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentBorder" Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ListPickerFlyoutPresenterSelectedItemBackgroundThemeBrush}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="DataVirtualizationStates">
<VisualState x:Name="DataAvailable" />
<VisualState x:Name="DataPlaceholder">
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="MultiSelectStates">
<VisualState x:Name="NoMultiSelect" />
<VisualState x:Name="ListMultiSelect">
</VisualState>
<VisualState x:Name="GridMultiSelect" />
<VisualStateGroup.Transitions>
<VisualTransition From="ListMultiSelect" To="NoMultiSelect" GeneratedDuration="0:0:0.15" />
<VisualTransition From="NoMultiSelect" To="ListMultiSelect" GeneratedDuration="0:0:0.15" />
</VisualStateGroup.Transitions>
</VisualStateGroup>
<!--<VisualStateGroup x:Name="HighlightStates">
<VisualState x:Name="NoHighlight" />
<VisualState x:Name="Highlighted">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="contentPresenter" Storyboard.TargetProperty="Foreground" Duration="0">
<DiscreteObjectKeyFrame KeyTime="0" Value="Red" />
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentBorder" Storyboard.TargetProperty="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ListPickerFlyoutPresenterSelectedItemBackgroundThemeBrush}" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>-->
</VisualStateManager.VisualStateGroups>
<Grid>
<ContentPresenter x:Name="contentPresenter"
ContentTransitions="{TemplateBinding ContentTransitions}"
ContentTemplate="{TemplateBinding ContentTemplate}"
Content="{TemplateBinding Content}"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
Margin="{TemplateBinding Padding}"
Style="{ThemeResource FlyoutPickerListViewItemContentPresenterStyle}" />
<!--The 'Xg' text simulates the amount of space one line of text will occupy.
In the DataPlaceholder state, the Content is not loaded yet so we
approximate the size of the item using placeholder text.-->
<TextBlock x:Name="PlaceholderTextBlock"
Opacity="0"
Text="Xg"
Foreground="{x:Null}"
Margin="{TemplateBinding Padding}"
IsHitTestVisible="False"
AutomationProperties.AccessibilityView="Raw"/>
<Rectangle x:Name="PlaceholderRect"
Visibility="Collapsed"
Fill="{ThemeResource FlyoutBackgroundThemeBrush}"
IsHitTestVisible="False" />
</Grid>
</Border>
</Border>
</Border>
<Border x:Name="SelectedBorder"
IsHitTestVisible="False"
Opacity="0"
BorderBrush="{ThemeResource ListViewItemSelectedBackgroundThemeBrush}"
BorderThickness="{ThemeResource GridViewItemMultiselectBorderThickness}">
<Grid x:Name="SelectedCheckMark"
Opacity="0"
Height="34"
Width="34"
HorizontalAlignment="Right"
VerticalAlignment="Top">
<Path x:Name="SelectedEarmark" Data="M0,0 L40,0 L40,40 z"
Fill="{ThemeResource ListViewItemSelectedBackgroundThemeBrush}"
Stretch="Fill" />
<Path x:Name="SelectedGlyph"
Data="M0,123 L39,93 L124,164 L256,18 L295,49 L124,240 z"
Fill="{ThemeResource ListViewItemCheckThemeBrush}"
Height="14.5"
Stretch="Fill"
Width="17"
HorizontalAlignment="Right"
Margin="0,1,1,0"
VerticalAlignment="Top"
FlowDirection="LeftToRight" />
</Grid>
</Border>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ListView.ItemContainerStyle>
<ListView.Footer>
<Border Height="{ThemeResource ListPickerFlyoutFooterThemeHeight}" Width="1" />
</ListView.Footer>
</ListView>
</DataTemplate>
When i select some item it wont go to selected visual state,It actually goes to Highlighted visual state and when i off the virtualization previous Highlighted state wont be retained
回答1:
The problem is with the virtualization of listviewitems(its a bug in the control).
The solution to this is to set the CacheLength property of the listview's itemsstackpanel.
The code is:
<DataTemplate x:Key="ListPickerFlyoutPresenterContentTemplate">
<ListView ItemContainerStyle="{StaticResource ListPickerFlyoutPresenterItemStyle}">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<ItemsStackPanel CacheLength="10" />
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.Footer>
<Border Height="{ThemeResource ListPickerFlyoutFooterThemeHeight}"
Width="1" />
</ListView.Footer>
</ListView>
</DataTemplate>
The solution removes the selction highlight after sometime(few seconds) only after the item is realized.
Hope the solution is fine else you'll have to override the PrepareContainerForItemOverride of the listview
来源：https://stackoverflow.com/questions/34217063/windows-phone-8-1-combobox-shows-multiple-items-as-selected-when-number-of-items