WPF wrappanel item alignment problem when scrolling

Question

Someone help me out pls.

I set a wrapPanel in a listbox itemPanelTemplate, Also, I already set the ScrollViewer.CanContentScroll="True".

But why the listbox items are not scrolling up/down by ITEM one by one? The scroll style is still by PIXEL.

Is anyone help me?

<Grid>
    <ListBox x:Name="testListbox" ScrollViewer.CanContentScroll="True">
        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <WrapPanel Width="200" ScrollViewer.CanContentScroll="True"/>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>


        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

        <ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
            <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/>
        </ListBoxItem>

    </ListBox>

</Grid>

Answer 1

Hi,

I think i may be able to help, although i'm not exactly sure what you are trying to achieve. Can you be more specific; are you trying to get each ListBoxItem to have scrolling ability - for its content?

Since you can't add a ScrollViewer to the ItemPanelTemplate, have you considered adding one to the individual ListBoxItems:

Example:

<ListBoxItem Background="LimeGreen" BorderBrush="Black" BorderThickness="3" ScrollViewer.CanContentScroll="True">
                <ScrollViewer>
                    <Image Height="50" Width="80" ScrollViewer.CanContentScroll="True"/> 
                </ScrollViewer>
            </ListBoxItem>

For more wpf/xaml help i found this site was quite good: www.YourCodeFactory.com

Answer 2

Thank codeB10.

I want to achieve the listbox scrolling ability that scroll image item by item. That mean I can scroll the listboxitem row by row instead of smoothly by pixel.

you can try to mark up the "ListBox.ItemsPanel" block in above code and try the scroll by item.

It's strange that listbox is not scrolling by item when I add the wrappanel block.

Answer 3

The wrappanel was not designed with this feature (logical scrolling) in mind. You will need to create a new panel object deriving from the wrappanel class and then implement the IScrollInfo interface in order to achieve the results that you're looking for.

Answer 4

Albert, Can you please provide sample code if you have any.. Which methods of IScrollInfo should I implement?