VirtualizingStackPanel bottom docking - wpf

I'm working on some chat application and using VirtualizingStackPanel. When my message list is scrolled down, I want it to be docked to the bottom of the container. But when I use virtualization there is always some whitespace, because panel docks top message, not the bottom. Here is an example: left is what I have and right is what I want.
Here is my markup.
<ItemsControl ItemsSource="{Binding Chat.MessagesList}">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type models:ChatMessage}">
...
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel VerticalAlignment="Bottom"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.Template>
<ControlTemplate>
<ScrollViewer CanContentScroll="True"
PanningMode="VerticalOnly"
VerticalScrollBarVisibility="Auto"
VirtualizingStackPanel.IsVirtualizing="True"
VerticalAlignment="Bottom"
VerticalContentAlignment ="Bottom">
<ItemsPresenter/>
</ScrollViewer>
</ControlTemplate>
</ItemsControl.Template>
</ItemsControl>
Is there any possibility to have messages aligned bottom and save virtualization? Any clue would be helpful.

Add
VirtualizingPanel.ScrollUnit="Pixel" VirtualizingPanel.IsContainerVirtualizable="True" to the ItemsControl.
Scrolling will be measured by pixels instead of items in the collection.

Related

How to identify when end of the list is reached on scrolling in scrollview

I am having the Scrollview as following. Now what my scenario is, Initially the scrollviewr will display 10 items. When the scrollbar reaches the 10th item I need some functionality to be implemented. Now the problem is I am unable to to recognize when the scrollbar is reaching the last item. I tried to use the ScrollChanged event with the vertical offsets but that seems to be not working. Is there any way to achieve this.
<ScrollViewer x:Name="ChatListScrollViewer" Background="#ffffff" Grid.Column="0" ScrollChanged="ChatListScrolled" Focusable="False">
<VirtualizingStackPanel VerticalAlignment="Stretch">
<ItemsControl VirtualizingStackPanel.VirtualizationMode="Recycling" Background="White" x:Name="MessageList" ItemsSource="{Binding Source={StaticResource ChatList}}" Focusable="False" BorderBrush="Transparent" BorderThickness="0" HorizontalAlignment="Stretch" ScrollViewer.HorizontalScrollBarVisibility="Hidden" x:FieldModifier="public">
<ItemsControl.GroupStyle>
<GroupStyle>
<GroupStyle.HeaderTemplate>
<DataTemplate>
<!-- Code -->
</DataTemplate>
</GroupStyle.HeaderTemplate>
</GroupStyle>
</ItemsControl.GroupStyle>
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0">
<!-- Code -->
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</VirtualizingStackPanel>
</ScrollViewer>
EDIT: The scrolling is from bottom to up for my scenario. This is How to find that ScrollViewer is scrolled to the end in WPF? useful to detect the last item of the when the scrolling is downwards.
In my scenario, its a like chat application. When the scrollbar is scrolled towards up, and reaches the last messages I need to have retrieve some more data .

User Controls Wrapped inside a panel MVVM

I am new to WPF/Xaml and searched for this issue I am facing but found it tough. Requesting some help on this.
I need to display usercontrols (DATABOUND) (horizontally) inside a panel/listview so that they wrap when the width of listview/panel is met, with a vertical scroll bar autoshown (as in figure).
so far I have this code.
<ListView Grid.Row="3"
ItemsSource="{Binding Controls}"
VerticalAlignment="Bottom" Background="{x:Null}" BorderBrush="{x:Null}"
>
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" Margin="0,0,0,10"></StackPanel>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="VerticalContentAlignment" Value="Bottom"/>
<Setter Property="Focusable" Value="False" />
</Style>
</ListView.ItemContainerStyle>
<!--<ListView.ItemTemplate>
<DataTemplate>
<ContentControl Content="{Binding}" VerticalContentAlignment="Bottom"/>
</DataTemplate>
</ListView.ItemTemplate>-->
</ListView>
I have even tried the below code. Yes, it wraps but no scrollbar appears!
<ItemsControl Grid.Row="3"
Width="100" Height="200"
ItemsSource="{Binding Controls}"
VerticalAlignment="Bottom" Background="{x:Null}" BorderBrush="{x:Null}"
>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" Margin="0,0,0,10"></WrapPanel>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
Note: I am okay with any control that makes this happens. Not necessarily be a listview.
To wrap items you need to set ItemsPanel to WrapPanel, like in second example, but you may need to disable horizontal scrolling on ListView:
<ListView ScrollViewer.HorizontalScrollBarVisibility="Disabled" .../>
also, if you want to use ItemsControl then ScrollViewer is not part of default Template, like for ListView, so you'll need to wrap in in ScrollViewer
<ScrollViewer Grid.Row="3">
<ItemsControl ...>
<!-- .... -->
</ItemsControl>
</ScrollViewer>
and don't forget to move Grid.Row="3" from ItemsControl definition to ScrollViewer
You were close :-)
Put your listview with a view panel that is a wrapanel inside your scrollviewer.
<ScrollViewer>
<ItemsSource="{Binding Controls}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel></WrapPanel>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
</ScrollViewer>
You are using Wrap panel so you need to specify the width it supposed to take... since wrappanel is inside a items host control wrap panel itself cannot calculate the width.It will try to take all the width with respective to Orientation (in your case its horizontal)
Here is the sample code with list box as items host... in this code i have binded the wrappanel width to the actual width of the list box so that it will never take more width than the list box and also i disabled the horizontal scrolling which you don't need for horizontal orientation and vertical wrapping
Note: Make sure to change item template before using following code and it will work with all items hosts like ListView, ItemsControl...
<ListBox Width="500" Height="500" Name="listbox" ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" Width="{Binding ActualWidth,ElementName=listbox}"></WrapPanel>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid Height="100" Width="100">
<TextBlock Text="{Binding}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
For ItemsControl
<ItemsControl Grid.Row="3"
Width="100" Height="200"
ItemsSource="{Binding Controls}"
VerticalAlignment="Bottom" Background="{x:Null}" BorderBrush="{x:Null}"
Name="listbox"
>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel IsItemsHost="True" Orientation="Horizontal" Width="{Binding ActualWidth,ElementName=listbox}"></WrapPanel>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.Template>
<ControlTemplate>
<ScrollViewer x:Name="ScrollViewer" Padding="{TemplateBinding Padding}">
<ItemsPresenter />
</ScrollViewer>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid Height="30" Width="30">
<TextBlock Text="{Binding}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>

WPF WrapPanel / ItemsControl not scrolling

I have a wrap panel displaying items but I cant get a scroll bar to work properly any idea's whats wrong ?
<ScrollViewer>
<ItemsControl Name="itemsControl">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel ItemWidth="{Binding ElementName=sizeSlider, Path=Value}"
FlowDirection="LeftToRight" Height="auto" Width="auto"
HorizontalAlignment="Left" Name="wrapPanel1"
VerticalAlignment="Top"
Margin="5"
>
</WrapPanel>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
</ScrollViewer>
</StackPanel>
Your ScrollViewer is inside StackPanel which resizes to its content (either vertically or horizontally depending on its orientation). Place it either directly in a Window, a cell of a Grid, or a DockPanel for scroll bars to show up.

Silverlight ItemsControl vertical scrollbar, using a wrappanel as ControlTemplate

I have a collection of elements, each one with a name and a subcollection of image blobs.
I want to display an Accordion, with each item representing each of the MainElements. inside each element, I display the images in the subcollecion of said MainElement.
The Accordion gets resized by the user, so I use a wrappanel for presenting the images. When the accordion is wide enough, the images reorder themselves fitting as many as posible in each row.
the problem comes when the wrappanel only displays one image per row (because there's no space enough for more), the image list continues, but I can't see all the images, because they don't fit inside the control's height.
I need a vertical scrollbar to be displayed inside the AccordionItem so I can scroll down the image list.
So, here's my code:
<layoutToolkit:Accordion Width="Auto" Height="Auto" ItemsSource="{Binding MainElementCollection}">
<layoutToolkit:Accordion.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding MainElementName}" />
</DataTemplate>
</layoutToolkit:Accordion.ItemTemplate>
<layoutToolkit:Accordion.ContentTemplate>
<DataTemplate>
<ItemsControl ItemsSource="{Binding SubElementCollection}" ScrollViewer.VerticalScrollBarVisibility="Auto" >
<ItemsControl.Template>
<ControlTemplate>
<controlsToolkit:WrapPanel />
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<Image Margin="2" Width="150" Source="{Binding PreviewImage, Converter={StaticResource ImageConverter}}" />
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</DataTemplate>
</layoutToolkit:Accordion.ContentTemplate>
</layoutToolkit:Accordion>
http://www.silverlightshow.net/tips/How-to-add-scrollbars-to-ItemsControl.aspx suggests that I should surround my wrappanel with a scrollviewer, like this
<ItemsControl.Template>
<ControlTemplate>
<scrollviewer>
<controlsToolkit:WrapPanel />
</scrollviewer>
</ControlTemplate>
</ItemsControl.Template>
But then my wrappanel gets really small and I can only see a small vertical scrollbar
Any ideas?
Thanks a lot.
Edit: I figured thatthe wrappanel loses its width when used in the controltemplate
It should be used as follows:
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<controlsToolkit:WrapPanel ScrollViewer.VerticalScrollBarVisibility="Visible" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
Anyway, I tried adding the ScrollViewer.VerticalScrollBarVisibility="Visible" line but I'm stuck again.
Edited again:
Now my wrappanel looks like this:
<ItemsControl ItemsSource="{Binding StageVideos}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<controlsToolkit:WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Image Margin="2" Width="150" Cursor="Hand" MouseLeftButtonDown="videoPreview_MouseLeftButtonDown" Tag="{Binding}" Source="{Binding PreviewImage, Converter={StaticResource ImageConverter}}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.Template>
<ControlTemplate>
<ScrollViewer VerticalScrollBarVisibility="Visible">
<ItemsPresenter />
</ScrollViewer>
</ControlTemplate>
</ItemsControl.Template>
</ItemsControl>
I'm using a wrappanel as the items panel, and I'm using the ControlTemplate to surround the presenter with a scrollviewer. Still, no luck :/
It's working perfectly. i had two different Accordions on the same page, and I was checking my code changes in the one whose code I wasn't touching.
Sometimes you need to pause, go for a walk and then look at the whole screen.
The right code is the last one:
<ItemsControl ItemsSource="{Binding StageVideos}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<controlsToolkit:WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Image Margin="2" Width="150" Cursor="Hand" MouseLeftButtonDown="videoPreview_MouseLeftButtonDown" Tag="{Binding}" Source="{Binding PreviewImage, Converter={StaticResource ImageConverter}}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.Template>
<ControlTemplate>
<ScrollViewer VerticalScrollBarVisibility="Visible">
<ItemsPresenter />
</ScrollViewer>
</ControlTemplate>
</ItemsControl.Template>
</ItemsControl>

WPF: ListBox with WrapPanel, vertical scrolling problem

I have a UserControl (XAML below) that has a ListBox that I want to display images inside a WrapPanel, where images are displayed as many as will fit on one row and then wrap onto the next row etc. It works, except when the ListBox grows higher than the available space in the window, I'm not getting a vertical scrollbar, i.e. the contents get clipped. If I set a fixed height on the ListBox, the scrollbar appears and works as expected. How can I get this listbox to grow to the available space and then show a vertical scrollbar? This control is inside StackPanel inside a Grid in the main window. If I wrap the StackPanel inside a ScrollViewer, I get the scrollbar I'm after, but that's not really a good solution if I wanted to add some more controls to the UserControl above the ListBox (e.g. image size "zoom" etc) as I wouldn't want them to scroll with the images.
Thanks!! :)
<UserControl x:Class="GalleryAdmin.UI.GalleryView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ListBox Name="itemListBox" BorderThickness="0" ItemsSource="{Binding}" ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Background="LightGray" Margin="5" >
<StackPanel Margin="5">
<Image Source="{Binding Path=LocalThumbPath}" Height="100" />
<TextBlock Text="{Binding Path=Name}" TextAlignment="Center"></TextBlock>
</StackPanel>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
I think you better go with override the ItemPanelTemplate:
<Grid>
<ListBox ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel IsItemsHost="True" />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBoxItem>listbox item 1</ListBoxItem>
<ListBoxItem>listbox item 2</ListBoxItem>
<ListBoxItem>listbox item 3</ListBoxItem>
<ListBoxItem>listbox item 4</ListBoxItem>
<ListBoxItem>listbox item 5</ListBoxItem>
</ListBox>
Well, I finally stumbled upon the solution. I was adding my UserControl to a placeholder panel that looked like this:
<ScrollViewer Margin="20" >
<StackPanel Name="contentPanel"></StackPanel>
</ScrollViewer>
However, when I switched it to a Grid instead, things started to work the way I wanted:
<Grid Name="contentPanel" Margin="20" />
I think it has to do with the StackPanel not taking up all the vertical space by default, like the Grid is doing.
All I had to do was set the following, and the problem went away:
<ListBox ScrollViewer.HorizontalScrollBarVisibility="Disabled">
I was just looking through several questions about this issue, and although this is an old thread, this one gave me the answer, but just to clarify....
The layout GRID is the answer to most issues like this. To get the proper ListBox/WrapPanel operation to fill the available space, the following code does the trick:
<Grid Grid.Row="1" MaxHeight="105">
<ListBox ItemTemplate="{DynamicResource StoreGroupTemplate01}" ItemsSource="{Binding StoreGroupHeader}"
ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
</Grid>
I have this in another grid to place the list at the bottom of my screen (ie.. the Grid.Row="1") and you can adjust MaxHeight (or remove it) to control the visible area before the vertical scroll bar will show up.
Put your listbox inside of a ScrollViewer and then set the scrollviewer's VerticalScrollBarVisibility property to "Auto"
<ScrollViewer VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Disabled">
<ListBox Name="itemListBox" BorderThickness="0" ItemsSource="{Binding}" >
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Background="LightGray" Margin="5" >
<StackPanel Margin="5">
<Image Source="{Binding Path=LocalThumbPath}" Height="100" />
<TextBlock Text="{Binding Path=Name}" TextAlignment="Center"></TextBlock>
</StackPanel>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
</ScrollViewer>
HTH

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