I'm trying to create a scrolling list of fairly large textblocks. I want there to be a vertical scrollbar to show them all, and if they overflow a certain size I want them to display an ellipsis. I actually have all this working pretty good.
I have the following Silverlight XAML:
<Grid x:Name="LayoutRoot" MaxWidth="500" MinWidth="100"
MaxHeight="500" MinHeight="100">
<Grid.DataContext>
<app:MainPageViewModel/>
</Grid.DataContext>
<ScrollViewer>
<ItemsControl ItemsSource="{Binding TextItems}" Margin="0,20,0,20">
<ItemsControl.ItemTemplate><DataTemplate>
<Border MaxHeight="175" Margin="0,0,0,18" CornerRadius="5">
<TextBlock Margin="2" TextTrimming="WordEllipsis"
TextWrapping="Wrap" Text="{Binding}"/>
</Border>
</DataTemplate></ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>
</Grid>
My problem is that this layout does not use UI virtualization, such as with a VirtualizingStackPanel. So it is pretty slow. What is the best way to get UI virtualization into this layout? I've tried about a half dozen different ways and nothing has worked out all that well.
I managed to get this working in a ListBox because it seems to support virtualization out of the box. However, I'd prefer to use ItemsControl as I don't want these things to be selectable, and I don't want the styling that comes along with a ListBox.
This in Silverlight 4.
There are a few things you need to do to make this work.
Set the ItemsPanelTemplate for
your ItemsControl to a
VirtualizingStackPanel.
Incorporate the ScrollViewer inside
a ControlTemplate for your
ItemsControl instead of just
wrapping it around the outside.
Make sure the ItemsControl has a fixed height so the layout system can work out how many items it needs to fill the viewport. (It looks like you are already doing this by putting the ItemsControl in a Grid - that will allow the layout system to determine the alloted height for the control)
Here's the simplest example I could come up with of this working:
<ItemsControl ItemsSource="{Binding TextItems}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.Template>
<ControlTemplate TargetType="ItemsControl">
<Border>
<ScrollViewer>
<ItemsPresenter/>
</ScrollViewer>
</Border>
</ControlTemplate>
</ItemsControl.Template>
</ItemsControl>
Related
I want to show a list of thumbnails, and allow the user to choose one. A ListBox seemed an obvious choice, setting the template to include the thumbnail and description.
The following code does this correctly...
<ListBox Margin="5"
Name="BackgroundsLb">
<ListBox.ItemTemplate>
<DataTemplate>
<Border Margin="5"
BorderBrush="Black"
BorderThickness="1">
<StackPanel Margin="5">
<Image Source="{Binding Path=Data, Converter={StaticResource BytesToImageVC}}"
Width="150"
HorizontalAlignment="Center" />
<TextBlock Text="{Binding Path=Description}"
HorizontalAlignment="Center" />
</StackPanel>
</Border>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
However, this displays the thumbnails vertically, one per row, as is normal for a ListBox. Given that the thumbnails are only 150 pixels wide, I would like to show them in something more like a grid, but (ideally) in a way so that the number of columns adapts to the size of the window.
I tried replacing the ListBox with an ItemsControl, adding in the following...
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Vertical" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
...and it displayed exactly how I wanted it, but the ItemsControl does not allow selection, so is no use for my purpose.
Is there a way to achieve a flexible, selectable display that fills the horizontal space, and breaks onto a new row according to the size of the window?
Thanks
You can use an ItemsPanelTemplate in a ListBox just the same as you are using one in the ItemsControl. The difference I think you're seeing is that ListBox uses scroll bars by default rather than wrapping the content. Basically the content is allowed to grow forever, so you never get the wrap. Instead you get a scrollbar. The good news is you can disable this behavior. The following should give you a horizontal wrap, where new rows are created as needed.
<ListBox ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
I would like to create a multi-column list of checkboxes, but here's the catch - as I resize the window I would like everything to scale accordingly, including text size. I've been trying to make use of a WrapPanel and ViewBox but can't get the XAML right. Are these controls the best option or should I be using a ListBox (note I don't need selection functionality or scrollbars)? Any suggestions or examples on how I could achieve this would be much appreciated. I'm using MVVM and the list will be data bound, if that makes a difference.
BTW since starting WPF I've been struggling to understand which controls size to their children and which size to their parent. Are there any good sites, cheat sheets, or whatever summarising the behaviour of each control?
If you have a variable number of child elements, you could put a UniformGrid into a ViewBox.
If the child elements have to be visualized by a DataTemplate, you would have to use an ItemsControl with the ItemsPanel property set to such a UniformGrid:
<Viewbox Stretch="Uniform">
<ItemsControl ItemsSource="{Binding Items}" Width="400" Height="200">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<UniformGrid Columns="4"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Background="AliceBlue">
<CheckBox Content="{Binding Label}" IsChecked="{Binding IsChecked}"
HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Viewbox>
I have ItemsControl with VirtualizingStackPanel as items panel like this:
<ItemsControl Style="{StaticResource ItemsControl}" Name="itemsControl"
Margin="0,100,0,0" HorizontalAlignment="Stretch" Height="80">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBox />
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
Style is following:
<Style x:Key="ItemsControl" TargetType="ItemsControl">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ItemsControl">
<ScrollViewer VerticalScrollBarVisibility="Hidden"
HorizontalScrollBarVisibility="Visible">
<ItemsPresenter />
</ScrollViewer>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I set a collection with 100.000 elements as ItemsSource and get really good performance. Everything is fine except of one thing. When I input text in one of the text boxes and then start to scroll I see that that text appears everywhere throughout the list!
I understand what the VirtualizingStackPanel does. It's continuously loading elements that become visible as we scroll. I understand some aspects of it's virtualizing technique but I have no idea how to understand this strange behavior. I failed to find good doc's on WPF/Silverlight virtualization, so, please, explain me what is going on
VirtualizingStackPanel does not actually continiously load elements. Instead, it re-uses the existing elements (controls) and simply replaces the DataContext behind them.
So if you have an VirtualizingStackPanel with 100,000 items, and only 10 are visible at a time, it usually renders about 14 items (extra items for a scroll buffer). When you scroll, the DataContext behind those 14 controls gets changed, but the actual controls themselves will never get replaced.
If you do something like enter Text in TextBox #1, and that TextBox.Text is not bound to anything, then the Text will always show up because the control is getting re-used. If you bind the TextBox.Text to a value, then the DataContext will change when you scroll which will replace the displayed Text.
Not sure how to turn off recycling directly in a VirtualizingStackPanel but this is the syntax in a ListBox. I would have posted as a comment but I wanted formatted code.
<ListBox VirtualizingStackPanel.VirtualizationMode="Standard" />
I have an ItemsControl in my user control with a scroll viewer around it for when it gets too big (Too big being content is larger than the viewable area of the UserControl). The problem is that the grid that it is all in just keeps expanding so that the scroll viewer never kicks in (unless I specify an exact height for the grid). See code below and thanks in advance.
<UserControl x:Class="BusinessObjectCreationWizard.View.TableSelectionPageView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<GroupBox FontWeight="Bold" Height="300px"
Header="Tables"
Padding="2">
<ScrollViewer>
<ItemsControl FontWeight="Normal"
ItemsSource="{Binding Path=AvailableTables}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding Path=DisplayName}"
IsChecked="{Binding Path=IsSelected}"
Margin="2,3.5" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>
</GroupBox>
</UserControl>
This user control is loaded here
<Border Background="White" Grid.Column="1" Grid.Row="0">
<HeaderedContentControl Content="{Binding Path=CurrentPage}"
Header="{Binding Path=CurrentPage.DisplayName}" />
</Border>
I would like to not specify the height.
If you remove the Height from your GroupBox (which, as far as I understand, is what you want to do), then it will fill its container, unless there's a panel upstream that imposes its own sizing rules.
I used this simplified version of your XAML. I removed the template and the binding, and hard-coded some items, to make this stand alone; those changes won't affect the way layout is done.
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<GroupBox FontWeight="Bold" Header="Tables" Padding="2">
<ScrollViewer>
<ItemsControl FontWeight="Normal">
<TextBlock>Foo</TextBlock>
<TextBlock>Bar</TextBlock>
<TextBlock>Baz</TextBlock>
</ItemsControl>
</ScrollViewer>
</GroupBox>
</Window>
Run it, and you'll see that the content does indeed size to fit the window, and the scrollbar only enables when the window gets too small to see all three items. I believe this is what you want.
So the problem is most likely one of the parent panels, one you're not showing in your sample XAML. The problem you describe could occur if your GroupBox appears inside a StackPanel:
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<StackPanel>
<GroupBox FontWeight="Bold" Header="Tables" Padding="2">
<ScrollViewer>
<ItemsControl FontWeight="Normal">
<TextBlock>Foo</TextBlock>
<TextBlock>Bar</TextBlock>
<TextBlock>Baz</TextBlock>
</ItemsControl>
</ScrollViewer>
</GroupBox>
</StackPanel>
</Window>
Now the GroupBox appears at the top of the Window, sized to exactly fit its contents. If you shrink the Window enough, the GroupBox will be cut off -- because it's sized to fit its content, not its container. This sounds like the problem you're describing.
The reason is that StackPanel asks its children what their ideal height is (based on their content), and uses that height. Without StackPanel (or something similar), the default is to respect the control's VerticalAlignment, and if that's set to the default value of Stretch, then the control is stretched to fill its parent. This means it won't be taller than its parent, which sounds like what you want.
Solution: remove the StackPanel (or whatever else is causing you problems) and use something else. Depending on what you're trying to accomplish, you might have better luck with a DockPanel or a Grid. Hard to tell without knowing more about your layout.
Edit: Okay, it looks like the problem is indeed the HeaderedContentControl parent -- but not directly. HeaderedContentControl isn't a panel, so it doesn't do any layout of its own (and its descendant, GroupBox, doesn't have this same problem). The problem is its default template -- which includes a StackPanel. The good news is, you're free to use a different template, let's say one with a DockPanel instead:
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<HeaderedContentControl>
<HeaderedContentControl.Style>
<Style TargetType="{x:Type HeaderedContentControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type HeaderedContentControl}">
<DockPanel>
<ContentPresenter ContentSource="Header" DockPanel.Dock="Top"/>
<ContentPresenter/>
</DockPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</HeaderedContentControl.Style>
<GroupBox FontWeight="Bold" Header="Tables" Padding="2">
<ScrollViewer>
<ItemsControl FontWeight="Normal">
<TextBlock>Foo</TextBlock>
<TextBlock>Bar</TextBlock>
<TextBlock>Baz</TextBlock>
</ItemsControl>
</ScrollViewer>
</GroupBox>
</HeaderedContentControl>
</Window>
If you leave off the <HeaderedContentControl.Style> part, this reproduces your problem; but with the style in place, it allows the GroupBox to fill its container, so the ScrollViewer will get a scrollbar when you want it to.
If the previous answer doesn't fix the problem, you could also try binding the Width, Height of your grid to the ActualWidth, ActualHeight of your parent UserControl. Something like:
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Class="WpfApplication.UserControl1"
x:Name="UserControl">
<Grid Height="{Binding ElementName=UserControl, Path=ActualHeight}"
Width="{Binding ElementName=UserControl, Path=ActualWidth}" />
In this case you aren't setting an explicit width and height but you are limiting the Grids width/height to the constraints of the UserControl it sits in.
I had the same issue, after reading this response I replaced all StackPanels with Grids in UserControl. It resolved the Scrollbar issue.
Try removing the grid entirely and setting the HorizontalAlignment and VerticalAlignment directly on the GroupBox. If a layoutpanel has only one child, it's often redundant... this migth be true in your case.
If that doesn't work... what's the parent of your grid control?
Why not just use a listbox instead of an itemscontrol, that has a built in scrollviewer.
They are different. If you do not want to have the items selectable, then don't use a ListBox. It is going to be heavier, and will also have the deselect a selection everytime the user clicks on an entry. Just put the ItemsControl in a ScrollViewer
I had the same problema with ListBox, it wasn't expanding and the scroll viewer didn't appear. I solved it as follows:
<UserControl x:Class="TesteView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid MaxHeight="710">
....
....
<StackPanel>
<ListBox MaxHeight="515"
ScrollViewer.HorizontalScrollBarVisibility="Hidden"
ScrollViewer.VerticalScrollBarVisibility="Auto"
ItemsSource="{Binding Path=Teste,Mode=TwoWay}">
....
....
</ListBox>
</StackPanel>
</Grid>
</UserControl>
This question is the same as this other unanswered question.
When the Expander is expanded the outer ListView grows to make space for the expanders contents, but when the Expander is then collapsed the view does not force the ListView to resize.
Reduced code, with notes after:
<!--<StackPanel>-->
<ItemsControl>
<!-- ParameterGroupView -->
<Border BorderBrush="Brown" BorderThickness="1" CornerRadius="4" Padding="4">
<ListView HorizontalContentAlignment="Stretch">
<Expander Header="Expander A" IsExpanded="False">
<ListView HorizontalContentAlignment="Stretch">
<!-- TextView -->
<TextBlock >Content A</TextBlock>
<TextBlock >Content B</TextBlock>
</ListView>
</Expander>
</ListView>
</Border>
</ItemsControl>
<!--</StackPanel>-->
I have the ParameterGroupView in a ItemsControl or StackPanel because there is actually many ParameterGroupView entries. Swapping to a StackPanel does not change the behaviour.
Removing the Boarder does not affect the behaviour, but having it helps show the behaviour with only a single ParameterGroupView.
There can be many Expander sections in the outer ListView, and the Expander can have many entities inside the inner ListView.
The outer ListView and Expander is to replace a TreeView, that was used to have a list of collapsible nodes, but the TreeView's internal use of grids, means the TextView items were squashed horizonatlly, the same as if you remove ether HorizontalContentAlignment="Stretch" attributes.
So if there is another way to wrap/wire all this up, I'll be also happy.
This is a problem because our TextView blocks are large and there are many Expanders.
Edit: TextView is used as the code is data-bound, and thus dynamically put together. So any replacement for ListView would need some form of ItemsSource
Found the solution, and it details where in the question already.
ItemControl accepts an ItemsSource and auto resizes. So replacing the two ListViews with ItemControls gets the nested collapsing.
But there is no scrolling, so wrapping the outer ItemControl with a ScrollViewer, reproduces the complete desired effect.
<ScrollViewer
VerticalScrollBarVisibility="Auto">
<ItemsControl>
<!-- ParameterGroupView -->
<Border
BorderBrush="Brown"
BorderThickness="1"
CornerRadius="4"
Padding="4"
Height="Auto">
<ItemsControl
HorizontalContentAlignment="Stretch">
<Expander
Header="Expander A"
IsExpanded="False">
<ItemsControl
HorizontalContentAlignment="Stretch">
<!-- TextView -->
<TextBlock>Content A</TextBlock>
<TextBlock>Content B</TextBlock>
</ItemsControl>
</Expander>
</ItemsControl>
</Border>
</ItemsControl>
</ScrollViewer>
I was testing with double Expanders in the Border and double Border sections.
The most obvious thing to do here is to put the expanders in a container other than a listview:
<Border BorderBrush="Brown" BorderThickness="1" CornerRadius="4" Padding="4">
<StackPanel>
<Expander Header="Expander A" IsExpanded="False">
<ListView HorizontalContentAlignment="Stretch" MinWidth="100">
<ListBox Name="listb"></ListBox>
<!-- TextView -->
<TextBlock >Content A</TextBlock>
<TextBlock>Content B</TextBlock>
</ListView>
</Expander>
</StackPanel>
</Border>
The container resizes around content just fine.
If you absolutely must have it in a ListView (which is possible) then I don't know of a way to get a ListView to resize easily once it's grown (beyond setting explicit sizes of the whole thing, which is clumsy and not useful). If thats the case then it's possible that you'll have to use a controllable listbox to display all the open expanders, or display the content in a different way (like in a popup, maybe?) if you want to be able to see it all at a glance.