I have the following ListBox:
<ScrollViewer>
<!--Spec Definitions-->
<ListBox DataContext="{Binding SpecPackageSpecGroupListViewModel}"
VirtualizingStackPanel.IsVirtualizing="True"
VirtualizingStackPanel.VirtualizationMode="Recycling"
ScrollViewer.IsDeferredScrollingEnabled="True"
ItemContainerStyle="{StaticResource SpecPackageSpecGroupListBoxStyle}"
ItemsSource="{Binding SortedChildren}"
Background="Transparent"
BorderThickness="0" SelectionMode="Extended"
Margin="5,5,5,5">
<ListBox.ItemTemplate>
<DataTemplate>
<Controls:SpecPackageSpecGroupControl/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</ScrollViewer>
This list box is supposed to host ~1000 items, but complex ones.
I want it to work with the VirtualizingStackPanel, so I have set the visualizing XAML configuration to:
VirtualizingStackPanel.IsVirtualizing="True"
VirtualizingStackPanel.VirtualizationMode="Recycling"
My problem is that I think it doesn't work - first - it takes a very long time to load ~700 items, and secondly, when I hit a breakpoint on my control constructor - I can see it is called 700 times:
public static int Counter = 0;
public SpecPackageSpecGroupControl()
{
InitializeComponent();
Counter++;
if (Counter%100 == 0)
Console.WriteLine("Hi");
}
I break point on the Console.WriteLine("Hi") and I can see that the static counter reached 700.
So basically the UIElements are being created although this is a virtual mode.
Am I misunderstanding the virtualization mode, or is there something I'm doing wrong?
Don't put it in a ScrollViewer. The XAML as you pasted indeed bypasses virtualization but for a different reason: the ListBox extends fully (without scrolling) because the scrollViewer allows it to. Because it is fully 'extended', the ListBox doesn't use virtualization. It will use its built-in scroll viewer if you place it in a regular container - Border, Grid etc.
Related
I was solving Windows Phone 8.1 ListView wobbling problem and had code like below, however, once I add the ItemTemplate, the contents of the List cannot be seen, I'm wondering why and how to fix the problem.
<ListView
Grid.Row="1"
x:Name="ListViewEvents"
Loaded="OnListViewEventsLoaded"
ItemsSource="{Binding xx}"
ItemTemplateSelector="{StaticResource xx}"
ItemContainerStyle="{StaticResource xx}"
IsItemClickEnabled="True">
<ListView.ItemTemplate >
<DataTemplate >
<Grid Width="{Binding ActualWidth, ElementName=EventsListGrid}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Your Width binding is trying to read the ActualWidth property of an element in your XAML named EventsListGrid, but there's no such element in the sample code you've provided. As such, the binding engine is unable to set the Width property on your grid, most likely setting it to some unset/NaN value. At least I can confirm this when setting up a similar case as the one you provided and inspecting in Snoop the ListViewItem containers generated for each item in the test collection bound to the ListView. Perhaps you want to set the element name to ListViewEvents in this case or some other parent element not shown in the example?
I am using an ItemsControl for showing alist of items and itrs xaml is like
<ItemsControl ItemsSource="{Binding ShelfItemsCollection}" Name="shelfGridView" Margin="5" >
<ItemsControl.ItemTemplate>
<DataTemplate>
<Stackpanel>
<Image Width="150" Height="200" Stretch="Fill" Source="{Binding CoverImage}" ></Image>
+
some other infos
</Stackpanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
The problem i am facing is i had almost 100 items in list and i am doing some filtering operations on the list based on some properties and limit the results to a lesser no ( say 20 items at a time)for doing this filtering it took a lot of time to refresh and load the list view .
This is the code i used for filtering
ICollectionView dataView = CollectionViewSource.GetDefaultView(shelfGridView.ItemsSource);
dataView.Filter = CloudFilter;
dataView.Refresh();
private bool CloudFilter(object item)
{
MyObject lib = item as MyObject;
return lib.Property !=valuetofilter;
}
Is any way to improve the perfomance or any specific reason for slow rendering ?
ItemsControl doesn't support UI virtualization out of the box. Either use ListBox or make ItemsControl UI virtualized.
You can enable UI virtualization on ItemsControl by following some steps :
Set VirtualizingStackPanel.IsVirtualizing="True" on ItemsControl.
Set ItemsPanel to be VirtualizingStackPanel.
Override ControlTemplate of ItemsControl and wrap ItemsPresenter inside ScrollViewer.
Set ScrollViewer.CanContentScroll="True" on ItemsControl.
Details for the above proposal can be found here.
Moreover, you are setting ItemsSource directly to SourceCollection i.e. ShelfItemsCollection and later filtering it by getting defualtView created underneath for that collection. Binding directly with sourceCollection will force ItemsControl(non-Virtualized ofcourse) to generate 100 containers to host your underlying objects.
Instead you should create ICollectionView with filter predicate set on it and bind ItemsSource to that instance. May be you can also create CollectionViewSource and bind with it. If you bind with filtered instance, it will generate only 20 containers (non-virtualized ItemsControl).
Ofcourse, enabling UI virtualization on ItemsControl, will generate containers for only visible UI items on GUI.
I'm trying to figure out how to make my ContentControl to correctly scroll Horizontally (Vertically its fine at the moment). By correctly i mean i would like to see the content to stretch (expand infinitely) while having minimum sizes to which a scrollbar would appear in order for the content not to overflow behind the ContentControl's area, so here's a quick introduction:
The main window is structured in this way:
Grid (2 columns of .3* and .7*)
Border
Grid (7 rows, one set to * where ContentControl is)
ScrollViewer with StackPanel (purely for test) wrapping a ContentControl that has Auto Width
ContentControl's Template:
Grid (Width set to UserControl's ActualWidth, 6 rows with one set to Auto where ItemsControl go
ItemsControl that describes an ItemTemplate of a type DataTemplate which contains a Grid inside of which i have a DataGrid
The actual problem is that the ContentControl grows as you resize the window, but does not shrink with window resize.
Main View XAML (truncated for clarity):
<ScrollViewer Grid.Row="5" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto">
<ContentControl Grid.Row="5" Background="Transparent" Focusable="False" Margin="0,5,0,0"
Content="{Binding CurrentSection}" ContentTemplateSelector="{StaticResource templateSelector}/>
</ScrollViewer>
Tempate XAML (truncated for clarity):
<Grid>
...
<ItemsControl Grid.Row="4" ItemsSource="{Binding Data.QualifyingDistributionsDividends}" x:Name="QualifyingItemsControl">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid x:Name="DTLayoutGrid">
...
<Grid Grid.Row="1" x:Name="DataLayout" Width="{Binding ElementName=DTLayoutGrid, Path=ActualWidth}" HorizontalAlignment="Stretch">
...
<DataGrid Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="8" HorizontalScrollBarVisibility="Disabled"
ItemsSource="{Binding Payments}" Style="{StaticResource DataGridStyle}" CellStyle="{StaticResource DataGridNormalCellStyle}">
</DataGrid>
</Grid>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
So what happens? Datagrid assumes width of the entire DataTemplate (well its underlying controls that are set to be DataTemplates size, then * column assumes all empty space. When you try to resize the entire window that holds this code it will grow correctly, expanding the * column but it seems shrinking is not "registered" and it keeps the size you expanded it to, applies a scrollbar over that and forgets about it.
What i've tried so far was to set widths for ItemsControl, its underlying parents like Grid etc, also setting size to ContentControl, StackPanel, ScrollViewer and parent Grid of that.
I've also tried using scrollviewers directly on the Datagrid which produces an epileptic "1 million resizes a second" scenario. I've also played around with HorizontalAlignments
Under certain situations i DID managed to get the horizontal scrollbar to appear correctly but unfortunately that makes my DataGrid's * column to assume Auto Width rather then Star so DataGrid starts having an empty area to the right (unacceptable unfortunately...)
I understand that in order for horizontal scrollbar to work the parent or child of the scrollviewer needs Width set, i guess i can't work out where exactly do i need to restrict it. DataGrids NEED to infinitely expand with the main window while having first column fill all the available space.
Do let me now if you need more information on this and I will gladly answer.
It seems to me that this is just another case of the dreaded StackPanel layout problem. This problem comes up again and again and I confess that I had the very same problem when I started learning WPF. The StackPanel does not take the available size of its parent into consideration whereas other Panels such as a DockPanel or a Grid (yes, that's actually a Panel too) do.
It's explained in the How to: Choose Between StackPanel and DockPanel page on MSDN:
Although you can use either DockPanel or StackPanel to stack child elements, the two controls do not always produce the same results. For example, the order that you place child elements can affect the size of child elements in a DockPanel but not in a StackPanel. This different behavior occurs because StackPanel measures in the direction of stacking at Double.PositiveInfinity; however, DockPanel measures only the available size.
The StackPanel should only really be used to align a number of items, such as Buttons or other controls in a straight line where available space is not a concern. So anyway, the solution should be simple... just remove the StackPanel from the ScrollViewer. It doesn't appear to serve any purpose there anyway.
UPDATE >>>
After looking again, it seems as though you're saying that the problem is inside the DataTemplate, right? You might be able to fix that by setting the ItemsControl.HorizontalContentAlignment property to Stretch. That would ensure that each item remains within the boundary of the ItemsControl.
I'd also remove your Binding on the Grid.Width as you don't need it... a child Grid will take up the full space of a parent Grid by default. If these ideas don't work, just simplify your problem. Seriously, if you follow the advise in the linked page from the Help Center that I gave you in the comments, then you'll either fix the problem, or be able to come back here and provide a complete, but concise example that we could test.
I've found the behavior I was looking for by using a UniformGrid as the ItemsPanel, with its rows bound to the count of the ItemsSource model:
<ScrollViewer>
<ItemsControl ItemsSource="{Binding MyCollection}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<UniformGrid Rows="{Binding MyCollection.Count}" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
...
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>
As #Sheridan pointed out above, it seems the StackPanel is causing trouble. Also, credit to https://stackoverflow.com/a/23375262/385273 for pointing out the UniformGrid option.
I'm facing a performance issue with a crowded combobox (5000 items). Rendering of the drop down list is really slow (as if it was computing all items before showing any).
Do you have any trick to make this dropdown display lazy?
Xaml code:
<Grid x:Name="LayoutRoot">
<StackPanel Orientation="Horizontal" Width="200" Height="20">
<TextBlock>Test Combo </TextBlock>
<ComboBox x:Name="fooCombo" Margin="5,0,0,0"></ComboBox>
</StackPanel>
</Grid>
code behind:
public MainPage()
{
InitializeComponent();
List<string> li = new List<string>();
int Max = 5000;
for (int i = 0; i < Max; ++i)
li.Add("Item - " + i);
fooCombo.ItemsSource = li;
}
Well, there seems to be a bug in the Combobox UI virtualization, so an autocompletebox should be the way to go.
If you want an actual ComboBox (and not an AutoCompleteBox) that did this you could replace the ItemsTemplate with a VirtualizingStackPanel. In your example this would look like:
<ComboBox x:Name="fooCombo" Margin="5,0,0,0">
<ComboBox.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel></VirtualizingStackPanel>
</ItemsPanelTemplate>
</ComboBox.ItemsPanel>
</ComboBox>
As a guide though, I'd probably review your usage scenario to see whether or not a ComboBox is the correct control for you - since 5000 items seems like a mighty lot for a drop down list.
By the way, the slowness is expected behavior in Silverlight and not a bug.
Use the AutoCompleteBox instead, adjust the number of characters that need to be entered before a drop down list will be filled to limit how many drop down items are needed at any one time.
For this question, let us assume that we will want to show the face of the employee, title, department, and whether they like Piña coladas/getting caught in the rain.
Perhaps it might look something like the following:
http://www.edrawsoft.com/images/examples/Photo-Org-Chart-Full.png
Would you use a...
System.Windows.Control.UserControl?
FrameworkElement?
UIElement?
Canvas
Why? As always, thank you for your advise! I greatly appreciate it!
If I had to create a org chart control with advanced layout I would probably derive from Control, and create a "real" templated control in a similar manner as e.g. the TreeView control. This is probably the most advanced route to create a new control, but also the most powerful.
You may also be able to modify the control template of a TreeView, and make it grow downwards from the center instead of left and down from the upper left corner, but it will probably be difficult or impossible to customize the layout of the various levels as the TreeViewItem doesn't carry any extra information to describe the layout of a particular node.
In fact I did recently some experiments modifying the TreeView control template, but I stumbled upon something I didn't understand. Luckily I figured out what I did wrong, and you can see how it is possible to change the orientation of TreeView child items from vertical to horizontal in my question here on Stack Overflow.
I've seen a website that uses TreeViewItem and ControlTemplates, but I can't find it at the moment, I think it was on CodeProject.
Another idea I was playing with recently is use 2 usercontrols, itemcontrols and stackpanels.
Here's an example of a an OrgBar rectangle with text under it and it renders it's children in OrgGroup control by setting the ItemSource to it's children collection recursively. You can put the root orgbar on a canvas and play around with paths for the arrows. I tried to point out the basics but if you need more I can fill in the blanks.
Public Class OrgBarDataNode
Public Property BarColor as New SolidColorBrush(Colors.Red)
Public Property BarName As String
Public Property Children as New ObservableCollection(Of OrgBarDataNode)
End Class
Class MainPage
...
Public Sub Loaded
Dim Root as New OrgBarDataNode With {.BarName = "Root"}
Dim Child1 as New OrgBarDataNode With {.Barname = "Child1"}
Root.Children.Add(Child1)
LayoutRoot.Children.Add(Root)
End Sub
...
End Class
<UserControl x:Class="OrgBar">
<Grid>
<StackPanel ToolTipService.ToolTip="{Binding BarName}" Cursor="Hand">
<Rectangle Fill="{Binding BarColor}" Style="{StaticResource RecStyle}"/>
<TextBlock Text="{Binding BarName}" HorizontalAlignment="Center"
Margin="0,10,0,0" />
<local:OrgGroup Margin="0,20" HorizontalAlignment="Center"
DataContext="{Binding Children}" />
</StackPanel>
</Grid>
</UserControl>
<UserControl x:Class="OrgGroup">
<Grid>
<!-- this {Binding} to nothing means bind to DataContext}-->
<ItemsControl ItemsSource="{Binding}" >
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Center" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<local:OrgBar Style="{StaticResource OrgBarStyle}"
DataContext="{Binding}" />
<!-- this {Binding} refers to the the child node this time} -->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</UserControl>
That's essentially a tree structure, so like Paully suggested, I would start with a TreeView (Silverlight Toolkit) and customize the control template and treeview itself.