I have a ListView with about 700 entries (one Image per entry). The ListView works just fine in vertical scroll mode. But when I change it to Horizontal it crashes on the phone with an OutOfMemory Exception.
I change the scroll direction with code from Microsoft:
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
It seems like Lord Windows is trying to load the complete list at once when the Orienation is changed. Anyone else experience this issue, maybe even provide a solution?
By using StackPanel you loose virtualization. So all the 700 entries are in memory at once when you scroll the list. Use VirtualizingStackPanel or better, use GridView instead of ListView.
Related
I have a GridView that I use to display thousands of images/thumbnails (using data binding). I used ImplicitAnimations to add transitions, so that when the control is resized and the number of columns changes - every item smoothly goes into the new position after the resize.
Problem
This all works fine when the user is at the top of the GridView but becomes a problem the further the user scrolls. The further you scroll, the more items are moved around when the number of columns changes. More rows are added/removed, but the Scrollbar is kept on the same position/offset which causes previously visible items to go far away from the view - and the user gets lost.
What I tried so far...
I tried working around this issue by tracking the first visible item on every scroll change event and then scrolling to it on SizeChanged event. The problem of this solution, however, is that it's really rough. Animations are no longer noticable and the whole experience is laggy.
Is there any better solution to this problem?
Illustration of the problem
Video example
I have also made a video to better illustrate the issue.
(The images have been blurred because some were NSFW)
Video Link
What I am looking for is a way for the scrollbar to adjust it's position on resize and stay on the same items the User was looking at - without messing up the animations.
Edit
So apparently this can't be solved any other way but manually scrolling to the item I wish to have visible on resize, which I already tried doing and had problems with the animations being really rough again because the ScrollToItem was happening AFTER the animations were being triggered.
So my question now is - can I scroll to an item on reorder/resize - BEFORE the animations get triggered? That way I think I could keep the smoothness. Using the resize event, however, doesn't work for this.
Edit 2 - Code sample
<GridView x:Name="mylist" animations:ReorderGridAnimation.Duration="600" ItemsSource="{Binding Source={StaticResource viewSource}}">
<GridView.ItemsPanel>
<ItemsPanelTemplate>
<ItemsWrapGrid Orientation="Horizontal" HorizontalAlignment="Center" Loaded="ItemsWrapGrid_Loaded"/>
</ItemsPanelTemplate>
</GridView.ItemsPanel>
<GridView.ItemTemplate>
<DataTemplate>
<Grid Width="300" Height="300" Background="Gainsboro">
<Image Source="{Binding ThumbnailImage}" />
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
GridView ItemSource is binded to the following CollectionView
<UserControl.Resources>
<controls:AdvancedCollectionView x:Key="viewSource" Source="{x:Bind Collection}" />
</UserControl.Resources>
I switched to the Community Toolkit for the animations and the AdvancedCollectionView. The custom panel is being used for 2 reasons - to get the Panel and apply implicit animations to it - and to keep the scrollbar on the rightmost side when HorizontalAlignment is Center.
The CollectionView is binded to an ObservableCollection.
To reproduce the issue - just add a lot of items into the ItemSource and try resizing the GridView at different scroll offsets (check video sample)
.
For your this issue, it may be caused by the ListView and GridView UI virtualization, you can try to use VariableSizedWrapGrid as the GridView's ItemsPanel,
<GridView>
<GridView.ItemsPanel>
<ItemsPanelTemplate>
<VariableSizedWrapGrid/>
</ItemsPanelTemplate>
</GridView.ItemsPanel>
</GridView>
But it will cost much device memory and performance without virtualization. So you should also take into consideration displaying many images in once.
As for displaying the Item that the User is looking at, since there are many items displayed in the screen, the GridView does not know to track witch one.So also as #Pratyay's suggestion, you need to keep track of the item then make the ScrollView witch is in the GridView to scroll to the item.
For example we have a ListBox with a UnidormGrid like a ListBoxPanel.
<ListBox>
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<UniformGrid Columns="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ListBox}, Path=Items.Count}"></UniformGrid>
<!--<cntr:StackGrid Orientation="Horizontal" Direction="Normal"/>-->
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<Button>1</Button>
<Button>2</Button>
<Button>3</Button>
<Button>4</Button>
</ListBox>
ListBox will give a infinite size to UniformGrid, but there is no any errors. UniformGrid will use only a visible size. How it do that? It will help me in bulding my own panel.
P.S. I know, that i can to disable ScrollView in ListBox and my panel will get a visible size.
As far as I know, the UniformGrid derives its cell size by the largest child it is displaying. It breaks the content to a new line when either its width or height is exceeded, according to the Orientation property. By default, it is set to Horizontal.
Which leads me to your question: why do you think that it has an infinite width? Sure, the ListBox contains a ScrollViewer in its default control template, but in my opinion it only provides vertical infinite space for the panel (horizontally, it is constrained to the width of the list box), which allows breaks for the default uniform grid to happen.
If you have any further questions, please feel free to ask.
I want to make calendar in windows phone 8 using XAML/c#. It should like horizontal bar that has 7 days fit to screen. User can scroll these dates like on phone screen there are 1 to 7 dates and user can scroll to view more dates. If user tap on any date then its color should be changed. I was trying to implement longlistselector and listbox but could do successfully. I am newbie. please help.
Thanks
ongListSelector doesn't allows you to change scroll orientation. In other controls like the ListBox you can specify the property ItemsPanel to use a StackPanel with horizontal orientation. But that property is not available in LongListSelector (i don't know exactly the reason, but i think it might be something related with the complex grouping, jump list capabilities of the LongListSelector.
If you need to make an horizontal list and you don't need to group your data, you can replace the LongListSelector with a ListBox and use the ItemsPanel property to specify a horizontal stackpanel.
So, no issues.
You can of course use the ListBox instead of LongListSelector.
You can have it horizontally scrollable as follows:
<ListBox ScrollViewer.HorizontalScrollBarVisibility="Auto">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Your control... />
</DataTemplate>
</ListBox.ItemTemplate>
I am a PHP developer learning c#, im starting with making a bingo game in c# using wpf.
At the moment, I need to make the number grid, so a grid of squares with the numbers 1-90 in them.
At the moment, I have a window MainGame, and I am using items from the toolbox, such grid, but cant work out an easy way to get 90 of the aligned nicely without having lots of tedious work. ONly way I know how is to drag 90 rectangles onto the window, but this is far from efficient.
What is the best way to approach this problem?
why not simply create a collection of numbers and put this as itemssource to an itemscontrol?
public List<int> MySquares {get;set;} //todo: initialize with your numbers 1-90
xaml
<ItemsControl ItemsSource="{Binding MySquares}">
you can choose an ItemsPanel(eg. WrapPanel) from your choice for alignment and create an ItemTemplate for your numbers
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
I have a layout where there are two listboxes, I was trying to make them sync and found some tutorials on the net like http://www.software-architects.com/TechnicalArticles/ScrollSync/tabid/101/Default.aspx or Listboxes, scrolling in sync but they dont seem to work under WP7 SDK because there are missing events or properties. Does anybody out there solved the problem of syncing two or more listboxes under windows phone 7?
Thanks in advance
See my answer in this question: WP7 ScrollViewer programatically scroll a background ScrollViewer in sync with front ScrollViewer
You will be able to keep the scrollviewers in sync, but it may not be smooth, as the WP7 scroll viewer does not have a Scroll event.
To get the ScrollViewer's generated by the ListBox's, use this solution by ColinE WP7 - Scrolling ListBox in external ScrollViewer.
I came up with a solution using the WarpPanel available from the Silverlight Toolkit for Wp7
<ListBox Height="350" HorizontalAlignment="Left" Margin="102,72,0,0" Name="lsScore" VerticalAlignment="Top" Width="450" HorizontalContentAlignment="Center">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<toolkit:WrapPanel ItemWidth="220" ItemHeight="50"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
This solution uses one listbox which is ofc always on sync and in order to seperate the data and align them I use the ItemWidth thats why it has such a high value. If you know any other way to seperate the data without using the ItemWidth property feel free to add an answer. Thanks in advance.