I have items coming from server dynamically and I need to create an ItemTemplate for those items.
I looked for ScrollViewer but I couldn't find ItemTemplate or ItemsSource property.
Is there a way to list items in phone:longListSelector horizontally?
You can inside your Scrollviewer use a Listbox like this;
<ScrollViewer>
<ListBox ItemsSource="your source" ItemTemplate="your template" />
</ScrollViewer>
Related
In the Universal Windows Platform API, how do I use x:Bind inside of a User Control (intended to be the layout for a GridView's ItemTemplate) to bind to instance properties of a GridView's ItemSource?
Background
I'm trying to re-create the layout found in Windows 10 stock apps like Sports, News, Money, etc.
I'm using a two GridViews for the main area of the app; one for "featured articles" (2 large photos w/ headlines) and one for all the other articles (smaller photos w/ headlines).
I'm able to bind to a data source that I supply in the code behind (a List where NewsItem is a POCO with a Image and Headline property) Here's the pertinent parts of the MainPage.xaml:
<Page ...
xmlns:data="using:NewsApp.Models" />
....
<GridView Name="FeaturedItems" Grid.Row="0">
<GridView.ItemTemplate>
<DataTemplate x:DataType="data:NewsItem">
<Grid Name="mainPanel" HorizontalAlignment="Stretch" Width="500" >
<Image Source="{x:Bind Image}" HorizontalAlignment="Stretch" />
<TextBlock Text="{x:Bind Headline}" />
</Grid>
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
....
The Image and Headline bind just fine (even though they've not been styled correctly). However, instead I think I need to bind to a User Control to get the styling options I want, control over resizing esp. when using Visual State Triggers and to simplify the XAML in general (at least, this was the technique suggested to me.)
So, I added a new User Control to the project (FeaturedItemControl.xaml), and copied in the DataTemplate's child Grid:
<UserControl ... >
<Grid Name="mainPanel" HorizontalAlignment="Stretch" Width="500" >
<Image Source="{x:Bind Image}" HorizontalAlignment="Stretch" />
<TextBlock Text="{x:Bind Headline}" />
</Grid>
</UserControl>
And then back in the MainPage.xaml, I change the DataTemplate to reference the new FeaturedItemControl:
<GridView Name="FeaturedItems" Grid.Row="0">
<GridView.ItemTemplate>
<DataTemplate x:DataType="data:NewsItem">
<local:FeaturedItemControl HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
</DataTemplate>
</GridView.ItemTemplate>
</GridView>
However, I get the error message for both Image and Headline properties: Invalid binding path 'Headline': Property 'Headline' can't be found on type 'FeaturedItemControl'.
I've tried a few things but am flailing just throwing code at the problem without understanding what I'm doing. Any help would be greatly appreciated.
Thank you for your kind attention.
Using Depechie's answer, I formulated this little cheat cheat for posterity:
Do note that you MUST use this technique to utilize the VisualStateManager with items inside your data bound controls' (GridView, ListView) data templates.
1) Create a User Control.
2) Cut the content of the DataTemplate in your page and paste it into the User Control replacing the template's Grid.
3) Reference the User Control from inside the Data Template:
4) Modify the contents of the User Control changing x:Bind statements to utilize object.property notation:
<UserControl>
<StackPanel>
<Image Source="{x:Bind NewsItem.LeadPhoto}" />
<TextBlock Text="{x:Bind NewsItem.Headline}" />
<TextBlock Text="{x:Bind NewsItem.Subhead}" />
</StackPanel>
</UserControl>
5) Add this in the User Control's Code Behind:
public Models.NewsItem NewsItem { get { return this.DataContext as Models.NewsItem; } }
public ContactTemplate()
{
this.InitializeComponent();
this.DataContextChanged += (s, e) => Bindings.Update();
}
Well it's possible to use x:Bind in user controls, but you'll need to add some extra code behind.
I encountered the same problem in my project, you can see the result here : https://github.com/AppCreativity/Kliva/tree/master/src/Kliva/Controls
So what you need to do is, create a property in the code behind of your user control that points to the correct DataContext.
If you do that, you can use properties of that DataContext in the xaml of your control: for example:
Do note that in the constructor of your control you do need to add: DataContextChanged += (sender, args) => this.Bindings.Update(); because the datacontext will change depending on the page where your control is used!
Then on the page where you are placing this control, you'll also need to do the same to enable the x:bind to work.
You'll see this in my example on the MainPage.DeviceFamily-Mobile.xaml and MainPage.xaml.cs files.
Hope this helps.
x:Bind isn't really hierarchical like Binding/DataContext is. Additionally when you're not directly inside a DataTemplate (such as inside your user control) the object that x:Bind tries to use is 'this' rather than 'this.DataContext'. My current line of thinking on how to solve this sort of issue is to try not to use UserControls anywhere. Instead preferring DataTemplates contained within a ResourceDictionary. There are some pretty strong caveats to this approach though, you will for example crash the xaml compiler if you use x:Bind inside a data template that was created from the ResourceDictionary item template (add new item). you can find a pretty complete example here https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/XamlBind its important to note in the sample where they show the ResourceDictionary being used that its not actually just a ResourceDictionary.xaml its also a ResourceDictionary.xaml.cs (this is where the generated code from x:Bind ends up)
Another option is to add Headline and Image as properties on your user control and x:Bind them from the template, then inside the user control x:Bind as you are currently doing, but now the x:Bind generated path 'this.Headline' will exist. Unfortunately the order things are actually bound means that the x:Bind's you have inside your user control will have to be OneWay rather than the default OneTime. this is because x:Bind OneTime does the bind inside the InitializeComponent call, and any set of properties/DataContext stuff doesn't get done until after that has already run.
So to sum this up, you have two options, use data templates everywhere, or bind to properties that are directly on the user control.
I have a ListView whose Data Context is an ObservableCollection. I then used XAML to format the items and bind to their properties in the ListView in ListView.ItemTemplate.DataTemplate . Now, I want to add a TextBlock here to display the position of the item in the ListView through Binding in XAML. How to do that?
If I got your question right, you just need to add a TextBlock in each item DataTemplate with the index number inside the ListView, right?
If so, you can easily do that by doing something like this:
<DataTemplate x:Key="ItemTemplate">
<Grid>
<!--All your various UI elements here...-->
<!--Add a TextBlock with the formatting you want-->
<TextBlock Text="{Binding Position}"/>
</Grid>
</DataTemplate>
And in C#, add something like this after you've created your Source ObservableCollection, before assigning it to the Property inside your ViewModel:
for (int i = 0; i < myCollection.Count; i++)
{
myCollection[i].Position = Convert.ToString(i);
}
//And then, the usual
Source = myCollection
NB: I'm assuming you have a Property called Source in your ViewModel with INotifyPropertyChanged implemented. You will also have to modify the class you use inside your ObservableCollection and add the Position property of course :)
I am styling the ListPicker with a DataTemplate. All the examples I have read assume that the ListItems are bound complex objects and so can refer to properties on the objects using the usual Binding Property syntax. e.g.
this.myListPicker.Items.Add(new Profile() { Name = "Joe",
Occupation="Button pusher" });
and in the XAML,
<DataTemplate>
<StackPanel>
<TextBox Text="{Binding Name}" />
<TextBox Text="{Binding Occupation}" />
</StackPanel>
</DataTemplate>
However my ListPickers are bound to a List of simple strings and there does not seem to be a property on the string that actually refers to the string.
How do I get a handle to the string inside the DataTemplate so that I can assign them to a e.g. TextBox in the template?
In the example code you show, you do actually have a "complex" object, a Profile, and the binding you specify should work.
If you really just have strings as the items, then the binding in your ItemTemplate would look like:
<TextBox Text="{Binding }" />
The relevant detail is that all ItemsControls (and ListPicker seems to be one) set the DataContext of the view of each item to the item. The binding syntax, above, means "bind to the source itself", and, unless otherwise specified (like with Source or RelativeSource, etc.), the source of any binding is the DataContext.
MSDN has more details here.
I have a WinRT/C#/XAML app with a view that has a vertical ListView of items. Depending on the amount of items the ListView shows a vertical scrollbar. Here's the XAML definition:
<UserControl.Resources>
<CollectionViewSource
x:Name="myViewSource"
Source="{Binding myViewModel.Items}" />
</UserControl.Resources>
...
<ListView
x:Name="myListView"
ItemsSource="{Binding Source={StaticResource myViewSource}}"
SelectedItem="{Binding SelectedItem, Mode=TwoWay}">
</ListView>
Now everytime I navigate to this view, the selected item of the ListView is chosen by setting the databound SelectedItem property in the view model from code behind (OnNavigatedTo). My problem: the ListView doesn't scroll automatically to this selected item. The scrollbar remains at the top of the ListView and the user has to scroll manually to see the selected item.
I tried to execute myListView.ScrollIntoView(MyViewModel.SelectedItem); after setting the SelectedItem in the code behind (in OnNavigatedTo), but it doesn't work. The scrollbar remains at the top.
I'm aware of this thread on SO: Scroll WinRT ListView to particular group .
This seems to be a similar problem. But when I walk the visual tree of the ListView manually or with the WinRT XAML Toolkit, it doesn't find a ScrollViewer (returns null instead).
Thanks to Filip I noticed that calling ScrollIntoView() in OnNavigatedTo() was too early, because the ListView control is not loaded yet in this place.
The first solution idea was to bind the Loaded event of the ListView:
myListView.Loaded += (s, e) =>
myListView.ScrollIntoView(MyViewModel.SelectedItem);
Unfortunately that causes a nasty visual effect, where current ListView items overlap with the selected item for parts of a second, before everything is rearranged well.
The final solution I found is to call ScrollIntoView() asynchronously via the Dispatcher of the view:
myListView.Loaded += (s, e) => Dispatcher.RunAsync(CoreDispatcherPriority.Normal,
() => myListView.ScrollIntoView(MyViewModel.SelectedItem));
With this solution the layouting works fine.
I had a similar need and resolved it in a slightly different manner. I subscribed to the SelectionChangedEvent from the ListView and performed the scrolling within the handler.
XAML:
<ListView x:Name="myListView" SelectionChanged="myListView_SelectionChanged" ...>
</ListView>
Code:
private void myListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
myListView.ScrollIntoView(myListView.SelectedItem);
}
I Have a ListBox and I am defining its ItemsTemplate using a custom control. I want the control to be displayed in different ways depending on the state of cetain properties of the object. How can I access the item that the ListBox.ItemTemplate is bound to?
<ListBox>
<ListBox.ItemTemplate>
<DataTemplate>
<custom:MyControl />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
With in the code of the custom control how would I do something like:
if((this.DataContext as SomeObject).CollectionProperty.Count() > 0)
DoAction();
I was accessing dataContext in the constructor and it was null. I accessed it in the this.Loaded event and it worked fine.