I am binding a Xaml Combobox. Can i use Stackpanel or List? Can u explain how to bind data in such a way?
To start you'll need some data with public properties for the URI of the image and text you want to display with it. Here's a simple example to use below:
public class ImageOption
{
public string ImageUri { get; set; }
public string ImageText { get; set; }
}
You'll then need another public property to hold some collection of that data item. This property needs to be on an object that can be set as a DataContext somewhere in your view or can be assigned directly to your ComboBox in code-behind:
public ObservableCollection<ImageOption> ImageList { get; private set; }
Assuming that the DataContext of some parent element of the ComboBox has been assigned to the object containing the ImageList property you can then use this to bind the collection and display a simple image and text for each item:
<ComboBox ItemsSource="{Binding ImageList}">
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<Image Source="{Binding Path=ImageUri}" />
<TextBlock Text="{Binding Path=ImageText}"/>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
You will probably also want some size constraints on your Image by setting MaxWidth and/or MaxHeight.
Related
In an AvaloniaUI window, I want to have a TabControl whose tabs are added and removed from an ObservableCollection<T>. The tab's "title" (the text appearing on the tab strip) should be set inside each item of the collection, which could belong to a different type.
For that I defined a type:
public abstract class TabViewModelBase : ViewModelBase
{
public abstract string TabHeader { get; }
}
and my collection is defined like this:
public ObservableCollection<TabViewModelBase> OpenTabs { get; } = new();
In the axaml file, this is the definition of the TabControl:
<TabControl Items="{Binding OpenTabs}">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding TabHeader}"/>
</DataTemplate>
</TabControl.ItemTemplate>
</TabControl>
So far, this works like a charm.
The problem begins when I also want to set up a container for the view inside each tab, which should not be a part of the contained view itself. I've tried by editing the xaml above and setting a ContentTemplate like this:
<TabControl Items="{Binding OpenTabs}">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding TabHeader}"/>
</DataTemplate>
</TabControl.ItemTemplate>
<TabControl.ContentTemplate>
<DataTemplate>
<Border Child="{Binding}"/>
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
However this results in the following error:
[Binding] Error in binding to 'Avalonia.Controls.Border'.'Child': 'Could not convert 'Project.ViewModels.TestingViewModel' to 'IControl'.'
This seems to be because ViewLocator, which automatically matches a view model to a view based on its name, is not being called. I assume this is because I've defined a DataTemplate inside TabControl.ContentTemplate.
Is it possible to instruct Avalonia to use ViewLocator inside TabControl.ContentTemplate, so that a view is selected based on its name?
<Border Child="{Binding}"/>
Border expects an actual control as a child, not a view model. You need to use ContentControl instead. It can also have it's own data template or view locator.
I found a way to work around the issue, by defining an IValueConverter that uses ViewLocator internally:
public class ViewModelValueConverter : IValueConverter
{
public object? Convert(
object value, Type targetType, object parameter, CultureInfo culture
)
{
if (value == null)
return null;
if (
value is ViewModelBase viewModel
&& targetType.IsAssignableFrom(typeof(IControl))
)
{
ViewLocator viewLocator = new();
return viewLocator.Build(value);
}
throw new NotSupportedException();
}
public object ConvertBack(
object value, Type targetType, object parameter, CultureInfo culture
)
{
throw new NotSupportedException();
}
}
and using it in XAML:
<Window.Resources>
<local:ViewModelValueConverter x:Key="variableView"/>
</Window.Resources>
<TabControl Items="{Binding OpenTabs}">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding TabHeader}"/>
</DataTemplate>
</TabControl.ItemTemplate>
<TabControl.ContentTemplate>
<DataTemplate>
<Border Child="{Binding, Converter={StaticResource variableView}}"/>
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
but it feels like there might be a simpler solution.
I have 2 DataTemplates for displaying the contents of ClassA or ClassB inside a single ListView; which template to select will be based on a RadioButton selection by the user.
Is it possible to change the ItemTemplate of a ListView (in XAML) based on user input dynamically at runtime?
An example snippet of code:
XAML Page:
<Page...>
<Page.Resources>
<DataTemplate x:Key="ClassAListViewItemTemplate" x:DataType="vm:ClassA" ... />
<DataTemplate x:Key="ClassBListViewItemTemplate" x:DataType="vm:ClassB" ... />
</Page.Resources>
<RelativePanel>
<RadioButton Content="ClassA" ... />
<RadioButton Content="ClassB" ... />
<ListView DataContext="{Binding Path=MainViewModel}"
ItemsSource="{Binding ListOfClassAOrB, Mode=TwoWay}"
ItemTemplate="{StaticResource ClassAListViewItemTemplate}"/>
</RelativePanel>
</Page>
I have stripped the code down somewhat to the essentials, but I would like to be able to change the following at runtime:
ItemTemplate="{StaticResource ClassAListViewItemTemplate}"
I have seen solutions for Classic WPF applications that use Style.Triggers, but these aren't applicable for UWP
Marco Minerva's blog on Adaptive Triggers, RelativePanel and DataTemplate in the Universal Windows Platform talks of using UserControls within DataTemplates to modify the visual state using Adaptive Triggers, but this doesn't take into account switching out of templates based on user input
The closest answer I have found to my problem is another blog he wrote "Dynamically choose DataTemplate in WinRT" where there is an element of code-behind involved - but it only appears to be an if statement - but its the cleanest solution I have come across thus far, and what I'd like to replicate in XAML
Thanks
you need to use overwrite SelectTemplateCore of Data template. Change your view model like this.
Below code will helps you.
public class SampleViewModel : DataTemplateSelector
{
public DataTemplate ClassAListViewItemTemplate{ get; set; }
public DataTemplate ClassBListViewItemTemplate{ get; set; }
protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
{
var itemsData = item as SampleClass; // add your Data class
if (itemsData.IsAddButton == false) // define any property to select the datatemplate
{
return ClassAListViewItemTemplate;
}
else
{
return ClassBListViewItemTemplate;
}
}
}
Add your two datatemplates to one key, and give the key to ItemTemplateSelector property in gridview.
<viewModels:SampleViewModel x:Key="FeedbackTempateSelector"
ClassAListViewItemTemplate="{StaticResource ClassAListViewItemTemplate}"
ClassBListViewItemTemplate="{StaticResource ClassBListViewItemTemplate}">
</viewModels:SampleViewModel>
I want to bind the Source of an Image (in WinRT XAML) to the ImageSource property of a view model called ServiceEnvoy, which points to an image in my project's /Assets directory. Here is the view model:
public class ServiceEnvoy
{
public ServiceEnvoy(string name, ImageSource source)
{
this.Name = name;
this.ImageSource = source;
}
public string Name { get; private set; }
public ImageSource ImageSource { get; private set; }
}
Here is the XAML of the ListView I want to expose the view model:
<ListView ItemsSource="{Binding Services}"
...>
<ListView.ItemTemplate>
<DataTemplate>
<Button>
<Button.Content>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}"/> <!--Works fine-->
<Image Source="{Binding ImageSource}"/> <!--Does not-->
</StackPanel>
</Button.Content>
</Button>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
There's another complication, however: the view model is deserialized from JSON to be loaded onto the main page.
Here is the JSON I have so far:
{
"Services": [
{
"Name": "OneDrive",
"Image": "onedrive.png"
}
]
}
A ServiceEnvoyExtractor class (found here on Pastebin) extracts the view model by appending "ms-appx:///Assets/" to "Image" and creating a Uri/BitmapImage out of that. I'm not sure if that was the problem, but I tried changing the JSON to "Image": "/Assets/onedrive.png" or "ms-appx:///Assets/onedrive.png" and rebuilding, but the designer still did not display the image. However, it works fine when I run it on my phone.
My d:DataContext is: d:DataContext="{Binding Source={d:DesignData Source=/Data/ServiceRecords.json, Type=data:DesignableServiceEnvoyCollection}}"
Well, that was rather simple.
After a few hours of frustrating myself with the type of the ImageSource and renaming it and testing other controls with it and fiddling around with the JSON, I realized that while its key was "Image", I was binding to "ImageSource".
That, and changing its directory to "Assets/onedrive.png" fixed the problem.
EDIT: The XAML also seemed to throw an error about how ImageSource properties could not be serialized; changing the property to type string fixed the problem.
I have a Windows 8.1 application. I have a requirement of selecting different templates based on a certain value. For this purpose I'm using ContentPresenter in the xaml with a Static Resource TemplateSelector.
Here's my datatemplates and templateselector in xaml resources
<DataTemplate x:Key="template1">
<TextBox Text="Temp 1" />
</DataTemplate>
<DataTemplate x:Key="template2">
<TextBox Text="Temp 2" />
</DataTemplate>
<DataTemplate x:Key="template3">
<TextBox Text="Temp 3" />
</DataTemplate>
<template:BalanceTypesTemplateSelector x:Key="MySelector"
Template1="{StaticResource template1}"
Template2="{StaticResource template2}"
Template3="{StaticResource template3}" />
Here's my ContentPresenter XAML
<ContentPresenter ContentTemplateSelector="{StaticResource MySelector}"
Content="{Binding MyData}" />
Here's my Template Selector Code
public class BalanceTypesTemplateSelector : DataTemplateSelector
{
public DataTemplate Template1 { get; set; }
public DataTemplate Template2 { get; set; }
public DataTemplate Template3 { get; set; }
protected override DataTemplate SelectTemplateCore(object item)
{
var type = item.ToString();
switch (type)
{
case "t1":
return Template1;
case "t2":
return Template1;
case "t3":
return Template3;
default:
throw new NotSupportedException();
}
}
return null;
}
}
But it's not hitting the templateselector code at all. The string that is bound is directly displayed on the display when I run the app.
I would be glad if some one point me in the right direction. Thanks in Advance.
Basically, you're only overriding one of the SelectTemplateCore overloads.
From the DataTemplateSelector docs:
To define an effective DataTemplateSelector subclass, provide implementations for SelectTemplateCore(Object) and SelectTemplateCore(Object, DependencyObject)
Once you provide an implementation for SelectTemplateCore(Object, DependencyObject), it will get invoked.
I tried to do it, but there was another problem I encountered - the object is always null (and not the Content/DataContext of the ContentPresenter).
I asked Google why is that and found this discussion. From it:
The ContentControl and ContentPresenter appear to be broken in Windows RT when used with a ContentTemplateSelector property bound to a view model. The 'object' parameter to the template selector is always null.
There's also a workaround for this problem at the end of that discussion.
Hope this helps. :)
Using ContentControl instead of ContentPresenter is working for me. Thanks #KaiBrummund for his comment on my question.
Hard to put into words for title. I have a normal WPF combo box and the data (list of names) is getting pulled from SQL and I want to change the text colour and
Foreground ="Black"
only seems to be working when I actually select the user. Any suggestions how else I can change this?
EDIT: I haven't tried any other things as of yet as I know that way to actually change the text colour.
EDIT2:
<ComboBox x:Name="cmbDepartment" HorizontalAlignment="Left" Height="25" Margin="92,580,0,0" VerticalAlignment="Top" Width="400" Foreground="#FFA2A2A2" FontSize="13"/>
This is my XAML code for the combo box. I have figured out that my theme is making it blue but when I change the font colour on my theme everything then turns that colour in my application. Is there a piece of code that I can write in my XAML which will set the colour of everything in the combo box grey, without changing the colours in my application.
I assume that initially the ComboBox shows no selected value and once you click on it it shows the list of names with the proper color (being whatever color you assigned through the Foreground property).
If so, may it be the case that you haven't selected an item? Once you have set the items, you must select an item (e.g. SelectedIndex, SelectedValue) if you don't want the ComboBox selection to appear empty.
Excuse me if this is not the case, but the question was pretty vague..
Here is a example using MVVM
XAML
<Window x:Class="SelfBinding.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<ComboBox ItemsSource="{Binding MyItems}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name}" Foreground="{Binding Name}"/>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</Grid>
</Window>
codebehind
using System.Collections.Generic;
using System.Windows;
namespace SelfBinding
{
/// <summary>
/// Interaktionslogik für MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new MyViewModel();
}
}
public class MyViewModel
{
public List<MyItem> MyItems { get; set; }
public MyViewModel()
{
MyItems = new List<MyItem>();
MyItems.Add(new MyItem { Name = "Black" });
MyItems.Add(new MyItem { Name = "Red" });
MyItems.Add(new MyItem { Name = "Orange" });
MyItems.Add(new MyItem { Name = "Green" });
}
}
public class MyItem
{
public string Name { get; set; }
}
}
to test it on your on create a new WPFproject an copy & past the code
Maybe you can override the theme colors in the combobox resources. This is an exaple for doing so.
I just don't know what exactly is the key that you need to override. I guess you can google that.
good luck.