Dave Dave - 2 months ago 14
C# Question

Displaying Images in ListView (or something better!) in WPF MVVM using databinding

I am trying to display some images in a ListView and have not been successful. I am using WPF MVVM and the ListView is a holdover from simply displaying suits and rank data. (See my previous post: MVVM in WPF - How to alert ViewModel of changes in Model... or should I? if you are interested!) That is, I could use something other than ListView (if that is the advice) but I would still like to know how to do it with ListView, assuming it's doable. My property I'm binding to in the ViewModel is:

public ObservableCollection<Image> PlayerCardImages{
get{
ObservableCollection<Image> results = new ObservableCollection<Image>();
foreach (CardModel card in PlayerCards)
{
Image img = new Image();
BitmapImage bi3 = new BitmapImage();
bi3.BeginInit();
// TODO: Pick card based on suit/rank. Just get 1 image working now
bi3.UriSource = new Uri("diamond-1.png", UriKind.Relative);
bi3.EndInit();
img.Stretch = Stretch.Fill;
img.Source = bi3;
results.Add(img);
}
return results;
}
}


In my XAML code I'm using:

<Window.Resources>
<DataTemplate x:Key="ImageCell">
<StackPanel Orientation="Horizontal">
<Image Source="{Binding PlayerCardImages}" Width="200" Height="200" Stretch="Fill" ToolTip="Add tooltip"/>
</StackPanel>
</DataTemplate>
</Window.Resources>

<StackPanel Orientation="Vertical">
<Label Content="Player Cards"/>
<ListView Name="lvwTitles" ItemsSource="{Binding}"
IsSynchronizedWithCurrentItem="True"
SelectionMode="Single" ItemTemplate="{StaticResource ImageCell}" Height="59">
</ListView>
</StackPanel>


This idea was shamelessly stolen from: WPF - bind images horizontally to ListView However, it doesn't even appear to databind as evidenced by my breakpoint in PlayerCardImages not being hit.

I also tried the following XAML with somewhat better luck:

<StackPanel Orientation="Vertical">
<Label Content="Player Cards"/>
<ListView

AlternationCount="2"
DataContext="{StaticResource PlayerCardsGroups }"
ItemsSource="{Binding}"
>
<ListView.GroupStyle>
<StaticResourceExtension
ResourceKey="CardGroupStyle"
/>
</ListView.GroupStyle>
<ListView.View>
<GridView>
<GridViewColumn>
<Image Height="50" Width="40"></Image>
</GridViewColumn>
</GridView>
</ListView.View>
</ListView>
</StackPanel>
<Window.Resources>
<CollectionViewSource x:Key="PlayerCardsGroups"
Source="{Binding Path=PlayerCardImages}">
</CollectionViewSource>

<GroupStyle x:Key="CardGroupStyle">
<GroupStyle.HeaderTemplate>
<DataTemplate>
<TextBlock
x:Name="txt"
Background="{StaticResource Brush_HeaderBackground}"
FontWeight="Bold"
Foreground="White"
Margin="1"
Padding="4,2,0,2"
Text="Cards"
/>
</DataTemplate>
</GroupStyle.HeaderTemplate>
</GroupStyle>

<Style x:Key="CardItemStyle" TargetType="{x:Type ListViewItem}">
<!--
Stretch the content of each cell so that we can
right-align text in the Total Sales column.
-->
<Setter Property="HorizontalContentAlignment" Value="Stretch" />
<!--
Bind the IsSelected property of a ListViewItem to the
IsSelected property of a CustomerViewModel object.
-->
<Style.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="ItemsControl.AlternationIndex" Value="1" />
<Condition Property="IsSelected" Value="False" />
<Condition Property="IsMouseOver" Value="False" />
</MultiTrigger.Conditions>
<Setter Property="Background" Value="#EEEEEEEE" />
</MultiTrigger>
</Style.Triggers>
</Style>

</Window.Resources>


this code definitely goes through databinding - my breakpoint is hit at the beginning of the program and whenever items are added to the collection. But no images is displayed. Rather than torture you with more XAML that does not work, perhaps I could ask someone to point me to some code/examples/docs that show how to bind a list of Images to a ListView (or another control if you really feel that ListView is inappropriate). Notice that my collection is the stuff I'm binding to. I notice that with many examples, they are binding to a subproperty. I.e. they may have a collection of albums and for each album they bind to it's property image (see: Showing items as images in a WPF ListView).

Any ideas or help would be much appreciated.

-Dave

Additional info.

Based on suggestions by Clemens, I now have this code for PlayerCardImages:

public ObservableCollection<ImageSource> PlayerCardImages
{
get
{
var results = new ObservableCollection<ImageSource>();

//if (PlayerCards.Count == 0)
// return results;
//else
//{
// results.Add(new BitmapImage(new Uri(@"Images\\" + "diamond-1.png", UriKind.Relative)));
//}
foreach (var card in PlayerCards)
{
results.Add(new BitmapImage(new Uri(@"Images\\" + GetCardFileName(card), UriKind.Relative)));

}
return results;

}


I used the exact XAML he suggested. It almost works. I say "almost" because I noticed strange behavior whereby sometimes 1 card would show and sometimes not (I never got 2 cards). All the getting cards from files and binding seems to be working and I tracked down what I think is key to the last remaining bug (and it's BIZARRE). If in the debugger, I examine results, and further open up results[0] in the debugger, I get that card displayed! I actually have to open up [0] (you see info about height, width, etc.) for this to work. Furthermore if I open up [1], I get that card displayed instead. Why would opening up the debugger info have any effect? For those of you who might ask, what happens if you open up both cards in the debugger... that doesn't work. I get a operation timed out exception. I will say that perhaps my image files are big. 10Kbytes to 30 Kbytes. Is that the problem? I'm guessing not, and that it's a subtle problem with reading in the images or binding. What is going on? Thanks, Dave

Answer

First, you should not use Image controls in your ViewModel. You already have an Image control in the DateTemplate of your view. You want to bind the Source property of this Image conntrol, and the source property of this binding can't be another Image.

Instead your ViewModel would either use ImageSource (or a derived class like BitmapImage) as image type, like this:

public ObservableCollection<ImageSource> PlayerCardImages
{
    get
    {
        var results = new ObservableCollection<ImageSource>();
        foreach (var card in PlayerCards)
        {
            results.Add(new BitmapImage(new Uri(card.ImageUrl)));
        }
        return results;
    }
}

Or simply the image URIs or paths, as there is an automatic conversion from string to ImageSource built into WPF:

public ObservableCollection<string> PlayerCardImages
{
    get
    {
        var results = new ObservableCollection<string>();
        foreach (var card in PlayerCards)
        {
            results.Add(card.ImageUrl);
        }
        return results;
    }
}

You would now bind your Listbox's ItemsSource property to the PlayerCardGames collection, and in the DataTemplate you bind directly to the collection item. The ListView's DataContext has to be set to an instance of the object that defines the PlayerCardGames property.

<ListView ItemsSource="{Binding PlayerCardGames}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <Image Source="{Binding}" />
            </StackPanel>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

UPDATE: As there seems to be a problem with loading the image files, you may try the following method. It loads images synchronously and you are able to step through with the debugger.

public static ImageSource LoadImage(string fileName)
{
    var image = new BitmapImage();

    using (var stream = new FileStream(fileName, FileMode.Open))
    {
        image.BeginInit();
        image.CacheOption = BitmapCacheOption.OnLoad;
        image.StreamSource = stream;
        image.EndInit();
    }

    return image;
}

You can use this method in your PlayerCardGames property getter like this:

foreach (var card in PlayerCards)
{
    results.Add(LoadImage(@"Images\\" + GetCardFileName(card)));
}