LonglistSelector binding to Image Collection does not display - xaml

Question

I have a xaml page. xaml page wants to show two TextBlocks and one LonglistSelector.
the two TextBlocks datasource come from an object(SpecifiedArticle);the LonglistSelctor itemsSource comes from Collection(ImageUriCollection).
when the page launch, the images cannot be displayed.
two TextBlocks data show well
LonglistSelctor does not show images; but i am sure ImageUriCollection's data can be get from the xaml because i tested in a image control and it works
<Image Source="{Binding ImageUriCollection[0].ImageSource}" Width="108" Height="108" Stretch="UniformToFill">
</Image>
i think the issue is in the LonglistSelctor itemsSource binding. anyone can help?
all code below(without the httpclient wrapper):
DetailsPage.cs is below:
public partial class DetailsPage : PhoneApplicationPage
{
DetailsPageViewModel viewModel = new DetailsPageViewModel();
public DetailsPage()
{
InitializeComponent();
this.Loaded += new RoutedEventHandler(DetailsPage_Loaded);
}
private void DetailsPage_Loaded(object sender, RoutedEventArgs e)
{
DataContext = viewModel;
//imageList.ItemsSource = viewModel.ImageUriCollection;
//imageList.ScrollTo(imageList.ItemsSource[imageList.ItemsSource.Count - 1]);
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
string ArticleId = "";
try
{
if (NavigationContext.QueryString.TryGetValue("ArticleId", out ArticleId))
{
Debug.WriteLine(ArticleId);
viewModel.LoadPage(Int32.Parse(ArticleId));
//Debug.WriteLine(viewModel.SpecifiedArticle.Words.ToString());
//LayoutRoot.DataContext = new CollectionViewSource { Source = viewModel.SpecifiedArticle };
}
else
{
MessageBox.Show("No ArticleId passed in.");
}
}
catch(Exception ex)
{
MessageBox.Show("Error in DetailsPage.OnNavigatedTo");
}
}
}
ViewModel is below:
public class DetailsPageViewModel : INotifyPropertyChanged
{
private bool _isLoading = false;
public bool IsLoading
{
get
{
return _isLoading;
}
set
{
_isLoading = value;
NotifyPropertyChanged("IsLoading");
}
}
public DetailsPageViewModel()
{
this.SpecifiedArticle = new Article();
this.ImageUriCollection = new ObservableCollection<Photo>();
this.IsLoading = false;
}
private Article specifiedArticle;
public Article SpecifiedArticle
{
get
{
return specifiedArticle;
}
set
{
specifiedArticle = value;
NotifyPropertyChanged("SpecifiedArticle");
}
}
public ObservableCollection<Photo> ImageUriCollection
{
get;
private set;
}
public void LoadPage(int articleId)
{
IsLoading = true;
ReadArticle(articleId);
}
private async void ReadArticle(int articleId)
{
try
{
Article articleDetails = new Article();
articleDetails = await CollectionHttpClient.GetAsyncByArticleId(articleId);
SpecifiedArticle = articleDetails;
//articleDetails.FirstImage = new Uri(articleDetails.ImagePathList[0]);
if (articleDetails.ImagePathList != null)
{
foreach (var item in articleDetails.ImagePathList)
{
Photo p = new Photo();
p.ImageSource = new Uri(item);
this.ImageUriCollection.Add(p);
}
//var image = await CollectionHttpClient.GetImageByImageName(articleDetails.ImagePath);
//Bytelist.Add(image);
}
else
{
this.ImageUriCollection = null;
}
IsLoading = false;
}
catch(Exception ex)
{
MessageBox.Show("sorry, no data.");
IsLoading = false;
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
xaml is:
<phone:PhoneApplicationPage.Resources>
<vm:DetailsPageViewModel x:Key="viewModel"/>
<phone:JumpListItemBackgroundConverter x:Key="BackgroundConverter"/>
<phone:JumpListItemForegroundConverter x:Key="ForegroundConverter"/>
<Style x:Key="JumpListStyle" TargetType="phone:LongListSelector">
<Setter Property="LayoutMode" Value="List" />
<Setter Property="Margin" Value="12,12,0,0"/>
<Setter Property="ItemTemplate">
<Setter.Value>
<DataTemplate>
<Border Background="{Binding Converter={StaticResource BackgroundConverter}}"
Width="470"
Height="70"
Margin="6">
<TextBlock Text="{Binding Key}"
Foreground="{Binding Converter={StaticResource ForegroundConverter}}"
FontFamily="{StaticResource PhoneFontFamilySemiBold}"
FontSize="28"
Padding="2"
VerticalAlignment="Bottom"/>
</Border>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
<DataTemplate x:Key="GroupHeader">
<Border Background="Transparent">
<Border Background="Transparent" BorderBrush="Transparent" BorderThickness="1"
Width="400" Height="90"
HorizontalAlignment="Left">
<TextBlock Text="Pictures:"
Foreground="{StaticResource PhoneAccentBrush}"
FontSize="28"
Padding="2"
FontFamily="{StaticResource PhoneFontFamilySemiLight}"
HorizontalAlignment="Left"
VerticalAlignment="Center"/>
</Border>
</Border>
</DataTemplate>
<DataTemplate x:Key="ItemTemplate">
<StackPanel Height="108" Width="108" Margin="6,6">
<Image Width="108" Height="108" Stretch="UniformToFill">
<Image.Source>
<BitmapImage UriSource="{Binding ImageSource}" CreateOptions="BackgroundCreation"/>
</Image.Source>
</Image>
</StackPanel>
</DataTemplate>
</phone:PhoneApplicationPage.Resources>
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<!--TitlePanel contains the name of the application and page title-->
<StackPanel Grid.Row="0" Margin="12,17,0,28">
<TextBlock Text="{Binding Path=SpecifiedArticle.Subject }" TextWrapping="Wrap" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel>
<!--ContentPanel - place images here-->
<Grid x:Name="ContentPanel" Grid.Row="1" Background="Transparent">
<!--
<Image Source="{Binding ImageUriCollection[0].ImageSource}" Width="108" Height="108" Stretch="UniformToFill">
<Image.Source>
<BitmapImage UriSource="{Binding ImageSource}" CreateOptions="BackgroundCreation"/>
</Image.Source>
</Image>
-->
<phone:LongListSelector Name="imageList" Margin="13,-30,0,0"
ItemsSource="{Binding ImageUriCollection}"
ItemTemplate="{StaticResource ItemTemplate}"
JumpListStyle="{StaticResource JumpListStyle}"
IsGroupingEnabled="True"
LayoutMode="Grid"
GridCellSize="108,108"/>
</Grid>
<!--ContentPanel - place article words here-->
<StackPanel Grid.Row="2" Margin="12,17,0,28">
<TextBlock Text="{Binding Path=SpecifiedArticle.Words}" TextWrapping="Wrap" Style="{StaticResource PhoneTextNormalStyle}"/>
</StackPanel>
</Grid>
DetailsPage.cs is below:
public partial class DetailsPage : PhoneApplicationPage
{
DetailsPageViewModel viewModel = new DetailsPageViewModel();
public DetailsPage()
{
InitializeComponent();
this.Loaded += new RoutedEventHandler(DetailsPage_Loaded);
}
private void DetailsPage_Loaded(object sender, RoutedEventArgs e)
{
DataContext = viewModel;
//imageList.ItemsSource = viewModel.ImageUriCollection;
//imageList.ScrollTo(imageList.ItemsSource[imageList.ItemsSource.Count - 1]);
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
string ArticleId = "";
try
{
if (NavigationContext.QueryString.TryGetValue("ArticleId", out ArticleId))
{
Debug.WriteLine(ArticleId);
viewModel.LoadPage(Int32.Parse(ArticleId));
//Debug.WriteLine(viewModel.SpecifiedArticle.Words.ToString());
//LayoutRoot.DataContext = new CollectionViewSource { Source = viewModel.SpecifiedArticle };
}
else
{
MessageBox.Show("No ArticleId passed in.");
}
}
catch(Exception ex)
{
MessageBox.Show("Error in DetailsPage.OnNavigatedTo");
}
}
}
ViewModel is below:
public class DetailsPageViewModel : INotifyPropertyChanged
{
private bool _isLoading = false;
public bool IsLoading
{
get
{
return _isLoading;
}
set
{
_isLoading = value;
NotifyPropertyChanged("IsLoading");
}
}
public DetailsPageViewModel()
{
this.SpecifiedArticle = new Article();
this.ImageUriCollection = new ObservableCollection<Photo>();
this.IsLoading = false;
}
private Article specifiedArticle;
public Article SpecifiedArticle
{
get
{
return specifiedArticle;
}
set
{
specifiedArticle = value;
NotifyPropertyChanged("SpecifiedArticle");
}
}
public ObservableCollection<Photo> ImageUriCollection
{
get;
private set;
}
public void LoadPage(int articleId)
{
IsLoading = true;
ReadArticle(articleId);
}
private async void ReadArticle(int articleId)
{
try
{
Article articleDetails = new Article();
articleDetails = await CollectionHttpClient.GetAsyncByArticleId(articleId);
SpecifiedArticle = articleDetails;
//articleDetails.FirstImage = new Uri(articleDetails.ImagePathList[0]);
if (articleDetails.ImagePathList != null)
{
foreach (var item in articleDetails.ImagePathList)
{
Photo p = new Photo();
p.ImageSource = new Uri(item);
this.ImageUriCollection.Add(p);
}
//var image = await CollectionHttpClient.GetImageByImageName(articleDetails.ImagePath);
//Bytelist.Add(image);
}
else
{
this.ImageUriCollection = null;
}
IsLoading = false;
}
catch(Exception ex)
{
MessageBox.Show("sorry, no data.");
IsLoading = false;
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (null != handler)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}

Answer 1

Try this-
just change your ItemTemplate DataTemplate to a simpler one
If it works, add one change at a time.
<DataTemplate x:Key="ItemTemplate">
<Image Source="{Binding ImageSource}" Stretch="UniformToFill"/>
</DataTemplate>

Answer 2

it is the style problem.
delete the style, try again, images show well
<phone:LongListSelector Name="imageList" Margin="13,-30,0,0"
ItemsSource="{Binding ImageUriCollection}"
ItemTemplate="{StaticResource ItemTemplate}"
LayoutMode="Grid"
GridCellSize="108,108">
</phone:LongListSelector>
in the JumpListStyle, it contains the textblock which is not belong to the xaml, that is why the LonglistSelector does not display anything after binding collectly.