我正在尝试开发一个WPF应用程序，该应用程序显示3个视图，我们可以使用侧面菜单进行切换。
第一个视图显示文章。我已经在另一个项目中尝试过这种视图，并且效果很好。
问题是，当我在导航中使用它（具有完全相同的代码）时，除非先单击另一个视图然后单击返回，否则图像或标题将不会显示。
public class Article : INotifyPropertyChanged
{
int id;
string title;
string link;
BitmapImage image;
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public Article(int id, string title, string link, BitmapImage image)
{
Id = id;
Title = title;
Link = link;
Image = image;
}
public int Id
{
get => id;
set { if (value != id) { id = value; NotifyPropertyChanged(); } }
}
public string Title
{
get => title;
set { if (value != title) { title = value; NotifyPropertyChanged(); } }
}
public string Link
{
get => link;
set { if (value != link) { link = value; NotifyPropertyChanged(); } }
}
public BitmapImage Image
{
get => image;
set { if (value != image) { image = value; NotifyPropertyChanged(); } }
}
}
public class ArticlesViewModel : INotifyPropertyChanged
{
Article[] articles;
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
public AccueilViewModel()
{
loadArticle();
}
public Article[] Articles
{
get => articles;
set { if (value != articles) { articles = value; NotifyPropertyChanged(); } }
}
private async void loadArticle()
{
var client = new WordPressClient(App.WordpressLink);
try
{
var asychArticles = GetArticles(client);
await asychArticles;
var articles = asychArticles.Result;
int i = 0;
int a;
foreach (WordPressPCL.Models.Post p in articles)
{
a = p.FeaturedMedia.Value;
var media = GetMedia(client, a);
await media;
BitmapImage bimage = App.getImage(media.Result.SourceUrl);
articleImg[i].Source = bimage;
articleTitle[i].Content = p.Title.Rendered.ToUpper();
articleLink[i] = p.Link;
i++;
if (i == 4) break;
}
}
catch (System.Net.Http.HttpRequestException e)
{
}
}
static async Task<IEnumerable<WordPressPCL.Models.Post>> GetArticles(WordPressClient client)
{
var posts = await client.Posts.GetAll();
return posts;
}
static async Task<WordPressPCL.Models.MediaItem> GetMedia(WordPressClient client, int number)
{
var media = await client.Media.GetByID(number);
return media;
}
}
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="10*"/>
<RowDefinition Height="5*"/>
</Grid.RowDefinitions>
<Grid Name="Article1" Grid.Row="0" Margin="10,10,10,10" DataContext="{Binding Articles[0]}">
<Grid.RowDefinitions>
<RowDefinition Height="5*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Image Name="Image1" Grid.Row="0" Stretch="UniformToFill" Source="{Binding Image}"/>
<Button Name="Titre1" Grid.Row="1" Content="{Binding Title}"/>
</Grid>
<Grid Grid.Row="1">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid Name="Article2" Grid.Column="0" Margin="10,10,10,10" DataContext="{Binding Articles[1]}">
<Grid.RowDefinitions>
<RowDefinition Height="5*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Image Name="Image2" Grid.Row="0" Stretch="UniformToFill" Source="{Binding Image}"/>
<Button Name="Titre2" Grid.Row="1" Content="{Binding Title}"/>
</Grid>
<Grid Name="Article3" Grid.Column="1" Margin="10,10,10,10" DataContext="{Binding Articles[2]}">
<Grid.RowDefinitions>
<RowDefinition Height="5*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Image Name="Image3" Grid.Row="0" Stretch="UniformToFill" Source="{Binding Image}"/>
<Button Name="Titre3" Grid.Row="1" Content="{Binding Title}"/>
</Grid>
<Grid Name="Article4" Grid.Column="2" Margin="10,10,10,10" DataContext="{Binding Articles[3]}">
<Grid.RowDefinitions>
<RowDefinition Height="5*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<Image Name="Image4" Grid.Row="0" Stretch="UniformToFill" Source="{Binding Image}"/>
<Button Name="Titre4" Grid.Row="1" Content="{Binding Title}"/>
</Grid>
</Grid>
</Grid>
<Window.Resources>
<DataTemplate x:Name="ArticlesViewTemplate" DataType="{x:Type viewmodels:ArticlesViewModel}">
<views:ArticlesView DataContext="{Binding}"/>
</DataTemplate>
<DataTemplate x:Name="Feature2ViewTemplate" DataType="{x:Type viewmodels:Feature2ViewModel}">
<views:Feature2View DataContext="{Binding}"/>
</DataTemplate>
<DataTemplate x:Name="Feature3ViewTemplate" DataType="{x:Type viewmodels:Feature3ViewModel}">
<views:Feature3View DataContext="{Binding}"/>
</DataTemplate>
</Window.Resources>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="1*" />
<ColumnDefinition Width="4*" />
</Grid.ColumnDefinitions>
<Grid Grid.Column="0">
<StackPanel Grid.Row="1" VerticalAlignment="Top" Margin="20,20,20,0">
<Button Content="Articles" Click="F1Button_Click"/>
<Button Content="F2" Click="F2Button_Click"/>
<Button Content="F3" Click="F3Button_Click"/>
</StackPanel>
</Grid>
<ContentControl Grid.Column="1" Content="{Binding}"/>
</Grid>
public partial class MainWindow : Window
{
ArticlesViewModel avm;
Feature2ViewModel f2vm;
Feature3ViewModel f3vm;
public MainWindow()
{
InitializeComponent();
}
private void F1Button_Click(object sender, RoutedEventArgs e)
{
if (avm == null) avm = new AccueilViewModel();
DataContext = avm;
}
private void F2Button_Click(object sender, RoutedEventArgs e)
{
if (f2vm == null) f2vm = new CatalogueViewModel();
DataContext = f2vm;
}
private void F3Button_Click(object sender, RoutedEventArgs e)
{
if (f3vm == null) f3vm = new MesFormationsViewModel();
DataContext = f3vm;
}
}
关于问题可能来自何方的任何想法？ 谢谢。
答案 0 :(得分：0)
所以问题似乎出在我使用数组的事实上。最初，DataContext为空，因此即使将图像和标题加载到模型视图中，它们也不会显示在视图中。
通过使用ObservableCollection而不是数组解决了此问题。如果我理解正确，当数组最初为null时，NotifyPropertyChanged（）显然会通知视图。（？）