mvvm - 可观察的集合更改后，UI不变

Question

嗨，我有observablecollection，我从服务器获取数据，完成后我想刷新page.Data即将到来，但我在屏幕上看不到它，我找不到错误。我实现了INotifypropertychanged，但我认为它无法正常运行。当我放置断点时，我每次看到的都是PropertyChanged事件为null。

我的课

public class Ulke:INotifyPropertyChanged
{
    private int _ulkeID;
    public int UlkeID 
    { 
        get { return _ulkeID; } 
        set { _ulkeID = value; NotifyPropertyChanged(); } 
    }

    private string _adi;
    public string Adi 
    { 
        get { return _adi; } 
        set { _adi = value; NotifyPropertyChanged(); } 
    }

    public string DiyanetID { get; set; }
    public bool EyaletVarmi { get; set; }

    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

Ulke储存库类

public class UlkeRepository : INotifyPropertyChanged
{
    public UlkeRepository()
    {
        _ulkeler = new ObservableCollection<Ulke>();
        ulkeler.Add(new Ulke { UlkeID = 3, EyaletVarmi = true, DiyanetID = "3", Adi = "Moliba" });
        ulkeler.Add(new Ulke { UlkeID = 5, EyaletVarmi = true, DiyanetID = "3", Adi = "As" });
    }

    private ObservableCollection<Ulke> _ulkeler;
    public ObservableCollection<Ulke> ulkeler 
    { 
            get { return _ulkeler; }
            set { _ulkeler = value; NotifyPropertyChanged(); } 
    }

    public async Task UlkeGetir()
    {
        JsonDownloader js = new JsonDownloader();
        var result = await js.GetDataFromUrl<Ulke>("http://www.example.com/A/UlkeGetir");
        ulkeler = result;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

}

MyPageLoaded代码

   this.DataContext = ulke.ulkeler;
   liste.DataContext = ulke.ulkeler;         
   ulke.UlkeGetir();

Xaml代码

<ListBox x:Name="liste"
         ItemsSource="{Binding Mode=TwoWay}" SelectionChanged="liste_SelectionChanged">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Adi}"/>
                </DataTemplate>
            </ListBox.ItemTemplate>
 </ListBox>

Answer 1

在查看源代码之后更新了解决方案:

一切正常，您只需要注意编译器警告即可。

HubPage.xaml.cs

功能UlkeYukle更新(您忘记等待)

UlkeRepository ulke;
private async void UlkeYukle()
{
    ulke = new UlkeRepository();        
    await ulke.UlkeGetir();         // you forgot this       
}


// this is a function to test your OnPropertyChange
private void Button_Click(object sender, RoutedEventArgs e)
{
    ulke.ulkeler.Insert(0, new Ulke { UlkeID = 5, EyaletVarmi = true, DiyanetID = "3", Adi = "A_TEST" }); // inssert at top
    ulke.ulkeler[0].Adi = "Changing Title Again";
}

出于调试目的，我在模板中添加了一个Button(以便我们可以测试事实之后是否更新)

HubPage.xaml

<HubSection x:Uid="HubSection1" x:Name="hub1" Header="SECTION 1" DataContext="{Binding Mode=TwoWay}" HeaderTemplate="{ThemeResource HubSectionHeaderTemplate}">
    <DataTemplate>
        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="80*"/>
                <RowDefinition Height="20*"/>
            </Grid.RowDefinitions>
            <ListView 
            ItemsSource="{Binding Mode=TwoWay}"
            IsItemClickEnabled="True"
            ItemClick="GroupSection_ItemClick"
            ContinuumNavigationTransitionInfo.ExitElementContainer="True">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Margin="0,0,0,27.5">
                            <TextBlock Text="{Binding Adi}" Style="{ThemeResource ListViewItemTextBlockStyle}" />
                        </StackPanel>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
            <Button Click="Button_Click" Grid.Row="1"></Button>
        </Grid>
    </DataTemplate>
</HubSection>