数据到指定的ItemsSource新的数据之后，从的ListView消失 [英] Data disappears from ListView after assigning new data to ItemsSource

问题描述

我有如下的的ListView ：

<ListView 
    Grid.Row="1" 
    ItemsSource="{Binding MeditationDiary}" >
    <ListView.ItemTemplate>
        <DataTemplate>
            <Grid Width="{Binding ElementName=ListViewHeaders, Path=ActualWidth}" >
                <Grid.ColumnDefinitions>
                    <ColumnDefinition  />
                    <ColumnDefinition  />
                </Grid.ColumnDefinitions>
                <TextBlock 
                    Grid.Column="0" 
                    Text="{Binding StartTime}" />
                <TextBlock 
                    Grid.Column="1" 
                    Text="{Binding TimeMeditated}" />
            </Grid>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

这势必类型的 MeditationDiary 由 MeditationEntries MeditationDiary 属性code>：

This is bound to a MeditationDiary property of type MeditationDiary consisting of MeditationEntries:

public class MeditationDiary : Collection<MeditationEntry> { }

public class MeditationEntry
{
    public DateTime StartTime { get; set; }
    public TimeSpan TimeMeditated { get; set; }
}

的的ListView 绑定到这个 MeditationDiary ：

private MeditationDiary _meditationDiary;
public MeditationDiary MeditationDiary
{
    get
    {
        RaisePropertyChanged(nameof(MeditationDiary));
        return _meditationDiary;
    }
    set
    {
        _meditationDiary = value;
        RaisePropertyChanged(nameof(MeditationDiary));
    }
}

奇怪的是，当我分配一个新的 MeditationDiary 对象属性（其中包含的数据与 MeditationEntries ）的的ListView 确实不再显示数据。

Strangely enough when I assign a new MeditationDiary object to the property (which contains data with MeditationEntries) the ListView does no longer display data.

我指定的 UpdateDiary 方法，新的 MeditationDiary 对象是添加条目之后调用：

I'm assigning the new MeditationDiary object in the UpdateDiary method which is called after adding an entry:

private async void UpdateDiary()
{
    var latestDiary = await _repository.GetAsync();
    MeditationDiary = latestDiary;
}

为什么会这样，以及如何可以把它固定？

Why can this be and how can it be fixed?

推荐答案

这是最有可能的是搞乱了的罪魁祸首你的绑定：

This is most likely the culprit that's messing up your binding:

MeditationDiary = latestDiary;

相反，尝试清除出当前的集合，然后添加新值吧：

Instead, try clearing out the current collection and then adding the new values to it:

MeditationDiary.Clear();

foreach (var entry in latestDiary)
    MeditationDiary.Add(entry);

您可能会拥有你添加新的项目后打电话到 RaisePropertyChanged 的集合。

You'll probably have to call RaisePropertyChanged on the collection after you add the new items.

作为一个方面说明，您可以取代 MeditationDiary 与的ObservableCollection＆LT; MeditationEntry＆GT; ，它会自动通知用户界面当您添加/删除里面的物品。

As a side note, you could replace MeditationDiary with an ObservableCollection<MeditationEntry>, which automatically notifies the UI when you add/remove items in it.

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