wpf 添加项目时，Observablecollection 不更新列表
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Observablecollection not updating list, when an item gets added
提问by HaloMediaz
I'm using the MVVM pattern and want to update a ListView using an observable collection. I went through several SO questions, but cannot see what I'm doing wrong. Any help is much appreciated. Thanks.
我正在使用 MVVM 模式并希望使用可观察集合更新 ListView。我经历了几个 SO 问题，但看不出我做错了什么。任何帮助深表感谢。谢谢。
View.xaml
查看.xaml
Namespace: xmlns:local="clr-namespace:MusicPlayer.ViewModel"
命名空间： xmlns:local="clr-namespace:MusicPlayer.ViewModel"
DataContext
数据上下文
<UserControl.DataContext>
<local:AllTracksViewModel/>
</UserControl.DataContext>
ListView
列表显示
<ListView x:Name="TrackListView"
ItemsSource="{Binding Path=TrackListObservable}">
...
<ListView.View>
<GridView>
<GridViewColumn Header="Title" Width="250" DisplayMemberBinding="{Binding Title}" />
<GridViewColumn Header="Album" Width="200" DisplayMemberBinding="{Binding Album}" />
<GridViewColumn Header="Artist" Width="150" DisplayMemberBinding="{Binding Artist}" />
<GridViewColumn Header="Duration" Width="100" DisplayMemberBinding="{Binding FormattedDuration}" />
</GridView>
</ListView.View>
</ListView>
ViewModel.cs
视图模型.cs
public class AllTracksViewModel
{
public ObservableCollection<Track> TrackListObservable { get; private set; }
public AllTracksViewModel()
{
TrackListObservable = new ObservableCollection<Track>();
}
}
I verified that items are definitely getting added to the observable. Again, thanks for the help.
我确认项目肯定会添加到可观察对象中。再一次感谢你的帮助。
回答by Arnaud Weil
Change your code to this:
将您的代码更改为：
public class AllTracksViewModel : INotifyPropertyChanged
{
ObservableCollection<Track> trackListObservable;
public event PropertyChangedEventHandler PropertyChanged;
public ObservableCollection<Track> TrackListObservable {
get { return trackListObservable; }
set {
trackListObservable = value;
if(PropertyChanged!=null) {
PropertyChanged(this, new PropertyChangedEventArgs("TrackListObservable"));
}
}
}
public AllTracksViewModel()
{
TrackListObservable = new ObservableCollection<Track>();
}
}
Just to explain why: every property of your ViewModel should notify of its changes.
只是为了解释原因：您的 ViewModel 的每个属性都应该通知其更改。
回答by M.kazem Akhgary
You should write this as itemsource
你应该把它写成 itemsource
ItemsSource="{Binding ViewModel.TrackListObservable}"
And also set data context of windows to it self.
并将窗口的数据上下文设置为它自己。
<Window DataContext="{Binding RelativeSource={RelativeSource Self}}" ...
With this property in MainWindow.
在 MainWindow 中使用此属性。
public AllTracksViewModel ViewModel { get; } = new AllTracksViewModel();
Note that you have to add items to this property. ViewModel.TrackListObservable
请注意，您必须向此属性添加项目。 ViewModel.TrackListObservable
You should also remove
你也应该删除
<UserControl.DataContext>
<local:AllTracksViewModel/>
</UserControl.DataContext>
since the data context is the main window it self, thats why itemsource is set to ViewModel.TrackListObservable
由于数据上下文是它自己的主窗口，这就是为什么将 itemsource 设置为 ViewModel.TrackListObservable
回答by StepUp
Your code looks correctly. However, I cannot see the method which populates your TrackListObservable. I suggest to you to call a populating method FillDatainside of a constructor. Let me show an example:
您的代码看起来正确。但是，我看不到填充您的TrackListObservable. 我建议您FillData在构造函数中调用填充方法。让我举个例子：
public class AllTracksViewModel
{
private ObservableCollection<Track> _trackListObservable;
public ObservableCollection<Track> TrackListObservable
{
get { return _trackListObservable; }
set {
_trackListObservable = value;
}
}
public AllTracksViewModel()
{
FillData();
}
private void FillData()
{
_trackListObservable = new ObservableCollection<Track>();
for (int i = 0; i < 30; i++)
{
TrackListObservable.Add(new Track() { Title = "Ben & Joseph " + i.ToString(),
Artist = "Albahari" });
}
}
}
Please, see a work example of binding ListView using MVVM pattern.
请参阅使用 MVVM 模式绑定 ListView的工作示例。
回答by Vinod Kumar
Here your Property TrackListObservablemust be a INotify Property or Dependency Property.So that only you can achieve the result what you want.
在这里，您的属性TrackListObservable必须是 INotify 属性或依赖属性。这样只有您才能达到您想要的结果。
Refer the below link regards INotify Property: https://msdn.microsoft.com/library/ms743695(v=vs.100).aspx
请参阅以下有关 INotify 属性的链接：https://msdn.microsoft.com/library/ms743695(v =vs.100).aspx
