c# - ListView 未更新项目源 ObservableCollection 项目属性更改

Question

考虑以下示例代码:

View .xml

<Grid>
    <ListView Name="NameList" HorizontalAlignment="Left" Height="142" Margin="55,45,0,0" VerticalAlignment="Top" Width="389">
        <ListView.ItemTemplate>
            <DataTemplate>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition Width="Auto"/>
                    </Grid.ColumnDefinitions>
                    <Label Content="{Binding FirstName}"/>
                    <Label Content="{Binding LastName}" Grid.Column="1"/>
                </Grid>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
    <Button Content="Button" HorizontalAlignment="Left" Margin="120,256,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>

</Grid>

View.xml.cs

public partial class MainWindow : Window
{
    ViewModel vm;
    public MainWindow()
    {
        InitializeComponent();
        vm = new ViewModel();
        this.DataContext = vm;
        NameList.ItemsSource = vm.fn;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        vm.fn.Add(new fullname("P", "Q"));
        vm.fn[0].FirstName = "NewName";
    }

}

ViewModel.cs

class ViewModel : INotifyPropertyChanged
{

    public ViewModel()
    {
        fn = new ObservableCollection<fullname>();
        fn.CollectionChanged += ContentCollectionChanged;
        fn.Add(new fullname("A", "B"));
        fn.Add(new fullname("C", "D"));
    }

    public void ContentCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == NotifyCollectionChangedAction.Remove)
        {
            foreach (fullname item in e.OldItems)
            {
                //Removed items
                item.PropertyChanged -= EntityViewModelPropertyChanged;
            }
        }
        else if (e.Action == NotifyCollectionChangedAction.Add)
        {
            foreach (fullname item in e.NewItems)
            {
                //Added items
                item.PropertyChanged += EntityViewModelPropertyChanged;
            }
        }
    }

    public void EntityViewModelPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        //This will get called when the property of an object inside the collection changes
    }

    public ObservableCollection<fullname> _fn;
    public ObservableCollection<fullname> fn
    {
        get { return _fn; }
        set { _fn = value; OnPropertyChanged("fn"); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {

        }
    }
}

模型.cs

class fullname : INotifyPropertyChanged
{
    public fullname(string f, string l)
    {
        FirstName = f;
        LastName = l;
    }

    public string _FirstName;
    public string FirstName
    {
        get { return _FirstName; }
        set { _FirstName = value; OnPropertyChanged("FirstName"); }
    }


    public string _LastName;
    public string LastName
    {
        get { return _LastName; }
        set { _LastName = value; OnPropertyChanged("LastName"); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {

        }
    }
}

如果我在 ObservableCollection 中添加或删除任何项目，它会正确更新 View 中的 ListView，但问题是如果我修改 ObservableCollection 项目属性，ListView 不会更新。

例如:单击上面指定的按钮
A。添加一个新项目(成功反射(reflect)在ListView中)
b.修改第一项的名字(不反射(reflect)在 ListView 中)

我应该怎么做才能使修改反射(reflect)在 View 中。

如果有人能指出我做错了什么，我将不胜感激。

Answer 1

ObservableCollection 事件不会在项目更改时触发，仅在添加、删除或移动时触发。您必须在项目类中实现 INotifyPropertyChanged 接口(interface)，并在集合中注册每个项目事件。

参见 here

如果你在集合中做了很大的改动，你可以提出一个

NotifyCollectionChangedAction.Reset

重置它们的事件

参见 here