依存関係プロパティ GroupDescription を使用して、リスト ビュー項目ソースのプロパティに従って WPF リスト ビュー内の項目をグループ化しています。
私の問題は、 GroupDescription 値が変更された場合にのみグループ化が更新され、リストビューソース内のアイテムのバインドされたプロパティが変更されないことです。
以下の例では、GroupDescription が city に設定されているため、グループの説明は "City: Hamburg" になります。ただし、アイテムの都市プロパティが変更されても、リスト ビュー内のグループ化は更新されません。つまり、グループ「都市: ハンブルグ」内に都市「ベルリン」のアイテムが存在することになります。
グループ化は、GroupDescription が更新された後にのみ更新されます。GroupDescription を PersonId に変更し、すぐに City に戻す PersonPropertyChanged メソッドを使用して回避策を見つけようとしました。ただし、この回避策により、スクロール位置がたとえばリストビューの中央または最後にある場合、リストビューが常に先頭に戻ることになります。プロパティが変化する何百ものエントリを含むリスト ビューを操作する場合、これは非常に面倒です。
項目のプロパティが変更された後、リスト ビューをトップに戻さずにグループ化を「更新」する方法はありますか?
助けてくれてありがとう！トーマス
GroupingListView.cs
using System.Windows.Controls;
using System.Windows;
using System.Windows.Data;
namespace WpfApplication
{
/// <summary>
/// Enhanced list view based on WPF ListView with dependency properties for GroupDescriptions
/// </summary>
public class GroupingListView : ListView
{
/// <summary>
/// Dependency property for group descriptions
/// </summary>
public string GroupDescription
{
get { return (string)GetValue(GroupDescriptionProperty); }
set { SetValue(GroupDescriptionProperty, value); }
}
/// <summary>
/// Using a DependencyProperty as the backing store for GroupDescription. This enables animation, styling, binding, etc...
/// </summary>
public static readonly DependencyProperty GroupDescriptionProperty =
DependencyProperty.Register("GroupDescription",
typeof(string),
typeof(GroupingListView),
new UIPropertyMetadata(string.Empty, GroupDescriptionChanged));
private static void GroupDescriptionChanged(DependencyObject source, DependencyPropertyChangedEventArgs args)
{
var control = source as GroupingListView;
// Stop if source is not of type DetailedListView
if (control == null) return;
// Stop if myView is not available, myView can not group, groupdescription missing\
// or the argument is empty
var myView = (CollectionView)CollectionViewSource.GetDefaultView(control.ItemsSource);
if (myView == null || !myView.CanGroup || (string) args.NewValue == string.Empty ||
myView.GroupDescriptions == null)
{
return;
}
myView.GroupDescriptions.Clear();
// If a group description already
if(myView.GroupDescriptions.Count > 0)
{
var prop = myView.GroupDescriptions[0] as PropertyGroupDescription;
if(prop != null)
{
if(!prop.PropertyName.Equals((string)args.NewValue))
{
myView.GroupDescriptions.Clear();
}
}
}
// Stop if at this point a group description still exists. This means the newValue is
// equal to the old value and nothing needs to be changed
if (myView.GroupDescriptions.Count != 0) return;
// If this code is reached newValue is different than the current groupDescription value
// therefore the newValue has to be added as PropertyGroupDescription
var groupDescription = new PropertyGroupDescription((string)args.NewValue);
// Clear and add the description only if it's not already existing
myView.GroupDescriptions.Add(groupDescription);
}
}
}
MainWindow.xaml
<Window x:Class="WpfApplication.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:WpfApplication="clr-namespace:WpfApplication"
Title="MainWindow" Height="300" Width="300">
<StackPanel>
<Button Content="Change" Click="btnChangeCity" Height="22"/><Button Content="Change back" Click="btnChangeCityBack" Height="22"/>
<WpfApplication:GroupingListView ItemsSource="{Binding Persons}" Height="200"
GroupDescription="{Binding GroupDescription}" x:Name="GroupingListView">
<ListView.GroupStyle>
<GroupStyle>
<GroupStyle.HeaderTemplate>
<DataTemplate>
<Grid HorizontalAlignment="Stretch">
<Border HorizontalAlignment="Stretch" BorderBrush="Transparent" BorderThickness="1" CornerRadius="3">
<Border HorizontalAlignment="Stretch" BorderBrush="LightGray" BorderThickness="0,0,0,1" CornerRadius="0">
<StackPanel Orientation="Horizontal">
<TextBlock Foreground="LightGray" Text="{Binding GroupDescription, ElementName=GroupingListView}"/>
<TextBlock Foreground="LightGray" Text=" : "/>
<TextBlock Foreground="LightGray" Text="{Binding Name}" HorizontalAlignment="Stretch"/>
</StackPanel>
</Border>
</Border>
</Grid>
</DataTemplate>
</GroupStyle.HeaderTemplate>
</GroupStyle>
</ListView.GroupStyle>
<ListView.View>
<GridView>
<GridViewColumn Header="PersonId" Width="100">
<GridViewColumn.CellTemplate>
<DataTemplate>
<TextBlock TextTrimming="CharacterEllipsis" Text="{Binding PersonId, Mode=Default}"/>
</DataTemplate>
</GridViewColumn.CellTemplate>
</GridViewColumn>
<GridViewColumn Header="City" Width="100">
<GridViewColumn.CellTemplate>
<DataTemplate>
<TextBlock TextTrimming="CharacterEllipsis" Text="{Binding City, Mode=Default}"/>
</DataTemplate>
</GridViewColumn.CellTemplate>
</GridViewColumn>
</GridView>
</ListView.View>
</WpfApplication:GroupingListView>
</StackPanel>
</Window>
MainWindow.xaml.cs
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
namespace WpfApplication
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : INotifyPropertyChanged
{
public class Person : INotifyPropertyChanged
{
public Person(string personId, string city)
{
PersonId = personId;
City = city;
}
private string _personId;
private string _city;
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler pc = PropertyChanged;
if (pc != null)
pc(this, new PropertyChangedEventArgs(name));
}
public string PersonId
{
get { return _personId; }
set { _personId = value; OnPropertyChanged("PersonId"); }
}
public string City
{
get { return _city; }
set { _city = value; OnPropertyChanged("City"); }
}
}
public ObservableCollection<Person> Persons { get; set; }
public string GroupDescription
{
get { return _groupDescription; }
set { _groupDescription = value; OnPropertyChanged("GroupDescription"); }
}
private string _groupDescription;
public MainWindow()
{
InitializeComponent();
DataContext = this;
GroupDescription = "City";
Persons = new ObservableCollection<Person>();
Persons.CollectionChanged += PersonsCollectionChanged;
Persons.Add(new Person("1", "Hamburg"));
Persons.Add(new Person("2", "Hamburg"));
Persons.Add(new Person("3", "Hamburg"));
Persons.Add(new Person("4", "Hamburg"));
Persons.Add(new Person("5", "Hamburg"));
Persons.Add(new Person("6", "Hamburg"));
Persons.Add(new Person("7", "Hamburg"));
Persons.Add(new Person("8", "Hamburg"));
Persons.Add(new Person("9", "Berlin"));
Persons.Add(new Person("10", "Hamburg"));
Persons.Add(new Person("11", "Hamburg"));
Persons.Add(new Person("12", "Munich"));
Persons.Add(new Person("13", "Munich"));
OnPropertyChanged("Persons");
}
public void PersonsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Remove)
{
foreach(Person item in e.OldItems)
{
//Removed items
item.PropertyChanged -= PersonPropertyChanged;
}
}
else if (e.Action == NotifyCollectionChangedAction.Add)
{
foreach(Person item in e.NewItems)
{
//Added items
item.PropertyChanged += PersonPropertyChanged;
}
}
}
public void PersonPropertyChanged(object sender, PropertyChangedEventArgs e)
{
//GroupDescription = "PersonId";
//GroupDescription = "City";
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler pc = PropertyChanged;
if (pc != null)
pc(this, new PropertyChangedEventArgs(name));
}
private void btnChangeCity(object sender, System.Windows.RoutedEventArgs e)
{
Persons[0].City = "Berlin";
}
private void btnChangeCityBack(object sender, System.Windows.RoutedEventArgs e)
{
Persons[0].City = "Hamburg";
}
}
}