绑定属性更改时，ListView分组不会更新 [英] ListView Grouping does not update when bound property is changed
问题描述
我正在使用依赖项属性GroupDescription根据我的列表视图项源的属性对WPF列表视图中的项进行分组。
I am using a dependency property GroupDescription to group items within a WPF list view according to a property of my list views items source.
我的问题是分组仅在更改GroupDescription值时更新，而不是在列表视图源中的项目的绑定属性更改后才更新。
My problem is that the grouping is only updated if the GroupDescription value is changed and not once the bound property of an item within the list views source is changed.
在此示例中，GroupDescription设置为导致对城市：汉堡进行分组描述的城市。但是，当更改项目城市属性时，列表视图中的分组不会更新，这意味着在城市：汉堡组中将存在一个具有柏林城市的项目。
In this example below the GroupDescription is set to city which results in a group description of "City: Hamburg". But when an items city property is changed the grouping within the list view is not updated which means that there will be an item with City "Berlin" within the group "City: Hamburg".
仅在更新GroupDescription后更新分组。我试图找到一种使用PersonPropertyChanged方法的方法，该方法将GroupDescription更改为PersonId并立即返回到City。但是，这种解决方法会使列表视图始终跳回到顶部，以防万一滚动位置位于列表视图的中间或结尾。当使用具有更改属性的数百个条目的列表视图时，这确实很烦人。
The grouping is only updated once the GroupDescription is updated. I tried to find a work around using the PersonPropertyChanged method which changes the GroupDescription to PersonId and immediately back to City. However this work around results in the list view always jumping back to the top in case the scroll position was for example in the middle or at the end of the listview. This can be really annoying when working with a list view with hundres of entries with changing properties.
是否有一种方法可以在项目属性更改后更新分组没有列表视图跳回到顶部？
Is there a way I can "update" the grouping after an items property changed without the list view jumping back to the top?
在此先感谢您的帮助！
Thomas
Thank you in advance for any help! Thomas
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";
}
}
}
推荐答案
我自己找到了一个可行的解决方案。
I found a working solution myself.
在我调用的PersonPropertyChanged方法内
Within the PersonPropertyChanged method I call
ICollectionView view = CollectionViewSource.GetDefaultView(GroupingListView.ItemsSource);
view.Refresh();
我不确定这是否是完美的解决方案，但是否可以解决我的问题。
I am not sure if this is the perfect solution but it is working for my problem.
这篇关于绑定属性更改时，ListView分组不会更新的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
