UWP 可观察集合排序和分组

我已经开始整理一个名为 GroupedObservableCollection 的库，它为我的一个应用程序做了一些类似的事情。

我需要解决的关键问题之一是刷新用于创建组的原始列表，即我不希望用户使用略有不同的条件进行搜索以刷新整个列表，只是差异。

以目前的形式，它现在可能无法回答您所有的排序问题，但对于其他人来说可能是一个很好的起点。

到目前为止尽最大努力使用以下帮助程序类 可观察分组集合

public class ObservableGroupingCollection<K, T> where K : IComparable
{
    public ObservableGroupingCollection(ObservableCollection<T> collection)
    {
        _rootCollection = collection;
        _rootCollection.CollectionChanged += _rootCollection_CollectionChanged;
    }
    ObservableCollection<T> _rootCollection;
    private void _rootCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        HandleCollectionChanged(e);
    }
    ObservableCollection<Grouping<K, T>> _items;
    public ObservableCollection<Grouping<K, T>> Items
    {
        get { return _items; }
    }
    IComparer<T> _sortOrder;
    Func<T, K> _groupFunction;
    public void ArrangeItems(IComparer<T> sortorder, Func<T, K> group)
    {
        _sortOrder = sortorder;
        _groupFunction = group;
        var temp = _rootCollection
            .OrderBy(i => i, _sortOrder)
            .GroupBy(_groupFunction)
            .ToList()
            .Select(g => new Grouping<K, T>(g.Key, g));
        _items = new ObservableCollection<Grouping<K, T>>(temp);
    }
    private void HandleCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == NotifyCollectionChangedAction.Add)
        {
            var item = (T)(e.NewItems[0]);
            var value = _groupFunction.Invoke(item);
            // find matching group if exists
            var existingGroup = _items.FirstOrDefault(g => g.Key.Equals(value));
            if (existingGroup == null)
            {
                var newlist = new List<T>();
                newlist.Add(item);
                // find first group where Key is greater than this key
                var insertBefore = _items.FirstOrDefault(g => ((g.Key).CompareTo(value)) > 0);
                if (insertBefore == null)
                {
                    // not found - add new group to end of list
                    _items.Add(new Grouping<K, T>(value, newlist));
                }
                else
                {
                    // insert new group at this index
                    _items.Insert(_items.IndexOf(insertBefore), new Grouping<K, T>(value, newlist));
                }
            }
            else
            {
                // find index to insert new item in existing group
                int index = existingGroup.ToList().BinarySearch(item, _sortOrder);
                if (index < 0)
                {
                    existingGroup.Insert(~index, item);
                }
            }
        }
        else if (e.Action == NotifyCollectionChangedAction.Remove)
        {
            var item = (T)(e.OldItems[0]);
            var value = _groupFunction.Invoke(item);
            var existingGroup = _items.FirstOrDefault(g => g.Key.Equals(value));
            if (existingGroup != null)
            {
                // find existing item and remove
                var targetIndex = existingGroup.IndexOf(item);
                existingGroup.RemoveAt(targetIndex);
                // remove group if zero items
                if (existingGroup.Count == 0)
                {
                    _items.Remove(existingGroup);
                }
            }
        }
    }
}

其中泛型分组类（它本身公开了一个 ObservableCollection）来自本文

http://motzcod.es/post/94643411707/enhancing-xamarinforms-listview-with-grouping

制作工作演示：-

从新的 UWP 空白应用程序中，添加上述可观察分组集合类。然后在同一命名空间中添加另一个类文件并添加所有后续类

// Data models
public class Contact
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string State { get; set; }
}
public class DataPool
{
    public static string GenerateFirstName(Random random)
    {
        List<string> names = new List<string>() { "Lilly", "Mukhtar", "Sophie", "Femke", "Abdul-Rafi", "Mariana", "Aarif", "Sara", "Ibadah", "Fakhr", "Ilene", "Sardar", "Hanna", "Julie", "Iain", "Natalia", "Henrik", "Rasa", "Quentin", "Gadi", "Pernille", "Ishtar", "Jimmy", "Justine", "Lale", "Elize", "Randy", "Roshanara", "Rajab", "Marcus", "Mark", "Alima", "Francisco", "Thaqib", "Andreas", "Marianna", "Amalie", "Rodney", "Dena", "Amar", "Anna", "Nasreen", "Reema", "Tomas", "Filipa", "Frank", "Bari'ah", "Parvaiz", "Jibran", "Tomas", "Elli", "Carlos", "Diego", "Henrik", "Aruna", "Vahid", "Eliana", "Roxanne", "Amanda", "Ingrid", "Wesley", "Malika", "Basim", "Eisa", "Alina", "Andreas", "Deeba", "Diya", "Parveen", "Bakr", "Celine", "Daniel", "Mattheus", "Edmee", "Hedda", "Maria", "Maja", "Alhasan", "Alina", "Hedda", "Vanja", "Robin", "Victor", "Aaftab", "Guilherme", "Maria", "Kai", "Sabien", "Abdel", "Jason", "Bahaar", "Vasco", "Jibran", "Parsa", "Catalina", "Fouad", "Colette", "John", "Fred", "James", "Harry", "Ben", "Steven", "Philip", "Dougal", "Jasper", "Elliott", "Charles", "Gerty", "Sarah", "Sonya", "Svetlana", "Dita", "Karen", "Christine", "Angela", "Heather", "Spence", "Graham", "David", "Bernie", "Darren", "Lester", "Vince", "Colin", "Bernhard", "Dieter", "Norman", "William", "Nigel", "Nick", "Nikki", "Trent", "Devon", "Steven", "Eric", "Derek", "Raymond", "Craig" };
        return names[random.Next(0, names.Count)];
    }
    public static string GenerateLastName(Random random)
    {
        List<string> lastnames = new List<string>() { "Carlson", "Attia", "Quincey", "Hollenberg", "Khoury", "Araujo", "Hakimi", "Seegers", "Abadi", "Krommenhoek", "Siavashi", "Kvistad", "Vanderslik", "Fernandes", "Dehmas", "Sheibani", "Laamers", "Batlouni", "Lyngvær", "Oveisi", "Veenhuizen", "Gardenier", "Siavashi", "Mutlu", "Karzai", "Mousavi", "Natsheh", "Nevland", "Lægreid", "Bishara", "Cunha", "Hotaki", "Kyvik", "Cardoso", "Pilskog", "Pennekamp", "Nuijten", "Bettar", "Borsboom", "Skistad", "Asef", "Sayegh", "Sousa", "Miyamoto", "Medeiros", "Kregel", "Shamoun", "Behzadi", "Kuzbari", "Ferreira", "Barros", "Fernandes", "Xuan", "Formosa", "Nolette", "Shahrestaani", "Correla", "Amiri", "Sousa", "Fretheim", "Van", "Hamade", "Baba", "Mustafa", "Bishara", "Formo", "Hemmati", "Nader", "Hatami", "Natsheh", "Langen", "Maloof", "Patel", "Berger", "Ostrem", "Bardsen", "Kramer", "Bekken", "Salcedo", "Holter", "Nader", "Bettar", "Georgsen", "Cuninho", "Zardooz", "Araujo", "Batalha", "Antunes", "Vanderhoorn", "Srivastava", "Trotter", "Siavashi", "Montes", "Sherzai", "Vanderschans", "Neves", "Sarraf", "Kuiters", "Hestoe", "Cornwall", "Paisley", "Cooper", "Jakoby", "Smith", "Davies", "Jonas", "Bowers", "Fernandez", "Perez", "Black", "White", "Keller", "Hernandes", "Clinton", "Merryweather", "Freeman", "Anguillar", "Goodman", "Hardcastle", "Emmott", "Kirkby", "Thatcher", "Jamieson", "Spender", "Harte", "Pinkman", "Winterman", "Knight", "Taylor", "Wentworth", "Manners", "Walker", "McPherson", "Elder", "McDonald", "Macintosh", "Decker", "Takahashi", "Wagoner" };
        return lastnames[random.Next(0, lastnames.Count)];
    }
    public static string GenerateState(Random random)
    {
        List<string> states = new List<string>() { "Alabama", "Alaska", "Arizona", "Arkansas", "California", "Colorado", "Connecticut", "Delaware", "District Of Columbia", "Florida", "Georgia", "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas", "Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts", "Michigan", "Minnesota", "Mississippi", "Missouri", "Montana", "Nebraska", "Nevada", "New Hampshire", "New Jersey", "New Mexico", "New York", "North Carolina", "North Dakota", "Ohio", "Oklahoma", "Oregon", "Pennsylvania", "Rhode Island", "South Carolina", "South Dakota", "Tennessee", "Texas", "Utah", "Vermont", "Virginia", "Washington", "West Virginia", "Wisconsin", "Wyoming" };
        return states[random.Next(0, states.Count)];
    }
}
public class Cache
{
    public Cache()
    {
        InitializeCacheData();
        SimulateLiveChanges(new TimeSpan(0, 0, 1));
    }
    public ObservableCollection<Contact> Contacts { get; set; }
    private static Random rnd = new Random();
    private void InitializeCacheData()
    {
        Contacts = new ObservableCollection<Contact>();
        var i = 0;
        while (i < 5)
        {
            Contacts.Add(new Contact()
            {
                FirstName = DataPool.GenerateFirstName(rnd),
                LastName = DataPool.GenerateLastName(rnd),
                State = DataPool.GenerateState(rnd)
            });
            i++;
        }
    }
    private async void SimulateLiveChanges(TimeSpan MyInterval)
    {
        double MyIntervalSeconds = MyInterval.TotalSeconds;
        while (true)
        {
            await Task.Delay(MyInterval);
            //int addOrRemove = rnd.Next(1, 10);
            //if (addOrRemove > 3)
            //{
            // add item
            Contacts.Add(new Contact()
            {
                FirstName = DataPool.GenerateFirstName(rnd),
                LastName = DataPool.GenerateLastName(rnd),
                State = DataPool.GenerateState(rnd)
            });
            //}
            //else
            //{
            //    // remove random item
            //    if (Contacts.Count > 0)
            //    {
            //        Contacts.RemoveAt(rnd.Next(0, Contacts.Count - 1));
            //    }
            //}
        }
    }
}
// ViewModel
public class ViewModel : BaseViewModel
{       
    public ViewModel()
    {
        _groupingCollection = new ObservableGroupingCollection<string, Contact>(new Cache().Contacts);
        _groupingCollection.ArrangeItems(new StateSorter(), (x => x.State));
        NotifyPropertyChanged("GroupedContacts");
    }
    ObservableGroupingCollection<string, Contact> _groupingCollection;
    public ObservableCollection<Grouping<string, Contact>> GroupedContacts
    {
        get
        {
            return _groupingCollection.Items;
        }
    }
    // swap grouping commands
    private ICommand _groupByStateCommand;
    public ICommand GroupByStateCommand
    {
        get
        {
            if (_groupByStateCommand == null)
            {
                _groupByStateCommand = new RelayCommand(
                    param => GroupByState(),
                    param => true);
            }
            return _groupByStateCommand;
        }
    }
    private void GroupByState()
    {
        _groupingCollection.ArrangeItems(new StateSorter(), (x => x.State));
        NotifyPropertyChanged("GroupedContacts");
    }
    private ICommand _groupByNameCommand;
    public ICommand GroupByNameCommand
    {
        get
        {
            if (_groupByNameCommand == null)
            {
                _groupByNameCommand = new RelayCommand(
                    param => GroupByName(),
                    param => true);
            }
            return _groupByNameCommand;
        }
    }
    private void GroupByName()
    {
        _groupingCollection.ArrangeItems(new NameSorter(), (x => x.LastName.First().ToString()));
        NotifyPropertyChanged("GroupedContacts");
    }
}
// View Model helpers
public class BaseViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}
public class RelayCommand : ICommand
{
    readonly Action<object> _execute;
    readonly Predicate<object> _canExecute;
    public RelayCommand(Action<object> execute)
        : this(execute, null)
    {
    }
    public RelayCommand(Action<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");
        _execute = execute;
        _canExecute = canExecute;
    }
    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute(parameter);
    }
    public event EventHandler CanExecuteChanged
    {
        add { } 
        remove { } 
    }
    public void Execute(object parameter)
    {
        _execute(parameter);
    }
}
// Sorter classes
public class NameSorter : Comparer<Contact>
{
    public override int Compare(Contact x, Contact y)
    {
        int result = x.LastName.First().CompareTo(y.LastName.First());
        if (result != 0)
        {
            return result;
        }
        else
        {
            result = x.LastName.CompareTo(y.LastName);
            if (result != 0)
            {
                return result;
            }
            else
            {
                return x.FirstName.CompareTo(y.FirstName);
            }
        }
    }
}
public class StateSorter : Comparer<Contact>
{
    public override int Compare(Contact x, Contact y)
    {
        int result = x.State.CompareTo(y.State);
        if (result != 0)
        {
            return result;
        }
        else
        {
            result = x.LastName.CompareTo(y.LastName);
            if (result != 0)
            {
                return result;
            }
            else
            {
                return x.FirstName.CompareTo(y.FirstName);
            }
        }
    }
}
// Grouping class 
// credit
// http://motzcod.es/post/94643411707/enhancing-xamarinforms-listview-with-grouping
public class Grouping<K, T> : ObservableCollection<T>
{
    public K Key { get; private set; }
    public Grouping(K key, IEnumerable<T> items)
    {
        Key = key;
        foreach (var item in items)
        {
            this.Items.Add(item);
        }
    }
}

最后，按如下方式编辑主页

  <Page.DataContext>
        <local:ViewModel />
    </Page.DataContext>
    <Page.Resources>
        <CollectionViewSource 
            x:Key="cvs" 
            Source="{Binding GroupedContacts}" 
            IsSourceGrouped="True" />
    </Page.Resources>
    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <ListView ItemsSource="{Binding Source={StaticResource cvs}}"
                  x:Name="targetListBox">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="100" />
                            <ColumnDefinition Width="100" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <TextBlock Text="{Binding LastName}" />
                        <TextBlock Text="{Binding FirstName}" Grid.Column="1" />
                        <TextBlock Text="{Binding State}" Grid.Column="2" HorizontalAlignment="Right" />
                    </Grid>
                </DataTemplate>
            </ListView.ItemTemplate>
            <ListView.GroupStyle>
                <GroupStyle>
                    <GroupStyle.HeaderTemplate>
                        <DataTemplate>
                            <Grid Background="Gainsboro">
                                <TextBlock FontWeight="Bold" 
                                           FontSize="14" 
                                           Margin="10,2"
                                           Text="{Binding Key}"/>
                            </Grid>
                        </DataTemplate>
                    </GroupStyle.HeaderTemplate>
                </GroupStyle>
            </ListView.GroupStyle>
        </ListView>
        <StackPanel Orientation="Horizontal" Grid.Row="1">
            <Button Content="Group By Initial" Command="{Binding GroupByNameCommand}" />
            <Button Content="Group By State" Command="{Binding GroupByStateCommand}" />
        </StackPanel>
    </Grid>

HandleCollectionChanged 方法到目前为止仅处理添加/删除，如果 NotifyCollectionChangedEventArgs 参数包含多个项目，则会分解（现有 ObservableCollection 类一次只通知一个更改）

所以它工作正常，但感觉有点笨拙。

非常欢迎改进建议。