Mvvm 更改ObservableCollection时，FlowListView未完全更新UI<；T>；

当我从列表中删除对象时，UI不会反映列表的当前状态，通常只有一个项目出现故障

示例：如果我删除了4项，则在UI上仅显示我删除了3项

 private ObservableCollection<Card> _cards;

    public ObservableCollection<Card> Cards
    {
        get
        {
            if (_cards == null)
            {
                _cards = new ObservableCollection<Card>();
                return _cards;
            }

            return _cards;
        }
        set
        {
            SetValue(ref _cards, value);
        }
    }

我在FlowListView中的绑定

<controls:FlowListView x:Name="Board" HasUnevenRows="True"
                               BackgroundColor="Black"
                               FlowColumnCount="2"
                               FlowItemTappedCommand="{Binding ExecuteActionCommand}"
                               FlowColumnMinWidth="110"
                               IsPullToRefreshEnabled="True"
                               IsRefreshing="{Binding IsRefreshing}"
                               RefreshCommand="{Binding RefreshViewCommand}"
                               FlowItemsSource="{Binding Cards}"> .....

。。。。。

---

提前感谢各位

请确保在property语句中的SetValue（）之后正确触发PropertyChanged

及

尝试使用这个类（来自xamarin）并传递card的ienumerable，而不是card-only对象

范例

private void RemoveFromCards(Card card)
{
    Cards.RemoveRange(new []{card});
}

//or directly from

private void RemoveCardsFromView(List<Archive> cards)
{
    Cards.RemoveRange(cards.Select(s=> new Card {Id = a.CardId}));
} 

/// <summary> 
/// Represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed. 
/// </summary> 
/// <typeparam name="T"></typeparam> 
public class ObservableRangeCollection<T> : ObservableCollection<T>
{

    /// <summary> 
    /// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class. 
    /// </summary> 
    public ObservableRangeCollection()
        : base()
    {
    }

    /// <summary> 
    /// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class that contains elements copied from the specified collection. 
    /// </summary> 
    /// <param name="collection">collection: The collection from which the elements are copied.</param> 
    /// <exception cref="System.ArgumentNullException">The collection parameter cannot be null.</exception> 
    public ObservableRangeCollection(IEnumerable<T> collection)
        : base(collection)
    {
    }

    /// <summary> 
    /// Adds the elements of the specified collection to the end of the ObservableCollection(Of T). 
    /// </summary> 
    public void AddRange(IEnumerable<T> collection, NotifyCollectionChangedAction notificationMode = NotifyCollectionChangedAction.Add)
    {
        if (collection == null)
            throw new ArgumentNullException("collection");

        CheckReentrancy();

        if (notificationMode == NotifyCollectionChangedAction.Reset)
        {
            foreach (var i in collection)
            {
                Items.Add(i);
            }

            OnPropertyChanged(new PropertyChangedEventArgs("Count"));
            OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));

            return;
        }

        int startIndex = Count;
        var changedItems = collection is List<T> ? (List<T>)collection : new List<T>(collection);
        foreach (var i in changedItems)
        {
            Items.Add(i);
        }

        OnPropertyChanged(new PropertyChangedEventArgs("Count"));
        OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, changedItems, startIndex));
    }

    /// <summary> 
    /// Removes the first occurence of each item in the specified collection from ObservableCollection(Of T). 
    /// </summary> 
    public void RemoveRange(IEnumerable<T> collection)
    {
        if (collection == null)
            throw new ArgumentNullException("collection");

        foreach (var i in collection)
            Items.Remove(i);
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }

    /// <summary> 
    /// Clears the current collection and replaces it with the specified item. 
    /// </summary> 
    public void Replace(T item)
    {
        ReplaceRange(new T[] { item });
    }

    /// <summary> 
    /// Clears the current collection and replaces it with the specified collection. 
    /// </summary> 
    public void ReplaceRange(IEnumerable<T> collection)
    {
        if (collection == null)
            throw new ArgumentNullException("collection");

        Items.Clear();
        AddRange(collection, NotifyCollectionChangedAction.Reset);
    }
}

private void RemoveFromCards（卡片）
{
Cards.RemoveRange（新[]{card}）；
}
//或者直接从
私有作废移除卡片浏览（列表卡）
{
Cards.RemoveRange（Cards.Select（s=>newcard{Id=a.cardd}））；
} 
///  
///表示动态数据集合，该集合在添加、删除项或刷新整个列表时提供通知。
///  
///  
公共类ObserverAgeCollection:ObserverCollection
{
///  
///初始化System.Collections.ObjectModel.ObservableCollection（of T）类的新实例。
///  
公共ObserverAgeCollection（）
：base（）
{
}
///  
///初始化System.Collections.ObjectModel.ObservableCollection（of T）类的新实例，该类包含从指定集合复制的元素。
///  
///集合：从中复制元素的集合。
///集合参数不能为null。
公共ObserverAgeCollection（IEnumerable集合）
：基本（集合）
{
}
///  
///将指定集合的元素添加到ObservableCollection（of T）的末尾。
///  
public void AddRange（IEnumerable集合，NotifyCollectionChangedAction notificationMode=NotifyCollectionChangedAction.Add）
{
if（集合==null）
抛出新的ArgumentNullException（“集合”）；
检查可重入性（）；
if（notificationMode==NotifyCollectionChangedAction.Reset）
{
foreach（集合中的变量i）
{
项目.添加（i）；
}
OnPropertyChanged（新PropertyChangedEventArgs（“计数”）；
OnPropertyChanged（新的PropertyChangedEventArgs（“项目[]”）；
OnCollectionChanged（新建NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Reset））；
返回；
}
int startIndex=计数；
var changedItems=集合是列表？（列表）集合：新列表（集合）；
foreach（changedItems中的变量i）
{
项目.添加（i）；
}
OnPropertyChanged（新PropertyChangedEventArgs（“计数”）；
OnPropertyChanged（新的PropertyChangedEventArgs（“项目[]”）；
OnCollectionChanged（新的NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Add、changedItems、startIndex））；
}
///  
///从ObservableCollection（of T）中删除指定集合中每个项的第一次出现。
///  
公共无效删除范围（IEnumerable集合）
{
if（集合==null）
抛出新的ArgumentNullException（“集合”）；
foreach（集合中的变量i）
删除第（i）项；
OnCollectionChanged（新建NotifyCollectionChangedEventArgs（NotifyCollectionChangedAction.Reset））；
}
///  
///清除当前集合并将其替换为指定项。
///  
公共无效替换（T项）
{
替换范围（新的T[]{item}）；
}
///  
///清除当前集合并将其替换为指定集合。
///  
公共void ReplaceRange（IEnumerable集合）
{
if（集合==null）
抛出新的ArgumentNullException（“集合”）；
Items.Clear（）；
AddRange（collection，NotifyCollectionChangedAction.Reset）；
}
}

如何计算“RemoveCardsFromView”函数中的参数“cards”？输入你的电话号码please@safi我就是这么叫它的。每个归档文件都有一个Id引用，指向ObservableCollections上的卡。请记住，此错误并非总是发生。老实说，我不知道这次可观测到的数据是怎么回事。我的猜测是FlowListView中的绑定有问题，但我搜索了他们的论坛，似乎并没有人给出答案，我会试试。你能告诉我这个类和ObservableCollection在被通知方面有什么区别吗？Items.Remove（i）对我不起作用，它与比较有关。这就是为什么我在自己做比较时使用RemoveAt（索引）的原因我知道，但是在那次更改之后，代码在其他地方开始崩溃，我放弃了这个想法，自己做了比较。我将尝试againI多次尝试测试它，当我删除1个元素时，它有2个元素时，项目会得到更新，但UI仍保留2个元素

 public async Task RefreshCardsView()
    {
        if (!CrossConnectivity.Current.IsConnected)
        {
            BuildToast(false,"No internet connection");
            return;
        }

        try
        {
            JsonResult cards = (JsonResult) await HttpMiddleman.GetCards();
            RemoveCardsFromView(cards.Data.DeletedCards);
            AddCardsToView(cards.Data.AddedCards);
        }
        catch (Exception e)
        {
            Debug.WriteLine(e.Message);
            BuildToast(false,"Could not refresh");
        }               
    }

<controls:FlowListView x:Name="Board" HasUnevenRows="True"
                               BackgroundColor="Black"
                               FlowColumnCount="2"
                               FlowItemTappedCommand="{Binding ExecuteActionCommand}"
                               FlowColumnMinWidth="110"
                               IsPullToRefreshEnabled="True"
                               IsRefreshing="{Binding IsRefreshing}"
                               RefreshCommand="{Binding RefreshViewCommand}"
                               FlowItemsSource="{Binding Cards}"> .....

private void RemoveFromCards(Card card)
{
    Cards.RemoveRange(new []{card});
}

//or directly from

private void RemoveCardsFromView(List<Archive> cards)
{
    Cards.RemoveRange(cards.Select(s=> new Card {Id = a.CardId}));
} 

/// <summary> 
/// Represents a dynamic data collection that provides notifications when items get added, removed, or when the whole list is refreshed. 
/// </summary> 
/// <typeparam name="T"></typeparam> 
public class ObservableRangeCollection<T> : ObservableCollection<T>
{

    /// <summary> 
    /// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class. 
    /// </summary> 
    public ObservableRangeCollection()
        : base()
    {
    }

    /// <summary> 
    /// Initializes a new instance of the System.Collections.ObjectModel.ObservableCollection(Of T) class that contains elements copied from the specified collection. 
    /// </summary> 
    /// <param name="collection">collection: The collection from which the elements are copied.</param> 
    /// <exception cref="System.ArgumentNullException">The collection parameter cannot be null.</exception> 
    public ObservableRangeCollection(IEnumerable<T> collection)
        : base(collection)
    {
    }

    /// <summary> 
    /// Adds the elements of the specified collection to the end of the ObservableCollection(Of T). 
    /// </summary> 
    public void AddRange(IEnumerable<T> collection, NotifyCollectionChangedAction notificationMode = NotifyCollectionChangedAction.Add)
    {
        if (collection == null)
            throw new ArgumentNullException("collection");

        CheckReentrancy();

        if (notificationMode == NotifyCollectionChangedAction.Reset)
        {
            foreach (var i in collection)
            {
                Items.Add(i);
            }

            OnPropertyChanged(new PropertyChangedEventArgs("Count"));
            OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));

            return;
        }

        int startIndex = Count;
        var changedItems = collection is List<T> ? (List<T>)collection : new List<T>(collection);
        foreach (var i in changedItems)
        {
            Items.Add(i);
        }

        OnPropertyChanged(new PropertyChangedEventArgs("Count"));
        OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, changedItems, startIndex));
    }

    /// <summary> 
    /// Removes the first occurence of each item in the specified collection from ObservableCollection(Of T). 
    /// </summary> 
    public void RemoveRange(IEnumerable<T> collection)
    {
        if (collection == null)
            throw new ArgumentNullException("collection");

        foreach (var i in collection)
            Items.Remove(i);
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }

    /// <summary> 
    /// Clears the current collection and replaces it with the specified item. 
    /// </summary> 
    public void Replace(T item)
    {
        ReplaceRange(new T[] { item });
    }

    /// <summary> 
    /// Clears the current collection and replaces it with the specified collection. 
    /// </summary> 
    public void ReplaceRange(IEnumerable<T> collection)
    {
        if (collection == null)
            throw new ArgumentNullException("collection");

        Items.Clear();
        AddRange(collection, NotifyCollectionChangedAction.Reset);
    }
}