当绑定的可观察集合更改时,列表视图不会更新

本文关键字:列表 视图 更新 绑定 观察 集合 | 更新日期: 2023-09-27 18:30:36

我正在开发一个搜索窗口,该窗口将搜索结果加载到可观察集合中,然后使用列表视图显示结果。

在搜索完成后,将列表视图的 ItemSource 设置为"可观察集合"将正确填充列表。

我正在尝试让列表视图在搜索添加其他结果时更新,但列表视图根本没有填充任何数据。我无法弄清楚我的绑定在哪里掉落。

我的研究显示了使用 DataContext 的各种方法,但似乎没有一种帮助;我尝试使用CodeBehind以及在xaml窗口级别将其分配给"this"和我的CachedData类。

很抱歉代码片段很长,我留下了我认为可能有助于为问题添加上下文的任何内容。

XAML:

<Window x:Class="SLX_Interface.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:SLX_Interface"
    mc:Ignorable="d"
    Title="SLX Search" Height="auto" Width="auto">
<Window.CommandBindings>
</Window.CommandBindings>
<Grid>
    <Grid.Resources>
        <local:CachedData x:Key="cachedData" />
    </Grid.Resources>
    <TabControl x:Name="tabControl" Grid.RowSpan="2" Margin="0,20,0,0">
        <TabItem Header="Accounts" Name="accountsTab">
            <Grid>
                <ListView x:Name="accountSearchResultsListView" Margin="5,32,5,30" DataContext="staticResource cachedData" ItemsSource="{Binding Path=accounts}" IsSynchronizedWithCurrentItem="True">
                    <ListView.View>
                        <GridView x:Name="accountSearchResultsGridView">
                            <GridViewColumn Header="SData Key" DisplayMemberBinding="{Binding SDataKey}"/>
                            <GridViewColumn Header="Account Name" DisplayMemberBinding="{Binding AccountName}"/>
                        </GridView>
                    </ListView.View>
                </ListView>
             </Grid>
        </TabItem>
    </TabControl>
</Grid>

MainWindow.xaml.cs中的代码隐藏:

private async void SearchAccount(string searchTerm, string searchField, string searchOperator)
    {
        //Create the string we'll use for searching
        string urlString = "Stuff";
        //Create an ObservableCollection, then use it to blank the cache
        ObservableCollection<Account> resultsList = new ObservableCollection<Account>();
        CachedData.accounts = resultsList;
        //Getting data from the search using an XML Reader
        XmlReader resultsReader = null;
        try
        {
            //Using XmlReader to grab the search results from SLX
            XmlUrlResolver resultsResolver = new XmlUrlResolver();
            resultsResolver.Credentials = LoginCredentials.userCred;
            XmlReaderSettings resultsReaderSettings = new XmlReaderSettings();
            resultsReaderSettings.XmlResolver = resultsResolver;
            resultsReaderSettings.Async = true;
            resultsReader = XmlReader.Create(urlString, resultsReaderSettings);
        }
        catch (Exception error)
        {
        }
        //Grabbing data from the XML and storing it, hopefully updating the ListView as we go
        using (resultsReader)
        {
            while (await resultsReader.ReadAsync())
            {
                while (resultsReader.ReadToFollowing("slx:Account"))
                {
                    //Setting data from the XML to a new Account object ready to be passed to the list
                    Account account = new Account();
                    account.GUID = new Guid();
                    resultsReader.MoveToFirstAttribute(); account.SDataKey = resultsReader.Value;
                    resultsReader.ReadToFollowing("slx:AccountName"); account.AccountName = resultsReader.ReadElementContentAsString();
                    CachedData.accounts.Add(account);
                    //--Uncommenting this gives odd results;
                    //--The first item is displayed, any others aren't.
                    //--If there are a lot of items, the application eventually errors like mad and ends.
                    //--Looks like one error window for each item, though I don't see the message before they die along with the application.
                    //accountSearchResultsListView.ItemsSource = CachedData.accounts;
                }
            }
        }
        //--Uncommenting this works but shows the data once the entire XML has been read through, which can take some time so isn't ideal.
        //accountSearchResultsListView.ItemsSource = CachedData.accounts;        }

上面的类引用,存储在单独的.cs文件中,但在同一命名空间下:

public class CachedData
{
    public static ObservableCollection<Account> accounts { get; set; }
    public static event PropertyChangedEventHandler PropertyChanged;
    public static event EventHandler<PropertyChangedEventArgs> StaticPropertyChanged = delegate { };
    private static void NotifyStaticPropertyChanged(string propertyName)
    {
        StaticPropertyChanged(null, new PropertyChangedEventArgs(propertyName));
    }
}
public class Account : IEquatable<Account>
{
    public Guid GUID { get; set; }
    public string SDataKey { get; set; }
    public string AccountName { get; set; }
    public override string ToString()
    {
        return AccountName;
    }
    public override bool Equals(object obj)
    {
        if (obj == null) return false;
        Account objAsPart = obj as Account;
        if (objAsPart == null) return false;
        else return Equals(objAsPart);
    }
    public override int GetHashCode()
    {
        return 0;
    }
    public bool Equals(Account other)
    {
        if (other == null) return false;
        return (GUID.Equals(other.GUID));
    }
}

感谢您提供的任何帮助,这已经难倒了我好几天了。

当绑定的可观察集合更改时,列表视图不会更新

问题是您正在使用在内部实现INotifyCollectionChangedObservableCollection。 这不会引发对集合的每个更改。仅当在集合中添加或删除项目时,它才会引发集合更改。

因此,如果有人分配新的集合实例(如您的情况),就会出现问题。 因此,重置绑定并不是一个好的选择,相反,您可以自己提出更改。 通过简单地实现INotifyPropertyChanged。(通常情况)

public class DataClass : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    private ObservableCollection<string> collection;
    public ObservableCollection<string> Collection
    {
        get { return collection; }
        set
        {
            collection = value;
            OnPropertyChanged("Collection");
        }
    }       
}

因此,将集合分配给 null 或新实例也将反映到绑定控件。(您已经有 NotifyStaticPropertyChanged,您只需要创建一个完整的属性,并在需要时提出更改。

在 xaml 中设置数据绑定时,将绑定应用启动时存在的 ObservableCollection 实例。因此,请务必在应用启动之前实例化实例,并且不要将其替换为新实例,除非您在代码隐藏中重置数据绑定。如果需要清除其元素,请使用清除方法。