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[英]Listview doesn't update when the ObservableCollection its bound to changes
[英]ListView not updating when the bound ObservableCollection changes
我正在使用一个搜索窗口,它将搜索结果加载到ObservableCollection中,然后使用ListView显示结果。
搜索完成后,将ListView的ItemSource设置为ObservableCollection可以正确填充列表。
我正在尝试更新ListView,因为搜索添加了其他结果,但是ListView根本没有填充任何数据。 我无法解决我的绑定丢失的地方。
我的研究显示了使用DataContext的各种方法,尽管似乎没有帮助。 我尝试使用CodeBehind以及xaml Window级别将其分配给“ this”和CachedData类。
很抱歉,很长的代码片段,我遗漏了我认为可能有助于在问题中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>
从MainWindow.xaml.cs内部进行代码隐藏:
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,但在相同的名称空间下:
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));
}
}
我感谢您可以提供的任何帮助,这已经困扰了我好几天了。
在xaml中设置数据绑定时,将绑定应用程序启动时存在的ObservableCollection实例。 因此,请务必在应用启动之前实例化一个实例,并且不要用新实例替换它,除非您在后面的代码中重置了数据绑定。 如果需要清除其元素,请使用Clear方法。
问题是您使用的是内部实现INotifyCollectionChanged的 ObservableCollection 。 这并不会引起对收藏的任何改变。 仅当添加或从集合中删除项目时,它才会引发集合更改。
因此,如果有人分配一个新的collection实例( 视您的情况 ),将会发生问题。 因此重置绑定不是一个很好的选择,而是可以自己进行更改。 通过简单地实现INotifyPropertyChanged。(通常情况下)
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");
}
}
}
因此将集合分配为null或新实例也将反映到绑定控件中。 (您已经有了NotifyStaticPropertyChanged,您只需要创建一个完整的属性,并在需要时提出更改即可。)
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