UWP TreeView数据绑定和反映更改
UWP TreeView数据绑定和反映更改
提问于 2019-06-03 13:02:53
UWP TreeView是否通过从VM拖放到其关联的ItemsSource来反映项目的变化？例如，我将TreeView与VM ObservableCollection列表相关联。当我通过从VM执行命令来添加一些项，并用新项填充该集合时，它们确实显示在TreeView UI中。但是，如果我在TreeView内部拖放项目，基础列表不会改变吗？我做错了什么？TreeView是否应该根据我的操作更新和观察集合？
下面是我的虚拟机：
public class MySampleViewModel : MyBase
{
public ObservableCollection<FolderInfo> storageFolders { get; set; } = new ObservableCollection<FolderInfo>();
public ICommand MyCommand { get; }
public ICommand ChangeCommand { get; }
public MySampleViewModel()
{
AddFilesFolders();
}
private void AddFilesFolders()
{
FolderInfo ff1 = new FolderInfo();
ff1.FolderName = "Folder " + DateTime.Now.ToString();
ff1.IsFolder = true;
ff1.subFolders = new ObservableCollection<FolderInfo>();
storageFolders.Add(ff1);
FolderInfo ffkeko = new FolderInfo();
ffkeko.FolderName = "subitem" + DateTime.Now.ToString();
ffkeko.subFolders = new ObservableCollection<FolderInfo>();
ff1.subFolders.Add(ffkeko);
FolderInfo ff = new FolderInfo();
ff.FolderName = "servername " + DateTime.Now.ToString();
ff.subFolders = new ObservableCollection<FolderInfo>();
storageFolders.Add(ff);
}
}
public class MyBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged([CallerMemberName]string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
public class FolderInfo : MyBase
{
private string _FolderName;
public string FolderName
{
get { return _FolderName; }
set
{
if (_FolderName != value)
{
_FolderName = value;
OnPropertyChanged("FolderName");
}
}
}
private bool _IsFolder;
public bool IsFolder
{
get { return _IsFolder; }
set
{
if (_IsFolder != value)
{
_IsFolder = value;
OnPropertyChanged("IsFolder");
}
}
}
public ObservableCollection<FolderInfo> subFolders { get; set; } = new ObservableCollection<FolderInfo>();
public override string ToString()
{
return FolderName;
}
}下面是我针对TreeView的XAML：
<localdata:MyTreeView
x:Name="treeview" Grid.Row="2" ItemsSource="{Binding storageFolders,Mode=OneWay}"
Style="{StaticResource TreeViewStyle1}"
/>回答 1
Stack Overflow用户
发布于 2019-06-03 15:05:49
问题在于，当发生更改时，您实际上是将一个新的ObservableCollection<FolderInfo>实例分配给subFolders属性，但数据绑定被绑定到以前的实例，因此它不会观察到此更改。这个问题有两种解决方案：
1)更换实例并引发PropertyChanged事件：
private ObservableCollection<FolderInfo> _subFolders = new ObservableCollection<FolderInfo>();
public ObservableCollection<FolderInfo> subFolders
{
get => _subFolders;
set
{
_subFolders = value;
OnPropertyChanged();
}
}2)不分配新实例，清空原实例，只添加新项：
因此，不是：
ff.subFolders = new ObservableCollection<FolderInfo>();
ff.subFolders.Add(something);您将执行以下操作：
ff.subFolders.Clear();
ff.subFolders.Add(something);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/56427988
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