一度に1つのツリービューと1つのドキュメントを表示するために、この問題を解決しました。このソリューションは、通常のツリービューにアタッチできるアタッチ可能な動作に基づいています。
<TreeView Grid.Column="0"
ItemsSource="{Binding TreeViewItems}"
behav:TreeViewSelectionChangedBehavior.ChangedCommand="{Binding SelectItemChangedCommand}"
>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Children}">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Name}"
ToolTipService.ShowOnDisabled="True"
VerticalAlignment="Center" Margin="3" />
</StackPanel>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
動作のコードは次のとおりです。
/// <summary>
/// Source:
/// http://stackoverflow.com/questions/1034374/drag-and-drop-in-mvvm-with-scatterview
/// http://social.msdn.microsoft.com/Forums/de-DE/wpf/thread/21bed380-c485-44fb-8741-f9245524d0ae
///
/// Attached behaviour to implement the SelectionChanged command/event via delegate command binding or routed commands.
/// </summary>
public static class TreeViewSelectionChangedBehavior
{
#region fields
/// <summary>
/// Field of attached ICommand property
/// </summary>
private static readonly DependencyProperty ChangedCommandProperty = DependencyProperty.RegisterAttached(
"ChangedCommand",
typeof(ICommand),
typeof(TreeViewSelectionChangedBehavior),
new PropertyMetadata(null, OnSelectionChangedCommandChange));
/// <summary>
/// Implement backing store for UndoSelection dependency proeprty to indicate whether selection should be
/// cancelled via MessageBox query or not.
/// </summary>
public static readonly DependencyProperty UndoSelectionProperty =
DependencyProperty.RegisterAttached("UndoSelection",
typeof(bool),
typeof(TreeViewSelectionChangedBehavior),
new PropertyMetadata(false, OnUndoSelectionChanged));
#endregion fields
#region methods
#region ICommand changed methods
/// <summary>
/// Setter method of the attached ChangedCommand <seealso cref="ICommand"/> property
/// </summary>
/// <param name="source"></param>
/// <param name="value"></param>
public static void SetChangedCommand(DependencyObject source, ICommand value)
{
source.SetValue(ChangedCommandProperty, value);
}
/// <summary>
/// Getter method of the attached ChangedCommand <seealso cref="ICommand"/> property
/// </summary>
/// <param name="source"></param>
/// <returns></returns>
public static ICommand GetChangedCommand(DependencyObject source)
{
return (ICommand)source.GetValue(ChangedCommandProperty);
}
#endregion ICommand changed methods
#region UndoSelection methods
public static bool GetUndoSelection(DependencyObject obj)
{
return (bool)obj.GetValue(UndoSelectionProperty);
}
public static void SetUndoSelection(DependencyObject obj, bool value)
{
obj.SetValue(UndoSelectionProperty, value);
}
#endregion UndoSelection methods
/// <summary>
/// This method is hooked in the definition of the <seealso cref="ChangedCommandProperty"/>.
/// It is called whenever the attached property changes - in our case the event of binding
/// and unbinding the property to a sink is what we are looking for.
/// </summary>
/// <param name="d"></param>
/// <param name="e"></param>
private static void OnSelectionChangedCommandChange(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TreeView uiElement = d as TreeView; // Remove the handler if it exist to avoid memory leaks
if (uiElement != null)
{
uiElement.SelectedItemChanged -= Selection_Changed;
var command = e.NewValue as ICommand;
if (command != null)
{
// the property is attached so we attach the Drop event handler
uiElement.SelectedItemChanged += Selection_Changed;
}
}
}
/// <summary>
/// This method is called when the selection changed event occurs. The sender should be the control
/// on which this behaviour is attached - so we convert the sender into a <seealso cref="UIElement"/>
/// and receive the Command through the <seealso cref="GetChangedCommand"/> getter listed above.
///
/// The <paramref name="e"/> parameter contains the standard EventArgs data,
/// which is unpacked and reales upon the bound command.
///
/// This implementation supports binding of delegate commands and routed commands.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private static void Selection_Changed(object sender, RoutedPropertyChangedEventArgs<object> e)
{
var uiElement = sender as TreeView;
// Sanity check just in case this was somehow send by something else
if (uiElement == null)
return;
ICommand changedCommand = TreeViewSelectionChangedBehavior.GetChangedCommand(uiElement);
// There may not be a command bound to this after all
if (changedCommand == null)
return;
// Check whether this attached behaviour is bound to a RoutedCommand
if (changedCommand is RoutedCommand)
{
// Execute the routed command
(changedCommand as RoutedCommand).Execute(e.NewValue, uiElement);
}
else
{
// Execute the Command as bound delegate
changedCommand.Execute(e.NewValue);
}
}
/// <summary>
/// Executes when the bound boolean property indicates that a user should be asked
/// about changing a treeviewitem selection instead of just performing it.
/// </summary>
/// <param name="d"></param>
/// <param name="e"></param>
private static void OnUndoSelectionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TreeView uiElement = d as TreeView; // Remove the handler if it exist to avoid memory leaks
if (uiElement != null)
{
uiElement.PreviewMouseDown -= uiElement_PreviewMouseDown;
var command = (bool)e.NewValue;
if (command == true)
{
// the property is attached so we attach the Drop event handler
uiElement.PreviewMouseDown += uiElement_PreviewMouseDown;
}
}
}
/// <summary>
/// Based on the solution proposed here:
/// Source: http://stackoverflow.com/questions/20244916/wpf-treeview-selection-change
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private static void uiElement_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
// first did the user click on a tree node?
var source = e.OriginalSource as DependencyObject;
while (source != null && !(source is TreeViewItem))
source = VisualTreeHelper.GetParent(source);
var itemSource = source as TreeViewItem;
if (itemSource == null)
return;
var treeView = sender as TreeView;
if (treeView == null)
return;
bool undoSelection = TreeViewSelectionChangedBehavior.GetUndoSelection(treeView);
if (undoSelection == false)
return;
// Cancel the attempt to select an item.
var result = MessageBox.Show("The current document has unsaved data. Do you want to continue without saving data?", "Are you really sure?",
MessageBoxButton.YesNo, MessageBoxImage.Question, MessageBoxResult.No);
if (result == MessageBoxResult.No)
{
// Cancel the attempt to select a differnet item.
e.Handled = true;
}
else
{
// Lets disable this for a moment, otherwise, we'll get into an event "recursion"
treeView.PreviewMouseDown -= uiElement_PreviewMouseDown;
// Select the new item - make sure a SelectedItemChanged event is fired in any case
// Even if this means that we have to deselect/select the one and the same item
if (itemSource.IsSelected == true )
itemSource.IsSelected = false;
itemSource.IsSelected = true;
// Lets enable this to get back to business for next selection
treeView.PreviewMouseDown += uiElement_PreviewMouseDown;
}
}
#endregion methods
}
この例では、発生時に PreviewMouseDown イベントをブロックするためにブロック メッセージ ボックスを表示しています。次に、選択が取り消されたことを通知するためにイベントが処理されるか、選択されようとしている項目を選択することによってツリービュー自体がイベントを処理できるようにするために処理されません。
ユーザーがとにかく続行することを決定した場合、ビヘイビアはビューモデルでバインドされたコマンドを呼び出します (PreviewMouseDown イベントは添付されたビヘイビアによって処理されず、バインドされたコマンドが呼び出されます。
メッセージボックスの表示は他の方法でもできると思いますが、イベントが発生したときにイベントをブロックすることが不可欠だと思います。そうしないとキャンセルできないからです(?)。したがって、このコードについて考えられる唯一の改善点は、いくつかの文字列をバインドして、表示されるメッセージを構成可能にすることです。
ダウンロード可能なサンプルを含む記事を書きましたが、それ以外の場合は説明が難しいためです (不足している部分について多くの仮定を立てる必要があり、すべての読者が常に共有しているとは限りません)。
これが私の結果を含む記事です:
http://www.codeproject.com/Articles/995629/Cancelable-TreeView-Navigation-for-Documents-in-WP
この解決策についてコメントし、改善の余地があればお知らせください。
