在我阅读this article后，我决定使用VirtualToggleButton并添加两个布尔属性SuppressKeyboard和SuppressMouse来定义是否应将e.Handled设置为True。
以下是更改VTB的代码：
public static class VirtualToggleButton
{
#region attached properties
#region IsChecked
/// <summary>
/// IsChecked Attached Dependency Property
/// </summary>
public static readonly DependencyProperty IsCheckedProperty =
DependencyProperty.RegisterAttached("IsChecked", typeof(Nullable<bool>), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata((Nullable<bool>)false,
FrameworkPropertyMetadataOptions.BindsTwoWayByDefault | FrameworkPropertyMetadataOptions.Journal,
new PropertyChangedCallback(OnIsCheckedChanged)));
/// <summary>
/// Gets the IsChecked property. This dependency property
/// indicates whether the toggle button is checked.
/// </summary>
public static Nullable<bool> GetIsChecked(DependencyObject d)
{
return (Nullable<bool>)d.GetValue(IsCheckedProperty);
}
/// <summary>
/// Sets the IsChecked property. This dependency property
/// indicates whether the toggle button is checked.
/// </summary>
public static void SetIsChecked(DependencyObject d, Nullable<bool> value)
{
d.SetValue(IsCheckedProperty, value);
}
/// <summary>
/// Handles changes to the IsChecked property.
/// </summary>
private static void OnIsCheckedChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var pseudobutton = d as UIElement;
if (pseudobutton != null)
{
var newValue = (Nullable<bool>)e.NewValue;
if (newValue == true)
{
RaiseCheckedEvent(pseudobutton);
}
else if (newValue == false)
{
RaiseUncheckedEvent(pseudobutton);
}
else
{
RaiseIndeterminateEvent(pseudobutton);
}
}
}
#endregion
#region IsThreeState
/// <summary>
/// IsThreeState Attached Dependency Property
/// </summary>
public static readonly DependencyProperty IsThreeStateProperty =
DependencyProperty.RegisterAttached("IsThreeState", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata((bool)false));
/// <summary>
/// Gets the IsThreeState property. This dependency property
/// indicates whether the control supports two or three states.
/// IsChecked can be set to null as a third state when IsThreeState is true.
/// </summary>
public static bool GetIsThreeState(DependencyObject d)
{
return (bool)d.GetValue(IsThreeStateProperty);
}
/// <summary>
/// Sets the IsThreeState property. This dependency property
/// indicates whether the control supports two or three states.
/// IsChecked can be set to null as a third state when IsThreeState is true.
/// </summary>
public static void SetIsThreeState(DependencyObject d, bool value)
{
d.SetValue(IsThreeStateProperty, value);
}
#endregion
#region IsVirtualToggleButton
/// <summary>
/// IsVirtualToggleButton Attached Dependency Property
/// </summary>
public static readonly DependencyProperty IsVirtualToggleButtonProperty =
DependencyProperty.RegisterAttached("IsVirtualToggleButton", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata((bool)false,
new PropertyChangedCallback(OnIsVirtualToggleButtonChanged)));
/// <summary>
/// Gets the IsVirtualToggleButton property. This dependency property
/// indicates whether the object to which the property is attached is treated as a VirtualToggleButton.
/// If true, the object will respond to keyboard and mouse input the same way a ToggleButton would.
/// </summary>
public static bool GetIsVirtualToggleButton(DependencyObject d)
{
return (bool)d.GetValue(IsVirtualToggleButtonProperty);
}
/// <summary>
/// Sets the IsVirtualToggleButton property. This dependency property
/// indicates whether the object to which the property is attached is treated as a VirtualToggleButton.
/// If true, the object will respond to keyboard and mouse input the same way a ToggleButton would.
/// </summary>
public static void SetIsVirtualToggleButton(DependencyObject d, bool value)
{
d.SetValue(IsVirtualToggleButtonProperty, value);
}
/// <summary>
/// Handles changes to the IsVirtualToggleButton property.
/// </summary>
private static void OnIsVirtualToggleButtonChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var element = d as IInputElement;
if (element != null)
{
if ((bool)e.NewValue)
{
element.AddHandler(Mouse.PreviewMouseDownEvent, new MouseButtonEventHandler(OnPreviewMouseLeftButtonDown));
element.PreviewKeyDown += OnPreviewKeyDown;
}
else
{
element.RemoveHandler(Mouse.PreviewMouseDownEvent, new MouseButtonEventHandler(OnPreviewMouseLeftButtonDown));
element.PreviewKeyDown -= OnPreviewKeyDown;
}
}
}
#endregion
#region SuppressKeyboard
public static readonly DependencyProperty SuppressKeyboardProperty =
DependencyProperty.RegisterAttached("SuppressKeyboard", typeof (bool), typeof (VirtualToggleButton),
new FrameworkPropertyMetadata(false));
public static bool GetSuppressKeyboard(DependencyObject d)
{
return (bool)d.GetValue(SuppressKeyboardProperty);
}
public static void SetSuppressKeyboard(DependencyObject d, bool value)
{
d.SetValue(SuppressKeyboardProperty, value);
}
#endregion
#region SuppressMouse
public static readonly DependencyProperty SuppressMouseProperty =
DependencyProperty.RegisterAttached("SuppressMouse", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata(false));
public static bool GetSuppressMouse(DependencyObject d)
{
return (bool)d.GetValue(SuppressMouseProperty);
}
public static void SetSuppressMouse(DependencyObject d, bool value)
{
d.SetValue(SuppressKeyboardProperty, value);
}
#endregion
#endregion
#region routed events
#region Checked
/// <summary>
/// A static helper method to raise the Checked event on a target element.
/// </summary>
/// <param name="target">UIElement or ContentElement on which to raise the event</param>
internal static RoutedEventArgs RaiseCheckedEvent(UIElement target)
{
if (target == null)
return null;
var args = new RoutedEventArgs {RoutedEvent = ToggleButton.CheckedEvent};
RaiseEvent(target, args);
return args;
}
#endregion
#region Unchecked
/// <summary>
/// A static helper method to raise the Unchecked event on a target element.
/// </summary>
/// <param name="target">UIElement or ContentElement on which to raise the event</param>
internal static RoutedEventArgs RaiseUncheckedEvent(UIElement target)
{
if (target == null) return null;
RoutedEventArgs args = new RoutedEventArgs();
args.RoutedEvent = ToggleButton.UncheckedEvent;
RaiseEvent(target, args);
return args;
}
#endregion
#region Indeterminate
/// <summary>
/// A static helper method to raise the Indeterminate event on a target element.
/// </summary>
/// <param name="target">UIElement or ContentElement on which to raise the event</param>
internal static RoutedEventArgs RaiseIndeterminateEvent(UIElement target)
{
if (target == null) return null;
RoutedEventArgs args = new RoutedEventArgs();
args.RoutedEvent = ToggleButton.IndeterminateEvent;
RaiseEvent(target, args);
return args;
}
#endregion
#endregion
#region private methods
private static void OnPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
if (e.ChangedButton == MouseButton.Left && e.LeftButton == MouseButtonState.Pressed)
{
UpdateIsChecked(sender as DependencyObject);
var dob = sender as DependencyObject;
var suppress = dob != null && GetSuppressMouse(dob);
e.Handled = suppress;
}
}
private static void OnPreviewKeyDown(object sender, KeyEventArgs e)
{
var dob = sender as DependencyObject;
var suppress = dob != null && GetSuppressKeyboard(dob);
if (e.OriginalSource == sender)
{
if (e.Key == Key.Space)
{
// ignore alt+space which invokes the system menu
if ((Keyboard.Modifiers & ModifierKeys.Alt) == ModifierKeys.Alt)
return;
UpdateIsChecked(sender as DependencyObject);
e.Handled = suppress;
}
else if (e.Key == Key.Enter && (bool)(sender as DependencyObject).GetValue(KeyboardNavigation.AcceptsReturnProperty))
{
UpdateIsChecked(sender as DependencyObject);
e.Handled = suppress;
}
}
}
private static void UpdateIsChecked(DependencyObject d)
{
Nullable<bool> isChecked = GetIsChecked(d);
if (isChecked == true)
{
SetIsChecked(d, GetIsThreeState(d) ? (Nullable<bool>)null : (Nullable<bool>)false);
}
else
{
SetIsChecked(d, isChecked.HasValue);
}
}
private static void RaiseEvent(DependencyObject target, RoutedEventArgs args)
{
if (target is UIElement)
{
(target as UIElement).RaiseEvent(args);
}
else if (target is ContentElement)
{
(target as ContentElement).RaiseEvent(args);
}
}
#endregion
}
我也改变了一点点绑定：
<TreeView>
<TreeView.Resources>
<Style TargetType="TreeViewItem">
<Setter Property="IsExpanded" Value="True"/>
<Setter Property="cl:VirtualToggleButton.IsVirtualToggleButton" Value="True"/>
<Setter Property="cl:VirtualToggleButton.SuppressKeyboard" Value="True"/>
<!--<Setter Property="cl:VirtualToggleButton.SuppressMouse" Value="True"/>-->
</Style>
</TreeView.Resources>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Softwares}">
<TextBlock Text="{Binding Name}"/>
<HierarchicalDataTemplate.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox Focusable="False"
IsChecked="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type TreeViewItem}}
, Path=(cl:VirtualToggleButton.IsChecked), Mode=OneWay}"/>
<TextBlock Text="{Binding Name}" Height="Auto"/>
</StackPanel>
</DataTemplate>
</HierarchicalDataTemplate.ItemTemplate>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
这是非常奇怪的事情。 设置SuppressMouse并单击TreeViewItems时，它未被选中（这是一致行为），IsChecked设置为True，但CheckBox保持未选中状态。 我真的不知道为什么会这样，因为当使用键盘时一切都很好。 当SuppressMouse = False时，CheckBox会更改其状态，但是对于每个单击的TreeViewItem，都会调用两次OnPreviewMouseLeftButtonDown。这也很令人困惑。
问题：描述行为的原因是什么
答案 0 :(得分：0)
嗯，VirtualToggleButton的原始版本使用了MouseLeftButtonDown的冒泡事件。 我真正不喜欢的是点击控件将事件标记为已处理的机会。在给定的文章中就是这种情况，因为选择TreeViewItem不会引发mousedown事件处理程序。所以我决定使用隧道事件但是引入了忘记检查发件人和事件源的错误：root TreeViewItem将其状态设置为Checked而单击子项。
我添加了几个属性来控制是否允许事件通过元素树传播以及如何切换按钮（键盘或/和鼠标）。
VTB的最终版本：
public static class VirtualToggleButton
{
#region attached properties
#region IsChecked
public static readonly DependencyProperty IsCheckedProperty =
DependencyProperty.RegisterAttached("IsChecked", typeof(Nullable<bool>), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata((Nullable<bool>)false,
FrameworkPropertyMetadataOptions.BindsTwoWayByDefault | FrameworkPropertyMetadataOptions.Journal,
new PropertyChangedCallback(OnIsCheckedChanged)));
/// <summary>
/// Gets the IsChecked property. This dependency property
/// indicates whether the toggle button is checked.
/// </summary>
public static Nullable<bool> GetIsChecked(DependencyObject d)
{
return (Nullable<bool>)d.GetValue(IsCheckedProperty);
}
/// <summary>
/// Sets the IsChecked property. This dependency property
/// indicates whether the toggle button is checked.
/// </summary>
public static void SetIsChecked(DependencyObject d, Nullable<bool> value)
{
d.SetValue(IsCheckedProperty, value);
}
/// <summary>
/// Handles changes to the IsChecked property.
/// </summary>
private static void OnIsCheckedChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var pseudobutton = d as UIElement;
if (pseudobutton != null)
{
var newValue = (Nullable<bool>)e.NewValue;
if (newValue == true)
{
RaiseCheckedEvent(pseudobutton);
}
else if (newValue == false)
{
RaiseUncheckedEvent(pseudobutton);
}
else
{
RaiseIndeterminateEvent(pseudobutton);
}
}
}
#endregion
#region IsThreeState
/// <summary>
/// IsThreeState Attached Dependency Property
/// </summary>
public static readonly DependencyProperty IsThreeStateProperty =
DependencyProperty.RegisterAttached("IsThreeState", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata((bool)false));
/// <summary>
/// Gets the IsThreeState property. This dependency property
/// indicates whether the control supports two or three states.
/// IsChecked can be set to null as a third state when IsThreeState is true.
/// </summary>
public static bool GetIsThreeState(DependencyObject d)
{
return (bool)d.GetValue(IsThreeStateProperty);
}
/// <summary>
/// Sets the IsThreeState property. This dependency property
/// indicates whether the control supports two or three states.
/// IsChecked can be set to null as a third state when IsThreeState is true.
/// </summary>
public static void SetIsThreeState(DependencyObject d, bool value)
{
d.SetValue(IsThreeStateProperty, value);
}
#endregion
#region IsVirtualToggleButton
/// <summary>
/// IsVirtualToggleButton Attached Dependency Property
/// </summary>
public static readonly DependencyProperty IsVirtualToggleButtonProperty =
DependencyProperty.RegisterAttached("IsVirtualToggleButton", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata((bool)false,
new PropertyChangedCallback(OnIsVirtualToggleButtonChanged)));
/// <summary>
/// Gets the IsVirtualToggleButton property. This dependency property
/// indicates whether the object to which the property is attached is treated as a VirtualToggleButton.
/// If true, the object will respond to keyboard and mouse input the same way a ToggleButton would.
/// </summary>
public static bool GetIsVirtualToggleButton(DependencyObject d)
{
return (bool)d.GetValue(IsVirtualToggleButtonProperty);
}
/// <summary>
/// Sets the IsVirtualToggleButton property. This dependency property
/// indicates whether the object to which the property is attached is treated as a VirtualToggleButton.
/// If true, the object will respond to keyboard and mouse input the same way a ToggleButton would.
/// </summary>
public static void SetIsVirtualToggleButton(DependencyObject d, bool value)
{
d.SetValue(IsVirtualToggleButtonProperty, value);
}
/// <summary>
/// Handles changes to the IsVirtualToggleButton property.
/// </summary>
private static void OnIsVirtualToggleButtonChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var element = d as IInputElement;
if (element != null)
{
if ((bool)e.NewValue)
{
element.AddHandler(Mouse.PreviewMouseDownEvent, new MouseButtonEventHandler(OnPrevieMouseLeftButtonDown));
element.PreviewKeyDown += OnPreviewKeyDown;
}
else
{
element.RemoveHandler(Mouse.PreviewMouseDownEvent, new MouseButtonEventHandler(OnPrevieMouseLeftButtonDown));
element.PreviewKeyDown -= OnPreviewKeyDown;
}
}
}
#endregion
#region SuppressKeyboard
public static readonly DependencyProperty SuppressKeyboardProperty =
DependencyProperty.RegisterAttached("SuppressKeyboard", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata(false));
public static bool GetSuppressKeyboard(DependencyObject d)
{
return (bool)d.GetValue(SuppressKeyboardProperty);
}
public static void SetSuppressKeyboard(DependencyObject d, bool value)
{
d.SetValue(SuppressKeyboardProperty, value);
}
#endregion
#region SuppressMouse
public static readonly DependencyProperty SuppressMouseProperty =
DependencyProperty.RegisterAttached("SuppressMouse", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata(false));
public static bool GetSuppressMouse(DependencyObject d)
{
return (bool)d.GetValue(SuppressMouseProperty);
}
public static void SetSuppressMouse(DependencyObject d, bool value)
{
d.SetValue(SuppressKeyboardProperty, value);
}
#endregion
#region IsToggledByMouse
public static readonly DependencyProperty IsToggledByMouseProperty =
DependencyProperty.RegisterAttached("IsToggledByMouse", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata(true));
public static bool GetIsToggledByMouse(DependencyObject d)
{
return (bool)d.GetValue(IsToggledByMouseProperty);
}
public static void SetIsToggledByMouse(DependencyObject d, bool value)
{
d.SetValue(IsToggledByMouseProperty, value);
}
#endregion
#region IsToogledByKeyboard
public static readonly DependencyProperty IsToggledByKeyboardProperty =
DependencyProperty.RegisterAttached("IsToggledByKeyboard", typeof(bool), typeof(VirtualToggleButton),
new FrameworkPropertyMetadata(true));
public static bool GetIsToggledByKeyboard(DependencyObject d)
{
return (bool)d.GetValue(IsToggledByKeyboardProperty);
}
public static void SetIsToggledByKeyboard(DependencyObject d, bool value)
{
d.SetValue(IsToggledByKeyboardProperty, value);
}
#endregion
#endregion
#region routed events
#region Checked
internal static RoutedEventArgs RaiseCheckedEvent(UIElement target)
{
if (target == null)
return null;
var args = new RoutedEventArgs { RoutedEvent = ToggleButton.CheckedEvent };
RaiseEvent(target, args);
return args;
}
#endregion
#region Unchecked
/// <summary>
/// A static helper method to raise the Unchecked event on a target element.
/// </summary>
/// <param name="target">UIElement or ContentElement on which to raise the event</param>
internal static RoutedEventArgs RaiseUncheckedEvent(UIElement target)
{
if (target == null) return null;
RoutedEventArgs args = new RoutedEventArgs();
args.RoutedEvent = ToggleButton.UncheckedEvent;
RaiseEvent(target, args);
return args;
}
#endregion
#region Indeterminate
/// <summary>
/// A static helper method to raise the Indeterminate event on a target element.
/// </summary>
/// <param name="target">UIElement or ContentElement on which to raise the event</param>
internal static RoutedEventArgs RaiseIndeterminateEvent(UIElement target)
{
if (target == null) return null;
RoutedEventArgs args = new RoutedEventArgs();
args.RoutedEvent = ToggleButton.IndeterminateEvent;
RaiseEvent(target, args);
return args;
}
#endregion
#endregion
#region private methods
private static void OnPrevieMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
// Looking for the logically closest (up in elements tree) element
// Like a bubble in a tunneling event
var senderType = sender.GetType();
var depObj = e.OriginalSource as DependencyObject;
while (depObj != null && depObj.GetType() != senderType)
depObj = VisualTreeHelper.GetParent(depObj);
if (depObj != sender)
return;
if (e.ChangedButton == MouseButton.Left && e.LeftButton == MouseButtonState.Pressed)
{
var dob = sender as DependencyObject;
var suppress = dob != null && GetSuppressMouse(dob);
e.Handled = suppress;
if (!GetIsToggledByMouse(depObj))
return;
UpdateIsChecked(sender as DependencyObject);
}
}
private static void OnPreviewKeyDown(object sender, KeyEventArgs e)
{
if (e.Key != Key.Space && e.Key != Key.Enter )
return;
var senderType = sender.GetType();
var p = e.OriginalSource as DependencyObject;
while (p != null && p.GetType() != senderType)
p = VisualTreeHelper.GetParent(p);
if (p != sender)
return;
var dob = sender as DependencyObject;
var suppress = dob != null && GetSuppressKeyboard(dob);
if (e.Key == Key.Space)
{
// ignore alt+space which invokes the system menu
if ((Keyboard.Modifiers & ModifierKeys.Alt) == ModifierKeys.Alt)
return;
UpdateIsChecked(sender as DependencyObject);
e.Handled = suppress;
}
else if (e.Key == Key.Enter && (bool)(sender as DependencyObject).GetValue(KeyboardNavigation.AcceptsReturnProperty))
{
UpdateIsChecked(sender as DependencyObject);
e.Handled = suppress;
}
}
private static void UpdateIsChecked(DependencyObject d)
{
Nullable<bool> isChecked = GetIsChecked(d);
if (isChecked == true)
{
SetIsChecked(d, GetIsThreeState(d) ? (Nullable<bool>)null : (Nullable<bool>)false);
}
else
{
SetIsChecked(d, isChecked.HasValue);
}
}
private static void RaiseEvent(DependencyObject target, RoutedEventArgs args)
{
if (target is UIElement)
{
(target as UIElement).RaiseEvent(args);
}
else if (target is ContentElement)
{
(target as ContentElement).RaiseEvent(args);
}
}
#endregion
}