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我有一个覆盖 OnApplyTemplate 的自定义控件。在其中，我尝试访问子模板的子模板，但它们似乎没有被加载。我希望：当点击 a 的内部时，不会PART_IncreaseButton关闭，只是让点击对点击做出反应。Popupxtk:SplitButtonPopupButton

CustomIntegerUpDown并且CustomSplitButton源自 Xceed Extended WPF Toolkit。CustomIntegerUpDown 没有改变样式或模板或代码隐藏，目前它的唯一目的是做我上面所说的，但我只是在它的开始。以下是所有相关来源。

我试过这个：

IncrementButton = Utils.FindChild<RepeatButton>(PartPopup, "PART_IncreaseButton")

之后 IncrementButton 为空，尽管在即时窗口中：

Utils.FindChild<Popup>(this, "PART_Popup")返回从Popup获得的GetTemplateChild("PART_Popup")。

然后

Utils.FindChild<ButtonSpinner>(PartPopup, "PART_Spinner")返回null。

Utils.FindChild<CustomIntegerUpDown>(PartPopup, "MyCustomIntegerUpDown")返回null。

VisualTreeHelper.GetChildrenCount(PartPopup)返回0。

PartPopup.ApplyTemplate()返回false。

我也看到了这个，我不确定是否值得尝试这种方式。

FindChild这是（取自这里）：

/// <summary>
/// Finds a Child of a given item in the visual tree.
/// </summary>
/// <param name="parent">A direct parent of the queried item.</param>
/// <typeparam name="T">The type of the queried item.</typeparam>
/// <param name="childName">x:Name or Name of child. </param>
/// <returns>The first parent item that matches the submitted type parameter.
/// If not matching item can be found,
/// a null parent is being returned.</returns>
public static T FindChild<T>(System.Windows.DependencyObject parent, string childName)
    where T : System.Windows.DependencyObject
{
    // Confirm parent and childName are valid.
    if (parent == null) return null;
    T foundChild = null;
    int childrenCount = System.Windows.Media.VisualTreeHelper.GetChildrenCount(parent);
    for (int i = 0; i < childrenCount; i++)
    {
        var child = System.Windows.Media.VisualTreeHelper.GetChild(parent, i);
        // If the child is not of the request child type child
        T childType = child as T;
        if (childType == null)
        {
            // recursively drill down the tree
            foundChild = FindChild<T>(child, childName);
            // If the child is found, break so we do not overwrite the found child.
            if (foundChild != null) break;
        }
        else if (!string.IsNullOrEmpty(childName))
        {
            var frameworkElement = child as System.Windows.FrameworkElement;
            // If the child's name is set for search
            if (frameworkElement != null && frameworkElement.Name == childName)
            {
                // if the child's name is of the request name
                foundChild = (T)child;
                break;
            }
        }
        else
        {
            // child element found.
            foundChild = (T)child;
            break;
        }
    }
    return foundChild;
}

在CustomSplitButton.xaml.cs我有这个：

internal Popup PartPopup;
internal Button PartButtonWith1, PartButtonWith5, PartButtonWith10, PartButtonWithCustom;
internal RepeatButton IncrementButton;
public override void OnApplyTemplate()
{
    base.OnApplyTemplate();
    PartPopup = (Popup)GetTemplateChild("PART_Popup");
    PartButtonWith1 = (Button)GetTemplateChild("PART_ButtonWith1");
    PartButtonWith5 = (Button)GetTemplateChild("PART_ButtonWith5");
    PartButtonWith10 = (Button)GetTemplateChild("PART_ButtonWith10");
    PartButtonWithCustom = (Button)GetTemplateChild("PART_ButtonWithCustom");
    PartPopup.ApplyTemplate();
    IncrementButton = Utils.FindChild<RepeatButton>(PartPopup, "PART_IncreaseButton");
    if (PartPopup != null)
    {
        PartPopup.PreviewMouseDown += PART_Popup_PreviewMouseUp;
        PartPopup.PreviewMouseUp += PART_Popup_PreviewMouseUp;
    }
    if (PartButtonWith1 != null)
    {
        PartButtonWith1.Click += Btns_NewTimer_Click;
    }
    if (PartButtonWith5 != null)
    {
        PartButtonWith5.Click += Btns_NewTimer_Click;
    }
    if (PartButtonWith10 != null)
    {
        PartButtonWith10.Click += Btns_NewTimer_Click;
    }
    if (PartButtonWithCustom != null)
    {
        PartButtonWithCustom.Click += BtnCustom_Click;
    }
}

可视化树是这样的：

带有实时视觉树的屏幕截图

CustomSplitButton的样式如下（xmlns:xtkThemes="clr-namespace:Xceed.Wpf.Toolkit.Themes;assembly=Xceed.Wpf.Toolkit"）：

<Style x:Key="AddCountSplitButtonStyle" TargetType="{x:Type xtk:SplitButton}">
    <Setter Property="BorderThickness" Value="1"/>
    <Setter Property="IsTabStop" Value="False"/>
    <Setter Property="HorizontalContentAlignment" Value="Center"/>
    <Setter Property="VerticalContentAlignment" Value="Center"/>
    <Setter Property="Background" Value="{DynamicResource {ComponentResourceKey ResourceId=ButtonNormalBackgroundKey, TypeInTargetAssembly={x:Type xtkThemes:ResourceKeys}}}"/>
    <Setter Property="BorderBrush" Value="{DynamicResource {ComponentResourceKey ResourceId=ButtonNormalOuterBorderKey, TypeInTargetAssembly={x:Type xtkThemes:ResourceKeys}}}"/>
    <Setter Property="DropDownContentBackground">
        <Setter.Value>
            <LinearGradientBrush EndPoint="0,1" StartPoint="0,0">
                <GradientStop Color="#FFF0F0F0" Offset="0"/>
                <GradientStop Color="#FFE5E5E5" Offset="1"/>
            </LinearGradientBrush>
        </Setter.Value>
    </Setter>
    <Setter Property="Padding" Value="3"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type xtk:SplitButton}">
                <Grid x:Name="MainGrid" SnapsToDevicePixels="True">
                    <xtk:ButtonChrome x:Name="ControlChrome" BorderThickness="0" Background="{TemplateBinding Background}" RenderEnabled="{TemplateBinding IsEnabled}">
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*"/>
                                <ColumnDefinition Width="Auto"/>
                            </Grid.ColumnDefinitions>
                            <Button x:Name="PART_ActionButton" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="0" Padding="{TemplateBinding Padding}" Style="{x:Null}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}">
                                <Button.Template>
                                    <ControlTemplate TargetType="{x:Type Button}">
                                        <ContentPresenter ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" ContentStringFormat="{TemplateBinding ContentStringFormat}"/>
                                    </ControlTemplate>
                                </Button.Template>
                                <Grid>
                                    <xtk:ButtonChrome x:Name="ActionButtonChrome" BorderBrush="{TemplateBinding BorderBrush}" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" RenderMouseOver="{Binding IsMouseOver, ElementName=PART_ActionButton}" RenderPressed="{Binding IsPressed, ElementName=PART_ActionButton}" RenderEnabled="{TemplateBinding IsEnabled}">
                                        <xtk:ButtonChrome.BorderThickness>
                                            <Binding ConverterParameter="2" Path="BorderThickness" RelativeSource="{RelativeSource TemplatedParent}">
                                                <Binding.Converter>
                                                    <xtk:ThicknessSideRemovalConverter/>
                                                </Binding.Converter>
                                            </Binding>
                                        </xtk:ButtonChrome.BorderThickness>
                                        <ContentPresenter x:Name="ActionButtonContent" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                                    </xtk:ButtonChrome>
                                </Grid>
                            </Button>
                            <ToggleButton x:Name="PART_ToggleButton" Grid.Column="1" IsChecked="{Binding IsOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}">
                                <ToggleButton.IsHitTestVisible>
                                    <Binding Path="IsOpen" RelativeSource="{RelativeSource TemplatedParent}">
                                        <Binding.Converter>
                                            <xtk:InverseBoolConverter/>
                                        </Binding.Converter>
                                    </Binding>
                                </ToggleButton.IsHitTestVisible>
                                <ToggleButton.Template>
                                    <ControlTemplate TargetType="{x:Type ToggleButton}">
                                        <ContentPresenter ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" ContentStringFormat="{TemplateBinding ContentStringFormat}"/>
                                    </ControlTemplate>
                                </ToggleButton.Template>
                                <Grid>
                                    <xtk:ButtonChrome x:Name="ToggleButtonChrome" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="1,0" RenderMouseOver="{Binding IsMouseOver, ElementName=PART_ToggleButton}" RenderPressed="{Binding IsPressed, ElementName=PART_ToggleButton}" RenderChecked="{TemplateBinding IsOpen}" RenderEnabled="{TemplateBinding IsEnabled}">
                                        <Grid x:Name="arrowGlyph" IsHitTestVisible="False" Margin="4,3">
                                            <Path x:Name="Arrow" Data="M0,0L3,0 4.5,1.5 6,0 9,0 4.5,4.5z" Fill="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" Height="5" Margin="0,1,0,0" Width="9"/>
                                        </Grid>
                                    </xtk:ButtonChrome>
                                </Grid>
                            </ToggleButton>
                        </Grid>
                    </xtk:ButtonChrome>
                    <Popup x:Name="PART_Popup" AllowsTransparency="True" Focusable="False" HorizontalOffset="1" IsOpen="{Binding IsChecked, ElementName=PART_ToggleButton}" Placement="{TemplateBinding DropDownPosition}" VerticalOffset="1"
                                StaysOpen="False">

                        <Border BorderThickness="{DynamicResource DefaultBorderThickness}" Margin="10,0,10,10" Background="{DynamicResource DarkerBaseBrush}" BorderBrush="{DynamicResource PopupBorderBrush}" CornerRadius="{DynamicResource DefaultCornerRadius}">
                            <Grid MinWidth="100" Name="PART_ContentPresenter">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto"/>
                                    <RowDefinition Height="Auto"/>
                                    <RowDefinition Height="Auto"/>
                                    <RowDefinition Height="Auto"/>
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="*"/>
                                    <ColumnDefinition Width="Auto"/>
                                </Grid.ColumnDefinitions>
                                <Button x:Name="PART_ButtonWith1" Grid.Row="0" Grid.ColumnSpan="2">
                                    1
                                </Button>
                                <Button x:Name="PART_ButtonWith5" Grid.Row="1" Grid.ColumnSpan="2">
                                    5
                                </Button>
                                <Button x:Name="PART_ButtonWith10" Grid.Row="2" Grid.ColumnSpan="2">
                                    10
                                </Button>
                                <local:CustomIntegerUpDown Grid.Row="3" Value="1"
                                                            Increment="1" ClipValueToMinMax="True"              
                                                            x:Name="MyCustomIntegerUpDown">
                                </local:CustomIntegerUpDown>
                                <Button x:Name="PART_ButtonWithCustom" Grid.Row="3" Grid.Column="1" Padding="2,2,2,2">
                                    &gt;
                                </Button>
                            </Grid>
                            <Border.Effect>
                                <DropShadowEffect ShadowDepth="0" BlurRadius="10" Color="{DynamicResource Base6Color}" />
                            </Border.Effect>
                        </Border>
                    </Popup>
                </Grid>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsEnabled" Value="False">
                        <Setter Property="Fill" TargetName="Arrow" Value="#FFAFAFAF"/>
                        <Setter Property="Foreground" TargetName="ActionButtonChrome" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

在OnApplyTemplate我希望能够在this. 但我没有找到办法做到这一点。

我的相关问题在这里。

更新 1

示例的起点已更新（它使用TryFindVisualChildElementByNameBionicCode 答案中的扩展方法）：

internal Popup PartPopup;
internal Button PartButtonWith1, PartButtonWith5, PartButtonWith10, PartButtonWithCustom;
internal RepeatButton IncrementButton;

private void SplitButton_Loaded(object sender, RoutedEventArgs e)
{
    PartPopup = (Popup)GetTemplateChild("PART_Popup");
    PartButtonWith1 = (Button)GetTemplateChild("PART_ButtonWith1");
    PartButtonWith5 = (Button)GetTemplateChild("PART_ButtonWith5");
    PartButtonWith10 = (Button)GetTemplateChild("PART_ButtonWith10");
    PartButtonWithCustom = (Button)GetTemplateChild("PART_ButtonWithCustom");

    if (PartPopup != null)
    {
        PartPopup.ApplyTemplateRecursively();

        if (PartPopup.TryFindVisualChildElementByName("PART_IncreaseButton", out FrameworkElement incButton))
        {
            IncrementButton = (RepeatButton)incButton;

            // do something with IncrementButton here
        }

        PartPopup.PreviewMouseDown += PART_Popup_PreviewMouseUp;
        PartPopup.PreviewMouseUp += PART_Popup_PreviewMouseUp;
    }

    if (PartButtonWith1 != null)
    {
        PartButtonWith1.Click += Btns_NewTimer_Click;
    }
    if (PartButtonWith5 != null)
    {
        PartButtonWith5.Click += Btns_NewTimer_Click;
    }
    if (PartButtonWith10 != null)
    {
        PartButtonWith10.Click += Btns_NewTimer_Click;
    }
    if (PartButtonWithCustom != null)
    {
        PartButtonWithCustom.Click += BtnCustom_Click;
    }
}

上面使用的ApplyTemplateRecursively扩展方法，有2个版本：

不工作版本

是否有可能使这个版本以某种方式工作？我认为它更有效率。

/// <summary>
/// Not working because the ApplyTemplate affects the VisualTree and when applying
/// templates recursively it does not see the correct updated visual tree to be able
/// to continue.
/// </summary>
/// <param name="root"></param>
internal static void ApplyTemplateRecursively(this System.Windows.DependencyObject root)
{
    if (root is System.Windows.Controls.Primitives.Popup p)
    {
        p.Child.ApplyTemplateRecursively();
        return;
    }

    if (root is FrameworkElement r)
    {
        r.ApplyTemplate();
    }

    foreach (object element in System.Windows.LogicalTreeHelper.GetChildren(root))
    {
        if (element is System.Windows.DependencyObject el)
        {
            ApplyTemplateRecursively(el);
        }
    }
}

工作版本

/// <summary>
/// I am not sure if this is sufficiently efficient, because it goes through the entire visual tree.
/// </summary>
/// <param name="root"></param>
internal static void ApplyTemplateRecursively(this System.Windows.DependencyObject root)
{
    if (root is System.Windows.Controls.Primitives.Popup p)
    {
        p.Child.ApplyTemplateRecursively();
        return;
    }

    if (root is FrameworkElement r)
    {
        r.ApplyTemplate();
    }

    for (int i = 0; i < System.Windows.Media.VisualTreeHelper.GetChildrenCount(root); ++i)
    {
        DependencyObject d = VisualTreeHelper.GetChild(root, i);
        ApplyTemplateRecursively(d);
    }
}

现在我正在尝试解决实际问题。

更新 2

我已经报告了这个问题。

4

1 回答 1

2

The point is that the content of a Popup is not directly part of the visual tree. That's why looking for visual children of a Popup will always return null. The content of a Popup is rendered separately and is assigned to the Popup.Child property. You need to extract those from the Child property before continuing tree traversal inside the Popup.

The following is a custom visual tree helper method to return the first child element that matches a given name. This helper properly searches inside a Popup element. This method is an Extension Method of type DependencyObject and has to be put into a static class:

public static bool TryFindVisualChildElementByName(
  this DependencyObject parent,
  string childElementName,
  out FrameworkElement resultElement)
{
  resultElement = null;

  if (parent is Popup popup)
  {
    parent = popup.Child;
    if (parent == null)
    {
      return false;
    }
  }

  for (var childIndex = 0; childIndex < VisualTreeHelper.GetChildrenCount(parent); childIndex++)
  {
    DependencyObject childElement = VisualTreeHelper.GetChild(parent, childIndex);        

    if (childElement is FrameworkElement uiElement && uiElement.Name.Equals(
          childElementName,
          StringComparison.OrdinalIgnoreCase))
    {
      resultElement = uiElement;
      return true;
    }

    if (childElement.TryFindVisualChildElementByName(childElementName, out resultElement))
    {
      return true;
    }
  }

  return false;
}

It's an Extension Method and it is used like this:

CustomSplitButton.xaml.cs 

// Constructor
public CustomSplitButton()
{
  this.Loaded += GetParts;
}

private void GetParts(object sender, RoutedEventArgs e)
{
  if (this.TryFindVisualChildElementByName("PART_Popup", out FrameworkElement popupPart))
  {
    if (popupPart.TryFindVisualChildElementByName("PART_ContentPresenter", out FrameworkElement contentPresenter))
    {
      if (!contentPresenter.IsLoaded)
      {
        contentPresenter.Loaded += CompleteSearch;
      }
      else 
      {
        CompleteSearch(contentPresenter, null);
      }
    }
  }
}

private void CompleteSearch(object sender, RoutedEventArgs e)
{      
  contentPresenter.Loaded -= CompleteSearch;

  if ((sender as DependencyObject).TryFindVisualChildElementByName("PART_IncreaseButton", out FrameworkElement increaseButton))
  {        
    IncrementButton = (RepeatButton) increaseButton;
  }
}

Remarks

It is very important to search after a parent element was Loaded.

This is true for all elements in the visual tree. Since the SplitButton consists of a drop down that is collapsed by default, not all contents are loaded initially. Once the drop down is opened the SplitButton makes its content visible, which will add them to the visual tree. Up to this point the SplitButton.IsLoaded property will return false, indicating the button's incomplete visual state. What you need to do is, once you encountered a FrameworkElement where FrameworkElement.IsLoaded returns false you have to subscribe to the FrameworkElement.Loaded event. In this handler you can continue the visual tree traversal.
Popup like elements or collapsed controls add complexity to the visual tree traversal.

Edit: Keep Popup open when content was clicked

Now that you have told me that you are using the SplitButton inside a ToolBar I instantly knew the origin of your problem:

Classes in WPF which are focus scopes by default are Window, MenuItem, ToolBar, and ContextMenu. [Microsoft Docs: Logical Focus]

Simply remove the focus scope from the ToolBar to prevent the focus from being removed from the Popup as soon as any of its content was clicked (received logical focus):

<ToolBar FocusManager.IsFocusScope="False"> 
  <CustomSplitButton />
</ToolBar>

Edit: Keep Popup open when clicked on PART_ToggleButton while the Popup is open

To prevent the Popup from closing and reopening when the PART_ToggleButton is clicked while the Popup is open you need to handle the mouse down event (application wide) and the opening of the Popup yourself.

First modify the PART_Popup to make it stay open and remove the binding from the IsOpen property:

CustomSplitButton.xaml

<Popup x:Name="PART_Popup"
       IsOpen="False"
       StaysOpen="True"
       AllowsTransparency="True"
       Focusable="False"
       HorizontalOffset="1"
       Placement="{TemplateBinding DropDownPosition}"
       VerticalOffset="1">

Then in your CustomSplitButton observe the mouse device for mouse down events and determine the hit target. I assume that you retrieved the underlying PART_Popup and PART_ToggleButton element and stored it in a property named PartPopup and PartToggleButton (see first part of this answer on how to do it):

CustomSplitButton.xaml.cs

public CustomSplitButton()
{
  this.Loaded += OnLoaded;
}

private void OnLoaded(object sender, RoutedEventArgs e)
{
  Mouse.AddPreviewMouseDownHandler(Application.Current.MainWindow, KeepPopupOpen);
}

private void KeepPopupOpen(object sender, RoutedEventArgs routedEventArgs)
{
  var mouseClickSourceElement = routedEventArgs.OriginalSource as DependencyObject;
  var isPopupContentClicked = false;
  var isPartToggleButtonClicked = 
    object.ReferenceEquals(routedEventArgs.Source, this) 
      && mouseClickSourceElement.TryFindVisualParentElement(out ButtonBase button) 
      && button.Name.Equals(this.PartToggleButton.Name, StringComparison.OrdinalIgnoreCase);

  if (!isPartToggleButtonClicked)
  {
    isPopupContentClicked = 
      object.ReferenceEquals(routedEventArgs.Source, this) 
        && mouseClickSourceElement.TryFindVisualParentElementByName("PART_ContentPresenter", out FrameworkElement popupContentPresenter));
  }

  this.PartPopup.IsOpen = this.IsOpen = isPartToggleButtonClicked || isPopupContentClicked ;
}

Extension Methods to find the visual parent by type and by name

public static class HelperExtensions
{
  public static bool TryFindVisualParentElement<TParent>(this DependencyObject child, out TParent resultElement)
    where TParent : DependencyObject
  {
    resultElement = null;

    if (child == null)
    {
      return false;
    }

    DependencyObject parentElement = VisualTreeHelper.GetParent(child);

    if (parentElement is TParent parent)
    {
      resultElement = parent;
      return true;
    }

    return parentElement.TryFindVisualParentElement(out resultElement);
  }

  public static bool TryFindVisualParentElementByName(
      this DependencyObject child,
      string elementName,
      out FrameworkElement resultElement)
    {
      resultElement = null;

      if (child == null)
      {
        return false;
      }

      DependencyObject parentElement = VisualTreeHelper.GetParent(child);

      if (parentElement is FrameworkElement frameworkElement &&
          frameworkElement.Name.Equals(elementName, StringComparison.OrdinalIgnoreCase))
      {
        resultElement = frameworkElement;
        return true;
      }

      return parentElement.TryFindVisualParentElementByName(elementName, out resultElement);
    }
  }
}
于 2019-09-08T18:47:03.753 回答