[WPF 自定义控件]创建包含CheckBox的ListBoxItem

02/17 09:36
阅读数 32

1. 前言

Xceed wpftoolkit提供了一个CheckListBox,效果如下:

不过它用起来不怎么样,与其这样还不如参考UWP的ListView实现,而且动画效果也很好看:

它的样式如下:

<ListViewItemPresenter ContentTransitions="{TemplateBinding ContentTransitions}"
    x:Name="Root"
    Control.IsTemplateFocusTarget="True"
    FocusVisualMargin="{TemplateBinding FocusVisualMargin}"
    SelectionCheckMarkVisualEnabled="{ThemeResource ListViewItemSelectionCheckMarkVisualEnabled}"
    CheckBrush="{ThemeResource ListViewItemCheckBrush}"
    CheckBoxBrush="{ThemeResource ListViewItemCheckBoxBrush}"
    DragBackground="{ThemeResource ListViewItemDragBackground}"
    DragForeground="{ThemeResource ListViewItemDragForeground}"
    FocusBorderBrush="{ThemeResource ListViewItemFocusBorderBrush}"
    FocusSecondaryBorderBrush="{ThemeResource ListViewItemFocusSecondaryBorderBrush}"
    PlaceholderBackground="{ThemeResource ListViewItemPlaceholderBackground}"
    PointerOverBackground="{ThemeResource ListViewItemBackgroundPointerOver}"
    PointerOverForeground="{ThemeResource ListViewItemForegroundPointerOver}"
    SelectedBackground="{ThemeResource ListViewItemBackgroundSelected}"
    SelectedForeground="{ThemeResource ListViewItemForegroundSelected}"
    SelectedPointerOverBackground="{ThemeResource ListViewItemBackgroundSelectedPointerOver}"
    PressedBackground="{ThemeResource ListViewItemBackgroundPressed}"
    SelectedPressedBackground="{ThemeResource ListViewItemBackgroundSelectedPressed}"
    DisabledOpacity="{ThemeResource ListViewItemDisabledThemeOpacity}"
    DragOpacity="{ThemeResource ListViewItemDragThemeOpacity}"
    ReorderHintOffset="{ThemeResource ListViewItemReorderHintThemeOffset}"
    HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
    VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
    ContentMargin="{TemplateBinding Padding}"
    CheckMode="{ThemeResource ListViewItemCheckMode}"
    RevealBackground="{ThemeResource ListViewItemRevealBackground}"
    RevealBorderThickness="{ThemeResource ListViewItemRevealBorderThemeThickness}"
    RevealBorderBrush="{ThemeResource ListViewItemRevealBorderBrush}">

属性是很多了,但这里没有自定义CheckBox样式的方法,而且也没法参考它的动画如何实现。幸好UWP还提供了一个ListViewItemExpanded样式,里面有完整的布局、VisualState等,不过总共有差不多500行,只拿其中MultiSelectStates的部分也将近100行,这太过复杂了,这还是有些麻烦,在WPF中实现起来反而简单很多。

2. 实现

微软的文档中有介绍如何Create ListViewItems with a CheckBox,原理十分简单:

<DataTemplate x:Key="FirstCell">
  <StackPanel Orientation="Horizontal">
    <CheckBox IsChecked="{Binding Path=IsSelected, 
      RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListViewItem}}}"/>
  </StackPanel>
</DataTemplate>

就是在控件模板中添加一个CheckBox并且这个CheckBox通过FindAncestor的Binding方式绑定到ListViewItem的IsSelected属性。虽然是ListView的方法,但它同样适用于ListBox。所以我使用这个方式封装了一个ListBox控件,目前基本上没什么功能,就只是在每个ListBoxItem前面加上一个CheckBox。以前介绍过如何自定义ItemsControl,要自定义一个ListBox控件,同样需要三部:

  1. 定义ListBox
  2. 关联ListBoxItem和ListBox
  3. 实现ListBox的逻辑
public class ExtendedListBox : ListBox
{
    public static readonly DependencyProperty IsMultiSelectCheckBoxEnabledProperty =
        DependencyProperty.Register(nameof(IsMultiSelectCheckBoxEnabled), typeof(bool), typeof(ExtendedListBox), new PropertyMetadata(true));

    public bool IsMultiSelectCheckBoxEnabled
    {
        get { return (bool)GetValue(IsMultiSelectCheckBoxEnabledProperty); }
        set { SetValue(IsMultiSelectCheckBoxEnabledProperty, value); }
    }

    protected override DependencyObject GetContainerForItemOverride()
    {
        return new ExtendedListBoxItem();
    }
}


public class ExtendedListBoxItem : ListBoxItem
{
    public ExtendedListBoxItem()
    {
        DefaultStyleKey = typeof(ExtendedListBoxItem);
    }
}

上面就是全部代码。定义了ExtendedListBoxExtendedListBoxItem两个类,然后重写GetContainerForItemOverride关联这两个类,最后在ExtendedListBox的代码里模仿UWP的ListView提供了IsMultiSelectCheckBoxEnabled属性,其他功能主要由XAML提供:

<Grid.ColumnDefinitions>
    <ColumnDefinition Width="Auto"/>
    <ColumnDefinition/>
</Grid.ColumnDefinitions>
<Primitives:KinoResizer>
    <CheckBox Margin="{TemplateBinding Padding}"
              IsChecked="{Binding IsSelected, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
              VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
              IsTabStop="False"
              x:Name="SelectionCheckMark"/>
</Primitives:KinoResizer>
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" Grid.Column="1"
                  Margin="{TemplateBinding Padding}"/>

ControlTemplate使用Resizer包装CheckBox,这是为了CheckBox隐藏或显示时有过渡动画。然后在ControlTemplate.Triggers里添加两个DataTrigger,根据所属的ListBox的IsMultiSelectCheckBoxEnabledSelectionMode显示或隐藏SelectionCheckMark:

<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ListBox},Path=SelectionMode}"
             Value="Single">
    <Setter Property="Visibility"
            TargetName="SelectionCheckMark"
            Value="Collapsed" />
</DataTrigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ListBox},Path=IsMultiSelectCheckBoxEnabled}"
             Value="False">
    <Setter Property="Visibility"
            TargetName="SelectionCheckMark"
            Value="Collapsed" />
</DataTrigger>

最终效果如下:

3. 添加VisualState

WPF的Button的ControlTemplate没有使用VisualState,但Button支持VisualState,用户可以自定义使用VisualState的ControlTemplate。ExtendedListBoxItem也模仿UWP提供了MultiSelectEnabled和MultiSelectDisabled两个VisualState,因为ListBoxItem需要知道承载它的ListBox的IsMultiSelectCheckBoxEnabled和SelectionMode,所以需要给ListBoxItem添加一个Owner属性,并重载ListBox的PrepareContainerForItemOverride函数,在这个函数中为ListBoxItem的Owner赋值:

protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
{
    base.PrepareContainerForItemOverride(element, item);
    if (element is ExtendedListBoxItem listBoxItem)
        listBoxItem.Owner = this;
}

ListBoxItem中使用监视Owner的IsMultiSelectCheckBoxEnabled和SelectionMode的改变,并在这两个值改变时更新VisualState:

protected virtual void OnOwnerChanged(ExtendedListBox oldValue, ExtendedListBox newValue)
{
    if (oldValue != null)
    {
        var descriptor = DependencyPropertyDescriptor.FromProperty(ListBox.SelectionModeProperty, typeof(ExtendedListBox));
        descriptor.RemoveValueChanged(newValue, OnSelectionModeChanged);

        descriptor = DependencyPropertyDescriptor.FromProperty(ExtendedListBox.IsMultiSelectCheckBoxEnabledProperty, typeof(ExtendedListBox));
        descriptor.RemoveValueChanged(newValue, OnIsMultiSelectCheckBoxEnabledChanged);
    }
    if (newValue != null)
    {
        var descriptor = DependencyPropertyDescriptor.FromProperty(ListBox.SelectionModeProperty, typeof(ExtendedListBox));
        descriptor.AddValueChanged(newValue, OnSelectionModeChanged);

        descriptor = DependencyPropertyDescriptor.FromProperty(ExtendedListBox.IsMultiSelectCheckBoxEnabledProperty, typeof(ExtendedListBox));
        descriptor.AddValueChanged(newValue, OnIsMultiSelectCheckBoxEnabledChanged);
    }
}

private void OnSelectionModeChanged(object sender, EventArgs args)
{
    UpdateVisualStates(true);
}

private void OnIsMultiSelectCheckBoxEnabledChanged(object sender, EventArgs args)
{
    UpdateVisualStates(true);
}

为了使用VisualState我在ControlTemplate多写了80行代码,因为没有用上VisualTransition所以这个ControlTemplate有一些Bug,反正只是用来验证添加的两个VisualState是否有效。在ListBoxItem里用Trigger比使用VisualState更简洁有效。

4. 使用同样的原理为DataGrid的行添加ChechBox

DataGrid也可以用同样的原理为每一行添加CheckBox,只不过DataGrid的Template会负责很多。

首先自定义一个DataGrid类:

public class ExtendedDataGrid : DataGrid, IMultiSelector
{
    // Using a DependencyProperty as the backing store for IsMultiSelectCheckBoxEnabled.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty IsMultiSelectCheckBoxEnabledProperty =
        DependencyProperty.Register(nameof(IsMultiSelectCheckBoxEnabled), typeof(bool), typeof(ExtendedDataGrid), new PropertyMetadata(true));

    public ExtendedDataGrid()
    {
        DefaultStyleKey = typeof(ExtendedDataGrid);
    }

    public bool IsMultiSelectCheckBoxEnabled
    {
        get { return (bool)GetValue(IsMultiSelectCheckBoxEnabledProperty); }
        set { SetValue(IsMultiSelectCheckBoxEnabledProperty, value); }
    }
}

然后定义一个RowHeaderTemplate

<DataTemplate x:Key="DataGridRowHeaderTemplate">
    <Grid>
        <CheckBox IsChecked="{Binding IsSelected, Mode=TwoWay, RelativeSource={RelativeSource AncestorType={x:Type DataGridRow}, Mode=FindAncestor}}"
                      x:Name="SelectionCheckBox"/>
    </Grid>
</DataTemplate>

在DataGrid的Style上应用这个RowHeaderTemplate。最后再DataGrid的Style的Triggers中添加两个DataTrigger:

<Trigger Property="SelectionMode" Value="Single">
    <Setter Property="HeadersVisibility"  Value="Column" />
</Trigger>
<Trigger Property="IsMultiSelectCheckBoxEnabled" Value="False">
    <Setter Property="HeadersVisibility"  Value="Column"/>
</Trigger>

HeadersVisibility是个DataGridHeadersVisibility的属性,它用于控制DataGrid行和列的Header是否显示,因为我在每一行的开头放了CheckBox(就是使用上面定义的RowHeaderTempalte),所以定一只只显示Column的Header的话相当于隐藏了这个CheckBox,运行效果如下:

5. 结语

ListBox和DataGrid的自定义是个很大的话题,这里只实现最简单的功能,通常会根据业务需求逐渐增加更多需求。如果有更复杂的需求,我建议买商业的控件,毕竟DataGrid的自定义可以很复杂,花时间不如花钱。

6. 参考

How to_ Create ListViewItems with a CheckBox - WPF _ Microsoft Docs

ListBox Class (System.Windows.Controls) _ Microsoft Docs

DataGrid Class (System.Windows.Controls) _ Microsoft Docs

7. 源码

Kino.Toolkit.Wpf_ExtendedListBox.cs at master

Kino.Toolkit.Wpf_ExtendedDataGrid.cs at master

原文出处:https://www.cnblogs.com/dino623/p/Create_ListBoxIte_with_a_CheckBox.html

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