VisualStateManager.GoToState在ChildWindow中的DataGrid上不起作用

Question

我扩展了System.Windows.Controls.DataGrid控件，以便在ItemsSource为null或为空时添加静态的空集合消息。 决定是否显示消息的逻辑是使用可视状态完成的，如下所示。 此逻辑在页面或用户控件中完美运行，但是当直接在ChildWindow上使用扩展的DataGrid时，即使逻辑被正确触发，该消息也不会出现。

扩展数据网格

    public class ReACTDataGrid : DataGrid
    {
        public bool IsFromChildWindow { get; set; }

        private IEnumerable _ItemsSource;
        public IEnumerable ItemsSource
        {
            get { return _ItemsSource; }
            set
            {
                _ItemsSource = value;
                base.ItemsSource = value;

                if (_ItemsSource.IsNullOrEmpty())
                    VisualStateManager.GoToState(this, "HasNoItems", false);
                else
                    VisualStateManager.GoToState(this, "HasItems", false);
            }
        }
    }

XAML样式

    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="data:DataGrid">
                <!--<Grid Background="{Binding Converter={StaticResource ThemeColorConverter}, ConverterParameter=Sub_Brush}" x:Name="Root">-->
                <Grid Background="White" x:Name="Root">
                    <vsm:VisualStateManager.VisualStateGroups>
                        <vsm:VisualStateGroup x:Name="EmptyMsg">
                            <vsm:VisualState x:Name="HasNoItems">
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="EmptyCollectionMsg" Storyboard.TargetProperty="(UIElement.Visibility)">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <Visibility>Visible</Visibility>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </vsm:VisualState>
                            <vsm:VisualState x:Name="HasItems">
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="EmptyCollectionMsg" Storyboard.TargetProperty="(UIElement.Visibility)">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <Visibility>Collapsed</Visibility>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </vsm:VisualState>
                        </vsm:VisualStateGroup>
                    </vsm:VisualStateManager.VisualStateGroups>
                    <Grid.Resources>
                        <ControlTemplate x:Key="TopLeftHeaderTemplate" TargetType="dataPrimitives:DataGridColumnHeader">
                            <Grid Margin="1">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="Auto" />
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto" />
                                    <ColumnDefinition Width="*" />
                                    <ColumnDefinition Width="Auto" />
                                </Grid.ColumnDefinitions>
                                <Rectangle x:Name="Background" Opacity="0.65" Grid.ColumnSpan="3" Grid.RowSpan="3">
                                    <Rectangle.Fill>
                                        <LinearGradientBrush EndPoint="0.5,1.4" StartPoint="0.5,0">
                                            <GradientStop Color="{Binding Converter={StaticResource ThemeColorConverter}, ConverterParameter=Sub_Color}" Offset="0.75" />
                                            <GradientStop Color="{Binding Converter={StaticResource ThemeColorConverter}, ConverterParameter=Sub_Color}" Offset="1" />
                                        </LinearGradientBrush>
                                    </Rectangle.Fill>
                                </Rectangle>
                                <Border CornerRadius="10,10,40,40" x:Name="Highlight" RenderTransformOrigin="0.5,1" Grid.ColumnSpan="3">
                                    <Border.Background>
                                        <RadialGradientBrush>
                                            <RadialGradientBrush.RelativeTransform>
                                                <TransformGroup>
                                                    <ScaleTransform CenterX="0.5" CenterY="0.5" ScaleX="1.25" ScaleY="2" />
                                                    <TranslateTransform Y="-0.6" />
                                                </TransformGroup>
                                            </RadialGradientBrush.RelativeTransform>
                                            <GradientStop Color="#BFFFFFFF" Offset="0" />
                                            <GradientStop Color="#4CFFFFFF" Offset="1" />
                                        </RadialGradientBrush>
                                    </Border.Background>
                                </Border>
                            </Grid>
                        </ControlTemplate>
                        <ControlTemplate x:Key="TopRightHeaderTemplate" TargetType="dataPrimitives:DataGridColumnHeader">
                            <Grid Margin="1">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="Auto" />
                                </Grid.RowDefinitions>
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="Auto" />
                                    <ColumnDefinition Width="*" />
                                    <ColumnDefinition Width="Auto" />
                                </Grid.ColumnDefinitions>
                                <!-- Set opacity to zero to hide mess above scrollbar -->
                                <Rectangle x:Name="Background" Opacity="0" Grid.ColumnSpan="3" Grid.RowSpan="3">
                                    <Rectangle.Fill>
                                        <LinearGradientBrush EndPoint="0.5,1.4" StartPoint="0.5,0">
                                            <GradientStop Color="{Binding Converter={StaticResource ThemeColorConverter}, ConverterParameter=Main_Color}" Offset="0.75" />
                                            <GradientStop Color="{Binding Converter={StaticResource ThemeColorConverter}, ConverterParameter=Sub_Color}" Offset="1" />
                                        </LinearGradientBrush>
                                    </Rectangle.Fill>
                                </Rectangle>
                                <Border CornerRadius="0,0,40,40" x:Name="Highlight" Opacity="0" RenderTransformOrigin="0.5,1" Grid.ColumnSpan="3">
                                    <Border.Background>
                                        <RadialGradientBrush>
                                            <RadialGradientBrush.RelativeTransform>
                                                <TransformGroup>
                                                    <ScaleTransform CenterX="0.5" CenterY="0.5" ScaleX="1.25" ScaleY="2" />
                                                    <TranslateTransform Y="-0.6" />
                                                </TransformGroup>
                                            </RadialGradientBrush.RelativeTransform>
                                            <GradientStop Color="#BFFFFFFF" Offset="0" />
                                            <GradientStop Color="#4CFFFFFF" Offset="1" />
                                        </RadialGradientBrush>
                                    </Border.Background>
                                </Border>
                            </Grid>
                        </ControlTemplate>
                    </Grid.Resources>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="*" />
                        <RowDefinition Height="Auto" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="Auto" />
                    </Grid.ColumnDefinitions>
                    <dataPrimitives:DataGridColumnHeader x:Name="TopLeftCornerHeader" Width="22" Template="{StaticResource TopLeftHeaderTemplate}" />
                    <dataPrimitives:DataGridColumnHeadersPresenter Grid.Column="1" x:Name="ColumnHeadersPresenter" />
                    <dataPrimitives:DataGridColumnHeader Grid.Column="2" x:Name="TopRightCornerHeader" Template="{StaticResource TopRightHeaderTemplate}" />
                    <Rectangle Grid.ColumnSpan="3" Height="1" x:Name="ColumnHeadersAndRowsSeparator" VerticalAlignment="Bottom" Width="Auto" Fill="#FFDBDCDC" StrokeThickness="1" />
                    <dataPrimitives:DataGridRowsPresenter Grid.ColumnSpan="2" Grid.Row="1" x:Name="RowsPresenter" />
                    <Rectangle Grid.Column="2" Grid.Row="2" x:Name="BottomRightCorner" Fill="{TemplateBinding Background}" />
                    <Rectangle Grid.ColumnSpan="2" Grid.Row="2" x:Name="BottomLeftCorner" Fill="{TemplateBinding Background}" />
                    <ScrollBar Grid.Column="2" Grid.Row="1" Margin="0" x:Name="VerticalScrollbar" Width="18" Orientation="Vertical" />
                    <Grid Grid.Column="1" Grid.Row="2">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="Auto" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <Rectangle x:Name="FrozenColumnScrollBarSpacer" />
                        <ScrollBar Grid.Column="1" Height="18" Margin="0" x:Name="HorizontalScrollbar" Orientation="Horizontal" />
                    </Grid>
                    <TextBlock x:Name="EmptyCollectionMsg" Grid.Row="3" Grid.Column="0" Grid.ColumnSpan="3" VerticalAlignment="Center" HorizontalAlignment="Center" Margin="2" Text="No Data Entered" Visibility="Collapsed"></TextBlock>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>

Answer 1

我怀疑观察到的行为不是由ChildWindow或用户界面中任何位置（通常）引起的。

当我查看对ItemsSource重新定义时，我注意到您在其中放置了一些代码，这些代码需要执行才能触发VisualState更改（并更新基类属性，以尝试将本地值和DependencyProperty保留在同步）。 但这不是DependencyProperties工作方式。 Bindings不会调用setter或getter，而是直接调用SetValue（...）和GetValue（...）（ MSDN ）。 因此，您使用的任何绑定都不会触发派生类中的setter代码。

我不会派生一个新的类并提供整个ControlTemplate几乎重复项，只是为了添加“此处无项目”标志。 仅仅是装饰。 我宁愿用以下方法解决此问题：

<MyFancyView>
    ...
    <DataGrid ItemsSource="{...}">
        <Behaviors>
            <ShowEmptySign/>
        <Behaviors>
    </DataGrid>

</MyFancyView>

和自定义行为

public class ShowEmptySign : Behavior<ItemsControl>
{
    private TextBlock msg;
    ...OnAttached()
    {
        var rootGrid=AssociatedObject.GetDecendant<Grid>();
        msg = new TextBlock(){...};
        rootGrid.Children.Add(msg)
        ((INotifyCollectionChanged)AssociatedObject.Items).CollectionChanged += CheckIfEmpty
        CheckIfEmpty();
    }
    ...CheckIfEmpty()
    {
        if(!AssociatedObject.Items.Any()) Show(); else Hide();
    }
    ...Show()
    {
        msg.Visibility = Visibility.Visible;
    }
}

我检查了MSDN，发现DataGrid不是从ItemsControl派生的。 因此，要实际使用它，必须将其行为更改为使用rowLoaded / rowUnloaded事件而不是collectionChanged事件。

Answer 2

您可以尝试不在加载器中执行状态更改代码，而可以在每次加载或卸载行时执行。 因此，ItemsSource中的任何更改最终都会触发您的代码。

public class ReACTDataGrid : DataGrid
{
    private bool templateApplied;
    protected override void OnApplyTemplate()
    {
        templateApplied = true;
        base.OnApplyTemplate();
        CheckIfItemsEmptyAndUpdateVisualState();
    }

    protected override void OnLoadingRow(DataGridRowEventArgs e)
    {
        if (templateApplied) CheckIfItemsEmptyAndUpdateVisualState();
    }

    protected override void OnUnloadingRow(DataGridRowEventArgs e)
    {
        if (templateApplied) CheckIfItemsEmptyAndUpdateVisualState();
    }

    private void CheckIfItemsEmptyAndUpdateVisualState()
    {
        if (this.ItemsSource.IsNullOrEmpty())
            VisualStateManager.GoToState(this, "HasNoItems", false);
        else
            VisualStateManager.GoToState(this, "HasItems", false);
    }
}