使用Caliburn Micro时DataGrid的ContextMenu调用ActivateItemAsync失效问题

问题描述 #

我在项目中使用Caliburn Micro框架，此前调用ActivateItemAsync方法一直未出现问题，但现在该方法无法激活我的ActiveItem，相关代码如下：

首先是DashboardMainView代码：

<Grid >
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <Ribbon ...>
    </Ribbon>
    <Grid Grid.Row="1" Background="#E8E8E8">
        <ContentControl x:Name="ActiveItem"  HorizontalAlignment="Stretch" 
                        VerticalAlignment="Stretch">
        </ContentControl>
    </Grid>

对应的DashboardMainViewModel代码：

public class DashboardMainViewModel : Conductor<object>
{
    private IDialogCoordinator dialogCoordinator;

    public DashboardMainViewModel(IDialogCoordinator instance)
    {
        this.dialogCoordinator = instance;
        ActivateItemAsync(new DashboardSummaryViewModel());
    }
    public async Task Execution()
    {
        await ActivateItemAsync(new BasicExecutionViewModel(DialogCoordinator.Instance));
    }
}

上述代码运行正常，可成功激活BasicExecutionView，该视图内包含一个DataGrid和右键上下文菜单。问题出在右键操作环节：右键点击DataGrid弹出菜单，选中对应选项后应该激活新视图，但实际无响应，相关代码如下：

BasicExecutionView的XAML代码：

<Grid >
    <Viewbox Stretch="Fill">
    <DataGrid 
        x:Name="BasicExecutionGrid"
        CanUserSortColumns="True"
        IsReadOnly="True"
        CanUserAddRows="False"
        FontSize="11"
        Height ="800"
        ScrollViewer.CanContentScroll="True" 
        ScrollViewer.VerticalScrollBarVisibility="Auto"
        ScrollViewer.HorizontalScrollBarVisibility="Auto" AutoGeneratingColumn="BasicExecutionGrid_AutoGeneratingColumn">
        <DataGrid.ColumnHeaderStyle>
            <Style TargetType="DataGridColumnHeader">
                <Setter Property="ContentTemplate">
                    <Setter.Value>
                        <DataTemplate>
                            <TextBlock TextWrapping="Wrap"
                                       Text="{Binding}" 
                                       HorizontalAlignment="Center" 
                                       VerticalAlignment="Center"></TextBlock>
                        </DataTemplate>
                    </Setter.Value>
                </Setter>
                <Setter Property="HorizontalContentAlignment" Value="Center" />
                <Setter Property="Background" Value="LightSteelBlue"/>
                <Setter Property="FontSize" Value="12"/>
                <Setter Property="FontWeight" Value="Bold"/>
                <Setter Property="Height" Value="45"/>
            </Style>
        </DataGrid.ColumnHeaderStyle>
            <DataGrid.ContextMenu>
                <ContextMenu>
                    <MenuItem Header="Details" 
                              Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}, Path=DataContext.ActivateCellDetailsView}"
                              >
                    </MenuItem>
                </ContextMenu>
            </DataGrid.ContextMenu>
        </DataGrid>
    </Viewbox>
</Grid>

对应的BasicExecutionViewModel代码：

class BasicExecutionViewModel : Conductor<object>
{
    private IDialogCoordinator dialogCoordinator;
    private RelayCommand activateCellDetailsView { get; set; }

    public BasicExecutionViewModel(IDialogCoordinator instance)
    {
        this.dialogCoordinator = instance;
    }

    public ICommand ActivateCellDetailsView
    {
        get
        {
            if (activateCellDetailsView == null)
            {
                activateCellDetailsView = new RelayCommand(async p=> await ActivateCellView());
            }
            return activateCellDetailsView;
        }
    }
    public async Task ActivateCellView()
    {
        await ActivateItemAsync(new CellDetailsExecutionViewModel());
    }
}

调试发现代码可正常进入ActivateCellView()执行，输出窗口也显示ActiveItem已赋值为CellDetailsExecutionViewModel对象，但界面仍然显示BasicExecutionView。

修复方案 #

问题根因为Conductor<object>使用错误，修复步骤如下：

• 将DashboardMainViewModel的继承关系修改为：

DashboardMainViewModel: Conductor<object>.Collection.OneActive

• BasicExecutionViewModel也同步修改继承关系：

BasicExecutionViewModel: Conductor<object>.Collection.OneActive

• 修改ActivateCellView()方法代码为：

public async Task ActivateCellView()
{
    CellDetailsExecutionViewModel cellDetailsExecutionViewAcvtivate = new CellDetailsExecutionViewModel();
    var parentConductor = (Conductor<object>.Collection.OneActive)(this.Parent);
    await parentConductor.ActivateItemAsync(cellDetailsExecutionViewAcvtivate);
}

修改后功能运行正常。

内容的提问来源于stack exchange，提问作者Pepe