从任务中执行的 ViewModel 方法报告进度

Question

我正在尝试报告任务中执行的 ViewModel (MVVM Light) 方法的进度。 ProgressViewModel 包含一个 ProgressModel 属性，它提供描述当前状态的属性。这些属性绑定到 Xceed BusyIndicator。到目前为止，一切都很好。但它没有按预期工作。 ProgressModel.IsRunning 绑定到 BusyIndiciator.IsBusy 并切换可见性 - 有效。 ProgressModel.Description 和 ProgressModel.Percentage 绑定到 TextBlock.Text/ProgressBar.Value - 但它们未更新...

所以...因为 IsRunning 有效，Description 和 Progress 有什么问题...？

// Model
public sealed class ProgressModel: ObservableObject
{
    private string m_description;
    private float m_percentage;
    private bool m_running;

    public string Description
    {
        get { return m_description; }
        set { Set(ref m_description, value); }
    }
    public float Percentage
    {
        get { return m_percentage; }
        set { Set(ref m_percentage, value); }
    }
    public bool IsRunning
    {
        get { return m_running; }
        set{Set(ref m_running, value);}
    }

    public void Initiate()
    {
        Description = string.Empty;
        Percentage = 0;
        IsRunning = true;
    }
}
// Command
private void DownloadWatch()
{
    DispatcherHelper.UIDispatcher.Invoke(() =>
    {
        Progress.Initiate();
    });
    using (var watch = new PolarWatch())
    {
        watch.Connect();
        for (var i = 0; i < watch.Sessions.Count; i++)
        {
            DispatcherHelper.UIDispatcher.Invoke(() =>
            {
                Progress.Description = $"Writing session data for '{session.DateTime}'...";
            });
        }
    }
    DispatcherHelper.UIDispatcher.Invoke(() =>
    {
        Progress.IsRunning = false;
    });
}
// View
<xctk:BusyIndicator Name="Busy" IsBusy="{Binding Progress.IsRunning}">
    <xctk:BusyIndicator.BusyContentTemplate>
        <DataTemplate>
            <Grid Width="150">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*" />
                    <ColumnDefinition Width="Auto" />
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition />
                    <RowDefinition />
                </Grid.RowDefinitions>
                <TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding Progress.Description}"/>
                <ProgressBar Grid.Row="1" Grid.Column="0" Value="{Binding Progress.Percentage}" Height="14" Margin="0,5,0,0"/>
            </Grid>
        </DataTemplate>
    </xctk:BusyIndicator.BusyContentTemplate>
    <xctk:BusyIndicator.ProgressBarStyle>
        <Style TargetType="ProgressBar">
            <Setter Property="Visibility" Value="Collapsed"/>
        </Style>
    </xctk:BusyIndicator.ProgressBarStyle>

Answer 1

ItemTemplate 中根元素的 DataContext 与控件本身的 DataContext 不同。试试这个：

<TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding DataContext.Progress.Description, RelativeSource={RelativeSource AncestorType=xctk:BusyIndicator}}"/>
<ProgressBar Grid.Row="1" Grid.Column="0" Value="{Binding DataContext.Progress.Percentage,RelativeSource={RelativeSource AncestorType=xctk:BusyIndicator}}" Height="14" Margin="0,5,0,0"/>

或设置Grid的DataContext:

<Grid Width="150" DataContext="{Binding DataContext.Progress, RelativeSource={RelativeSource AncestorType=xctk:BusyIndicator}}">
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*" />
        <ColumnDefinition Width="Auto" />
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
        <RowDefinition />
        <RowDefinition />
    </Grid.RowDefinitions>
    <TextBlock Grid.Row="0" Grid.Column="0" Text="{Binding Description}"/>
    <ProgressBar Grid.Row="1" Grid.Column="0" Value="{Binding Percentage}" Height="14" Margin="0,5,0,0"/>
</Grid>

从任务中执行的 ViewModel 方法报告进度

Reporting progress from ViewModel method executed in a Task

c#

wpf

progress

mvvm