c# - 如何获取滚动查看器的可滚动高度以在交互请求中更新

Question

编辑:我发现实际上是滚动查看器中我的项目控件中的项目呈现器没有正确更新，而不是滚动查看器。我添加了一个答案来反射(reflect)这一点。

我有一个自定义 View 交互请求的简单设置。该 View 包含一个滚动查看器，但如果其中的项目控件具有项目源更新，则滚动查看器的可滚动高度不会更新。相关代码如下。

确认模型:

public class ProfileImportConfirmation : Confirmation
{
    public ObservableCollection<ProfileAcceptPair> PossibleProfiles { get; set; } = new ObservableCollection<ProfileAcceptPair>();
    public ObservableCollection<Profile> ConfirmedProfiles { get; set; } = new ObservableCollection<Profile>();
}

View 模型:

public class ProfileImportPopupViewModel : BindableBase, IInteractionRequestAware
{
    ProfileImportConfirmation _profileImportConfirmation;

    public InteractionRequest<Confirmation> YesNoConfirmationInteractionRequest { get; }

    public DelegateCommand AcceptCommand { get; set; }
    public DelegateCommand CancelCommand { get; set; }

    public ProfileImportPopupViewModel()
    {
        AcceptCommand = new DelegateCommand(Accept);
        CancelCommand = new DelegateCommand(Cancel);
        YesNoConfirmationInteractionRequest = new InteractionRequest<Confirmation>();
    }

    public INotification Notification
    {
        get { return _profileImportConfirmation; }
        set
        {
            if (value is ProfileImportConfirmation confirmation)
            {
                _profileImportConfirmation = confirmation;
                OnPropertyChanged(nameof(Notification));
            }
        }
    }

    public Action FinishInteraction { get; set; }

    void Cancel()
    {
        _profileImportConfirmation.Confirmed = false;
        FinishInteraction();
    }

    void Accept()
    {
        _profileImportConfirmation.Confirmed = true;
        _profileImportConfirmation.ConfirmedProfiles.Clear();
        _profileImportConfirmation.ConfirmedProfiles.AddRange(_profileImportConfirmation.PossibleProfiles.Where(p => p.Accepted).Select(p => p.Profile).ToList());
        if (_profileImportConfirmation.ConfirmedProfiles.Any(p => p.IsRootProfile))
            YesNoConfirmationInteractionRequest.Raise(
                new Confirmation
                {
                    Title = DisplayStrings.AreYouSureLabel,
                    Content = "Proceed?"
                },
                confirmed => FinishInteraction());
        else
        {
            FinishInteraction();
        }
    }
}

查看:

<UserControl 
         MaxHeight="500"
         MinWidth="400"
         d:DataContext="{d:DesignInstance Type=viewModels:ProfileImportPopupViewModel, IsDesignTimeCreatable=False}"
         Loaded="ProfileImportPopup_OnLoaded">

<i:Interaction.Triggers>
    <mvvm:InteractionRequestTrigger SourceObject="{Binding YesNoConfirmationInteractionRequest, Mode=OneWay}">
        <mvvm:PopupWindowAction IsModal="True" CenterOverAssociatedObject="True" WindowStyle="{StaticResource PopupWindow}" WindowStartupLocation="CenterOwner">
            <mvvm:PopupWindowAction.WindowContent>
                <popups:YesNoConfirmationPopup />
            </mvvm:PopupWindowAction.WindowContent>
        </mvvm:PopupWindowAction>
    </mvvm:InteractionRequestTrigger>
</i:Interaction.Triggers>

<Grid Margin="30, 0, 30, 30">
    <Grid.RowDefinitions>
        <RowDefinition Height="50"/>
        <RowDefinition Height="50"/> 
        <RowDefinition Height="*"/>
        <RowDefinition Height="40"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>

    <Label Grid.ColumnSpan="2" Content="{Binding Notification.Title}" HorizontalAlignment="Left" FontFamily="{StaticResource 'Brandon Grotesque Bold'}" FontSize="{StaticResource LargeFontSize}"/>

    <Label Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="2" Content="{Binding Notification.Content}" HorizontalAlignment="Center" VerticalContentAlignment="Center" FontFamily="{StaticResource 'Brandon Grotesque Bold'}" FontSize="{StaticResource LargeFontSize}"/>

    <ScrollViewer x:Name="aoeu" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="2" CanContentScroll="True" VerticalScrollBarVisibility="Auto">
        <ItemsControl ItemsSource="{Binding Notification.PossibleProfiles}" Margin="0, 0, 30, 0">
            <ItemsControl.ItemTemplate>
                <DataTemplate DataType="{x:Type models:ProfileAcceptPair}">
                    <CheckBox Style="{StaticResource RightAlignedCheckBox}" Content="{Binding Name}" IsChecked="{Binding Accepted}" HorizontalContentAlignment="Right"/>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </ScrollViewer>

    <Button Grid.Row="3" Grid.Column="0" HorizontalAlignment="Center" Content="{x:Static resources:DisplayStrings.CancelButton}" Style="{StaticResource ModalWindowButton}" Command="{Binding CancelCommand}" Margin="0" VerticalAlignment="Center"/>
    <Button Grid.Row="3" Grid.Column="1" Content="{x:Static resources:DisplayStrings.OKButton}" Style="{StaticResource ModalWindowButton}" Command="{Binding AcceptCommand}" Margin="0" VerticalAlignment="Center" HorizontalAlignment="Center"/>
</Grid>

似乎项目源更新正常，我可以看到隐藏在滚动查看器下方的新项目元素，但我无法向下滚动到它。

如何让可滚动高度更新？

Answer 1

问题不在于滚动查看器。它是滚动查看器中项目控件中的项目演示者。它没有在项目更改时更新它的高度。

我的解决方案并不理想，但它奏效了。我在后面的代码中为用户控件添加了一个加载的事件处理程序。然后我将项目命名为控件并使用它找到项目演示者子项并调用无效度量。

void Popup_OnLoaded(object sender, RoutedEventArgs e)
        {
            var itemsPresenter = (ItemsPresenter) FindChild(MyItemsControl, typeof(ItemsPresenter));
            itemsPresenter.InvalidateMeasure();
        }

public DependencyObject FindChild(DependencyObject o, Type childType)
            {
                DependencyObject foundChild = null;
                if (o != null)
                {
                    var childrenCount = VisualTreeHelper.GetChildrenCount(o);
                    for (var i = 0; i < childrenCount; i++)
                    {
                        var child = VisualTreeHelper.GetChild(o, i);
                        if (child.GetType() != childType)
                        {
                            foundChild = FindChild(child, childType);
                        }
                        else
                        {
                            foundChild = child;
                            break;
                        }
                    }
                }
                return foundChild;
            }