如何获得滚动查看器的可滚动高度以在交互请求中更新

Question

编辑：我发现实际上是我的项目控件中的项目演示者在滚动查看器中而不是在滚动查看器中没有正确更新。 我添加了一个答案来反映这一点。

我为自定义视图交互请求进行了简单的设置。 该视图包含一个滚动查看器，但是如果滚动查看器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>();
}

视图模型：

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();
        }
    }
}

视图：

<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>

看来item来源正在更新，我可以看到隐藏在滚动查看器下方的新item元素，但无法向下滚动。

如何获取可滚动的高度以进行更新？

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。 它不是在更改项目时更新高度。

我的解决方案不是理想的，但是有效。 我在后面的代码中为用户控件添加了已加载的事件处理程序。 然后，我将项目控件命名为，并使用该控件找到项目展示者子级，并称为无效度量。

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;
            }