How to make the Silverlight ScrollViewer scroll to show a child control with focus

scrollviewersilverlight

I have a ScrollViewer which contains a Grid with multiple controls in it. The user can tab through the controls, but eventually they tab to a control that isn't in view – so they have to manully scroll to make the control visible again.

Is there any way to make the ScrollViewer scroll automatically so that the focussed control is always visible. Failing that, is there any way I can make this work, short of listening to a GotFocus event on every control and then scrolling the ScrollViewer to make the control visible?

At present I'm using Silverlight 2.

Best Answer

I tested this using Silverlight 3. I am not sure about SL2.

This is my XAML:

<ScrollViewer Height="200" Width="200" KeyUp="ScrollViewer_KeyUp">
    <StackPanel>
        <Button Content="1" Height="20" />
        <Button Content="2" Height="20" />
        <Button Content="3" Height="20" />
        <Button Content="4" Height="20" />
        <Button Content="5" Height="20" />
        <Button Content="6" Height="20" />
        <Button Content="7" Height="20" />
        <Button Content="8" Height="20" />
        <Button Content="9" Height="20" />
    <Button Content="10" Height="20" />
        <Button Content="11" Height="20" />
        <Button Content="12" Height="20" />
        <Button Content="13" Height="20" />
        <Button Content="14" Height="20" />
        <Button Content="15" Height="20" />
        <Button Content="16" Height="20" />
        <Button Content="17" Height="20" />
        <Button Content="18" Height="20" />
        <Button Content="19" Height="20" />
        <Button Content="20" Height="20" />
    </StackPanel>
</ScrollViewer>

And this is the code-behind:

private void ScrollViewer_KeyUp(object sender, KeyEventArgs e)
{
    ScrollViewer scrollViewer = sender as ScrollViewer;
    FrameworkElement focusedElement = FocusManager.GetFocusedElement() as FrameworkElement;
    GeneralTransform focusedVisualTransform = focusedElement.TransformToVisual(scrollViewer);
    Rect rectangle = focusedVisualTransform.TransformBounds(new Rect(new Point(focusedElement.Margin.Left, focusedElement.Margin.Top), focusedElement.RenderSize));
    double newOffset = scrollViewer.VerticalOffset + (rectangle.Bottom - scrollViewer.ViewportHeight);
    scrollViewer.ScrollToVerticalOffset(newOffset);
}

What I did was to click on Button #1 and tab until I get to Button #20. It worked for me. Give it a try and let me know how it works for you.

Related Solutions

Wpf – XAML ScrollViewer scroll bar hidden issue (Silverlight)

Ok I don’t know why the above doesn’t work, but as a workaround I just restructure the page so its behaves the same. That works:

<UserControl x:Class="SilverlightApplication7.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
mc:Ignorable="d"
>
<Grid 
    ShowGridLines="True" 
    HorizontalAlignment="Stretch" 
    VerticalAlignment="Stretch"
>
    <Grid.RowDefinitions>
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition x:Name="DealBarColumn" Width="Auto"></ColumnDefinition>
        <ColumnDefinition x:Name="MarketViewerColumn" Width="Auto"></ColumnDefinition>
        <ColumnDefinition x:Name="DealEditorColumn" Width="*" ></ColumnDefinition>
    </Grid.ColumnDefinitions>

    <ContentControl 
        x:Name="DealBarRegionContentControl"
        Grid.Column="0" 
        VerticalContentAlignment="Stretch"
        HorizontalAlignment="Stretch"
        Margin="0">
        <TextBlock Text="DealBarRegion" Width="150" />
    </ContentControl>

    <ContentControl 
        Grid.Column="1" 
        VerticalContentAlignment="Stretch"
        HorizontalAlignment="Stretch"
        HorizontalContentAlignment="Stretch">
        <Border Background="#FF9AF172">
            <TextBlock Text="MarketViewerRegion"  Width="150"  />
        </Border>
    </ContentControl>

    <Grid
        Grid.Column="2" >
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <ContentControl 
            Grid.Row="0"
            HorizontalAlignment="Stretch"
            HorizontalContentAlignment="Stretch" >
            <Border Background="#FFC1FC9F">
                <TextBlock Text="DealHeaderRegion"  />
            </Border>
        </ContentControl>

        <Grid 
            Grid.Row="1"     
            HorizontalAlignment="Stretch"
            VerticalAlignment="Stretch"
            >
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"></ColumnDefinition>
                <ColumnDefinition Width="Auto"></ColumnDefinition>
            </Grid.ColumnDefinitions>
            <ContentControl 
                Grid.Column="0"
                VerticalAlignment="Top"
                HorizontalContentAlignment="Stretch" 
                VerticalContentAlignment="Stretch">
                <Border Background="MistyRose" >
                    <TextBlock Text="DealEditorRegion" />
                </Border>
            </ContentControl>
            <ContentControl 
                Grid.Column="1"
                x:Name="InfoRegionControl" 
                VerticalContentAlignment="Stretch"
                HorizontalAlignment="Right">
                <!-- without the padding here you can't see the scroll bar at all !! Its like the 
                scroll ScrollViewer isn't correctly calculating its width to include the scroll bar,
                or the grid isn't sizing at the points its visible??-->
                <Border Padding="0,0,9,0" MinWidth="200" x:Name="DealInfoControlPlaceHolder">
                    <ScrollViewer  
                        HorizontalAlignment="Stretch" 
                        HorizontalContentAlignment="Stretch"
                        VerticalScrollBarVisibility="Auto" 
                        HorizontalScrollBarVisibility="Auto"  
                        >
                        <StackPanel x:Name="ScrollContentPlaceHolder">
                            <Button Click="Button_Click" Content="Rezize Column" x:Name="ResizeButton" />
                        </StackPanel>
                    </ScrollViewer>
                </Border>
            </ContentControl>
        </Grid>
    </Grid>
</Grid>

XAML: make a ScrollViewer show scrollbars when the ScaleTransform of a child object gets big

Yeah, the problem is that there is no LayoutTransform in Silverlight. There are some workarounds to this problem listed here.

The idea here is to provide an intermediate canvas that gets resized and as a result, resizes the scrollable area. For example, if I have the following XAML:

<Grid x:Name="LayoutRoot">
    <Grid.RowDefinitions>
        <RowDefinition Height="200" />
        <RowDefinition Height="25" />
    </Grid.RowDefinitions>
        <ScrollViewer Grid.Row="0" x:Name="sc" VerticalScrollBarVisibility="Auto" 
                      HorizontalScrollBarVisibility="Auto" Width="200" Height="200" >
        <Canvas x:Name="sizer" Width="200" Height="200">
            <Rectangle x:Name="gradientRect" Width="200" Height="200">
            <Rectangle.RenderTransform>
                <ScaleTransform ScaleX="1" ScaleY="1"/>
            </Rectangle.RenderTransform>
                <Rectangle.Fill>
                    <LinearGradientBrush StartPoint="0,0" EndPoint="1,1">
                        <GradientStop Color="Red" Offset="0.1"/>
                        <GradientStop Color="Yellow" Offset="0.5"/>
                        <GradientStop Color="Red" Offset="0.9"/>
                    </LinearGradientBrush>
                </Rectangle.Fill>
            </Rectangle>
        </Canvas>
    </ScrollViewer>
    <Button Grid.Row="1" Content="Multiply by Two" Click="ScaleRect" Width="100" Height="25"></Button>
</Grid>

You'll notice that I put the <Canvas x:Name="sizer"/> between the <ScrollViewer/> and <Rectangle/> and the click event of ScaleRect in the <Button/>.

The ScaleRect sub simply scales the rectangle by 2. That value is then used to change the sizer Width and Height, thus updating the ScrollViewer's scrollbars. Here's the sub for ScaleRect:

Private Sub ScaleRect(ByVal sender As Object, ByVal e As RoutedEventArgs)
    Dim zoom As Double = 2.0
    Dim scaleX = gradientRect.RenderTransform.GetValue(ScaleTransform.ScaleXProperty)
    Dim scaleY = gradientRect.RenderTransform.GetValue(ScaleTransform.ScaleYProperty)
    gradientRect.RenderTransform.SetValue(ScaleTransform.ScaleXProperty, scaleX * zoom)
    gradientRect.RenderTransform.SetValue(ScaleTransform.ScaleYProperty, scaleY * zoom)
    sizer.Height *= zoom
    sizer.Width *= zoom
End Sub

Best Answer

Related Solutions

Wpf – XAML ScrollViewer scroll bar hidden issue (Silverlight)

XAML: make a ScrollViewer show scrollbars when the ScaleTransform of a child object gets big

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