Hierachical grid move expanded row to top

[Maarten]

Hi,

Our BU would like that if a row is expaned in a hierchical grid, that grid scroll vertically so that the expanded row becomes the first visible row of the grid. Is this possible?

Many thx!

Maarten

[Svett]

Hello Maarten,

Thank you for writing.

You can achieve that by using the ChildViewExpanded event in co-operation with GridTraverser in the following manner:

void radGridView1_ChildViewExpanded(object sender, Telerik.WinControls.UI.ChildViewExpandedEventArgs e)
{
    GridRowElement rowElement = this.radGridView1.TableElement.GetRowElement(e.ChildRow);

    if (rowElement != null)
    {
        GridTraverser traverser = new GridTraverser(this.radGridView1.TableElement.RowScroller.Traverser as GridTraverser);
        traverser.ProcessHierarchy = true;
        traverser.Reset();
        int value = 0;

        while (traverser.MoveNext())
        {
            if (traverser.Current.PinPosition == PinnedRowPosition.None)
            {
                value += this.radGridView1.TableElement.ViewElement.RowLayout.GetRowHeight(traverser.Current);
            }

            if (traverser.Current == e.ParentRow)
            {
                break;
            }
        }

        RadScrollBarElement vScroll = this.radGridView1.TableElement.VScrollBar;

        if (value < vScroll.Minimum)
        {
            value = vScroll.Minimum;
        }

        if (value > vScroll.Maximum)
        {
            value = vScroll.Maximum;
        }

        vScroll.Value = value;
    }
}

I hope this helps.
 
Greetings,
Svett
the Telerik team

[Maarten]

Hi,

Thx for the code example!

However I noticed two items:
 - The example only works correct if only one row is expanded. If a user already expanded one row and expands a second the rowheight calculation is no longer correct. Is there a method to calculate the rowheight taking into account the subgrid height?

- If a user selects the + sign to expand a row this parent row is moved to the top but is no longer selected. For the user quite confusing... I already tried to force the parentrow to be the selected one but I think another event counteracts this. Any ideas?

Many thx!

Maarten

[Svett]

Hello Maarten,

Regarding your questions:

1. I did not manage to reproduce the issue. I am enclosing a recorded video that demonstrates my approach. Could you point me what I missed? Note that you need installed web browser and flash plugin to watch it.

2. You should modify the ChildViewExpanded event handler in the following way to make the expanded row current:

void radGridView1_ChildViewExpanded(object sender, Telerik.WinControls.UI.ChildViewExpandedEventArgs e)
{
    GridRowElement rowElement = this.radGridView1.TableElement.GetRowElement(e.ChildRow);

    if (rowElement != null)
    {
        GridTraverser traverser = new GridTraverser(this.radGridView1.TableElement.RowScroller.Traverser as GridTraverser);
        traverser.ProcessHierarchy = true;
        traverser.Reset();
        int value = 0;

        while (traverser.MoveNext())
        {
            if (traverser.Current.PinPosition == PinnedRowPosition.None)
            {
                value += this.radGridView1.TableElement.ViewElement.RowLayout.GetRowHeight(traverser.Current);
            }

            if (traverser.Current == e.ParentRow)
            {
                break;
            }
        }

        RadScrollBarElement vScroll = this.radGridView1.TableElement.VScrollBar;

        if (value < vScroll.Minimum)
        {
            value = vScroll.Minimum;
        }

        if (value > vScroll.Maximum)
        {
            value = vScroll.Maximum;
        }

        vScroll.Value = value;
        e.ParentRow.IsCurrent = true;
    }
}

Regards,
Svett
the Telerik team

[Wesley]

I think the problem in the proposed solution is that the scroll position is calculated by adding the height of data rows.
The following heights are not included:

• header row height of subgrid
• filter row height of subgrid
• padding/margin around subgrid
• ... ??

So when you start to expand multiple rows, the calculated scroll position gets more and more out of position

[Svett]

Hi Wesley,

You do not need to include the height of the header and filter rows, because they are pinned rows. Hence, they do not determine the scroll bar calculation. Regarding, the padding/margin values are included in the row height.

Greetings,
Svett
the Telerik team

[Wesley]

Hi,
I think the height of the pinned rows of the child grids need to be included. Only the pinned rows of the main grid can be excluded.
I do this by traversing all row types and only counting the height of a pinned row if its hierarchy is greather than 1:

void TransactionGridViewChildViewExpanded(object sender, ChildViewExpandedEventArgs e)
{
    //Make sure an expanded row is shown on top.
    if (!e.IsExpanded) return;

    var traverser = new GridTraverser(transactionGridView.TableElement.RowScroller.Traverser as GridTraverser) { ProcessHierarchy = true, TraversalMode = GridTraverser.TraversalModes.AllRows };
    traverser.Reset();

    int value = 0;
    while (traverser.MoveNext())
    {
        if (traverser.Current == e.ParentRow)
        {
            break;
        }

        if (traverser.Current.PinPosition == PinnedRowPosition.None || traverser.Current.HierarchyLevel > 1)
        {
            value += transactionGridView.TableElement.ViewElement.RowLayout.GetRowHeight(traverser.Current);
        }
    }

    RadScrollBarElement vScroll = transactionGridView.TableElement.VScrollBar;

    if (value < vScroll.Minimum) value = vScroll.Minimum;
    if (value > vScroll.Maximum) value = vScroll.Maximum;
    vScroll.Value = value;

    e.ParentRow.IsCurrent = true;
}

This produced a better result, but there still is a problem:
An inner grid can also have a scrollbar on its own (see screenshot). The code above will add the heigth of all rows of the inner grid instead of excluding invisible rows (due to the inner scrollbar). This results in a scroll position that is wrong.
I think that if it would be possible to get the actual height of a row including its child rows, I would be able to implement what I want

[Svett]

Hi Maarten,

Unfortunately, the proposed solution does not work for more than two levels of hierarchy. I have tried to change it in a way to support all levels of hierarchy, but due to the dynamic calculations of the elements sizes during scrolling I was not able to do that. 

Kind regards,
Svett
the Telerik team