expand event?

[robert]

Hello, thank you for your last help. I still have a last question to my evaluation related to the gantt control.
Is there a possibility to get the tree-column expanded event in code behind? The goal is to load huge data on demand when
e.g. summary task is expanding on table side. For us this is a very important feature and basically neccessary.
Are there any plans or possibilitys to resolve this issue for our requirements?

Best Regards ... Robert

[Polya]

Hello Robert,

Expanding/Collapsing of GanttTasks in RadGanttView can be achieved programmatically by using the RadGanttView.ExpandCollapseService.
For example, if we want to Collapse all items on a button click we can use the following code in the Button_OnClick(object sender, RoutedEventArgs e):

if (button.IsChecked == true)
{
    foreach (var gt in this.GanttView.TasksSource as IList<GanttTask>)
    {
        foreach (var child in gt.Children)
        {
            this.GanttView.ExpandCollapseService.CollapseItem(child);
        }

        this.GanttView.ExpandCollapseService.CollapseItem(gt);
    }

    return;
}

Similarly, we can use this.GanttView.ExpandCollapseService.ExpandItem(gt);
You can use this approach when the synchronization with your source is happening.
Hopefully this helps and is suitable for your scenario. 

Regards,
Polya
Telerik

 

 

[robert]

Hello Polya,
thank you for your answer, but i not mean to expand and collapse items in code behind like in your sample.
I mean how determine on gridside when user is expanding a summary task. My goal is to
load the data from the childnodes later and insert these as children related to the summary task on demand.

Best Regards .. Robert ...

[Polya]

Hi Robert ,

Thank you for your clarification.
Unfortunately, an expand/collapse state changed event is not available in the current implementation of the RadGanttView.
However, I've included this feature request in our Feedback portal: http://feedback.telerik.com/Project/143/Feedback/Details/138401-introduce-expandcollapsechanged-event where you can track its status and vote to raise its priority.

We apologize for the inconvenience caused.

Regards,
Polya
Telerik

 

 

[Polya]

Hi Robert,

After further investigation I can suggest an alternative event we can subscribe to in order to detect when a GanttTask has been expanded/collapsed.
We should handle the CollectionChanged event of the ExpandCollapseService.HierarchicalCollectionAdapter of the RadGanttView:

this.gantt.ExpandCollapseService.HierarchicalCollectionAdapter.CollectionChanged += HierarchicalCollectionAdapter_CollectionChanged;

private void HierarchicalCollectionAdapter_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
    //implement logic here
}

When the e.NewItems is not null - the task has been expanded and when e.OldItems is not null - the task has been collapsed.

Hopefully this helps and is suitable for your scenario.

Regards,
Polya
Telerik

 

 

[robert]

Hi Polya,

thank you for your further Investigation. With NewItems and OldItems it is possible
to detect the expand/collapsed state, but the CollectionChanged event is raised on every child during
collection is expanding. I need that the event is raised only at once on expand or collapsed.

Regards,
Robert

[Kalin]

Hi Robert,

I tested the event and it was only raised once when GanttTask is expanding/collapsing. I tested it with the latest official release version of the controls. Can you please share some more details about the exact scenario? What version of the control are you using?

I'm looking forward to hearing from you.

Regards,
Kalin
Telerik

 

 

[Richard]

Hi Polya,

very interesting topic. I also need such a event to make something with load on demand.
My Problem is how to use it in MVVM? The
gantt.ExpandCollapseService.HierarchicalCollectionAdapter.CollectionChanged Event seems
to be very special. How can i declare this in XAML (Event to Command) and passing the value from e.NewItems ? 
This would me help for my scenario.

Regards,
Richard

[Kalin]

Hi Richard,

What I can suggest you would to implement a custom attached property that will be hooking to the event and executing a custom command in the ViewModel. So the attached property should be defined the following way:

public class GanttHelper
{
    static RadGanttView myGantt;
    public static bool GetIsEnabled(DependencyObject obj)
    {
        return (bool)obj.GetValue(IsEnabledProperty);
    }

    public static void SetIsEnabled(DependencyObject obj, bool value)
    {
        obj.SetValue(IsEnabledProperty, value);
    }

    // Using a DependencyProperty as the backing store for IsEnabled.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty IsEnabledProperty =
        DependencyProperty.RegisterAttached("IsEnabled", typeof(bool), typeof(GanttHelper), new PropertyMetadata(OnIsEnabledChanged));

    private static void OnIsEnabledChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (e.NewValue != e.OldValue)
        {
            myGantt = d as RadGanttView;
            myGantt.ExpandCollapseService.HierarchicalCollectionAdapter.CollectionChanged -= HierarchicalCollectionAdapter_CollectionChanged;
            myGantt.ExpandCollapseService.HierarchicalCollectionAdapter.CollectionChanged += HierarchicalCollectionAdapter_CollectionChanged;
        }
    }

    static void HierarchicalCollectionAdapter_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        (myGantt.DataContext as ViewModel).CustomCommand.Execute(e.NewItems);
    }
}

Enable the helper the following way:

<telerik:RadGanttView x:Name="xGanttView" local:GanttHelper.IsEnabled="True">

After the event is fire the CustomCommand from the ViewModel will be executed with the new items as a parameter.

Hope this helps.

Regards,
Kalin
Telerik