IPhone like scrolling on Silverlight ListBox

Question

Hi!

I need a listbox with IPhone-like functionality for Silverlight. That is, animated scrolling, and click and drag to scroll. Scrolling will continue a bit after the mouse up event based on the "speed" of the dragging. I've search and found no control vendors providing this. So question is how should I build it? I need some hints to get started.

There's two parts to this question:

Part 1, How to get the animated scrolling of the listbox.

Part 2, How to build a "draggable" scrolling, I guess I should put a canvas on top and track the mouseevent, and simulate some physics. Some hints here would have been great.

Thanks Larsi.

Answer 1

This will be easier in Silverlight 3 than Silverlight 2, but not impossible in 2.

This video from MIX 09, Building Microsoft Silverlight Controls, should help you.

Answer 2

A while ago I made a control that did something like this. All I did was put a stackpanel inside a canvas. Just adjust the canvas.top of the entire stackpanel on a mousemove (while mouse is pressed). To animate the scrolling after a mouseup, you really just need to track the amount moved and apply an animation to the canvas.top property.

Answer 3

<ScrollViewer x:Name="sv1" Width="500" Height="285">
   <StackPanel x:Name="sp1" Width="450" Height="285">
   </StackPanel>
</ScrollViewer>

By setting pos. and neg. margins to the stackpanel inside the scrollviewer you can create a scroll effect.

onScroll_Up()
{
  //Change this based on your scrollviewer dimension
  if (this.sv1.ScrollableHeight < 300)
  {
    Thickness thickness = this.sp1.Margin;
    thickness.Top += 50;
    this.sv1.SetValue(StackPanel.MarginProperty, thickness);
  }   
}


onScroll_Down()
{
  if (this.sv1.ScrollableHeight > 1)
  {
    Thickness thickness = this.sp1.Margin;
    thickness.Top += -50;
    this.sv1.SetValue(StackPanel.MarginProperty, thickness);
  }
}

Answer 4

Here's a really nice complete sample for WPF that does both drag scrolling and automatic flick/inertia scrolling. I'm not sure what if anything would need to be changed to make it work in Silverlight.

http://sachabarber.net/?p=628

Just a note that as-is you can't click and drag the view if you click on a child (e.g. buttons) that capture the mouse input. I actually ended up modifying this sample so you could still drag scroll when you click on children, while still allowing children to accept mouse input when not drag scrolling.

Answer 5

Another post from Sacha Barber's website:

http://sachabarber.net/?p=481

Jeremiah Morrill shares code that implements animated scrolling with inertia in a custom ContentControl (templated with an included ScrollViewer)