Windows 7 Multitouch Application Development (Part - II)

Kunal2383
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In my last article Windows 7 Multitouch Application Development (Part - I), I described about how to handle multitouch image manipulation in Windows 7 which gives a very basic idea on the multitouch development. That code uses multitouch manipulation for the entire screen. If there are multiple images in the screen this will raise event for all.
Introduction
In my last article Windows 7 Multitouch Application Development (Part - I), I described about how to handle multitouch image manipulation in Windows 7 which gives a very basic idea on the multitouch development. That code uses multitouch manipulation for the entire screen. If there are multiple images in the screen this will raise event for all. In this post, I will show you how to manage multitouch events for all the images separately.
Touch-ID Overview

For this we have to assign a unique touch-id for each finger on the screen. As long as the finger touches the screen the associated touch-id will remain same for that particular finger. If the user releases his finger the system will release the touch-id & that can be again assign by the system automatically on next touch. So, how can we get the touch-id? You can get the same from the StylusEventArgs (i.e. args.StylusDevice.Id). The stylus device will automatically generate this ID for each touch, only thing is you have to assign it with the respective finger touch.

XAML Implementation

First of all, we will create an UserControl which will consist of a single Image & XAML code for it’s RenderTransform. The same thing we did in the previous post which was inside the Window, but here it will be inside the UserControl (Picture class). Create a DependencyProperty to assign the ImageLocation dynamically.

<UserControl x:Class="Windows7MultitouchDemo.Picture"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<
Image Source="{Binding Path=ImageLocation}" Stretch="Fill" Width="Auto"
Height="Auto" RenderTransformOrigin="0.5, 0.5">
<
Image.RenderTransform>
<
TransformGroup>
<
RotateTransform x:Name="trRotate"/>
<
ScaleTransform x:Name="trScale"/>
<
TranslateTransform x:Name="trTranslate"/>
</
TransformGroup>
</
Image.RenderTransform>
</
Image>
</
UserControl>
Code Implementation

To track the multi-touch simultaneously for the above “Picture” usercontrol, you can use the PictureTracker class which comes with the Windows 7 Training Kit. You can download it from Microsoft Site. It looks similar to this:


/// <summary>
///
Track a single picture
/// </summary>
public class PictureTracker
{
private Point _prevLocation;
public Picture Picture { get; set; }
public void ProcessDown(Point location)
{
_prevLocation = location;
}
public void ProcessMove(Point location)
{
Picture.X += location.X - _prevLocation.X;
Picture.Y += location.Y - _prevLocation.Y;
_prevLocation = location;
}
public void ProcessUp(Point location)
{
//Do Nothing, We might have another touch-id that is
//still down
}
}

Now, we have to store all the active touch-ids associated with the PictureTracker class. So, we will use a dictionary for that. We will use the same PictureTrackerManager class which again comes with the Windows 7 Training Kit.

private readonly Dictionary<int, PictureTracker> _pictureTrackerMap;

Create an instance of the PictureTrackerManager class inside your Window1.xaml.cs & register the stylus events with the PictureTrackerManager events. So now whenever a touch occurs on the Picture, the PictureTrackerManager will first find the associated touch-id for the respective instance and raise event to process the same.

//Register for stylus (touch) events
StylusDown += _pictureTrackerManager.ProcessDown;
StylusUp += _pictureTrackerManager.ProcessUp;
StylusMove += _pictureTrackerManager.ProcessMove;
Conclusion
This is a sample code of implementation, you can modify it as per your need to meet your business need.


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About the Author

Kunal2383
Full Name: Kunal Chowdhury
Member Level:
Member Status: Member
Member Since: 3/1/2010 12:38:55 PM
Country: India
Thanks & Regards, Kunal Chowdhury | http://www.kunal-chowdhury.com | http://twitter.com/kunal2383
http://www.kunal-chowdhury.com
He is currently working as a Silverlight application developer. Has a very good skill over C#, XAML, Silverlight & WPF. He has a good working experience in Windows 7 application (including Multitouch) development. During his professional career he worked in various technologies & delivered quality output. He never hesitates to take up challenges & work on the latest technologies in Microsoft platform. He attended various software development competition & achieved different awards. He is presently focusing on the RIA (Silverlight & WPF) & willing to become a Technology Specialist in Microsoft platform. Learning newer things, Blog posting & helping others in forums is one of his regular activity. Specialties: Silverlight Application Development, WPF Application Development, Windows 7 Application Development

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Comments or Responses

Posted by: Nivaas on: 11/19/2010 | Points: 25
can you help me out,
where do you putt is all.
part 1 ig got, but when part 2 start I lose it.
please help, i'm a beginner in c#
Posted by: Sazzadur on: 6/14/2011 | Points: 25
Is it possible to get the source code as a file (just like Part I). I am a beginner. I will be grateful if you kindly supply the whole file.

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