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Detecting Gestures on a Multitouch Screen (Windows Phone)

XNA Game Studio 4.0

This topic demonstrates how to detect and use multitouch gestures in an XNA game.

Complete Sample

The code in this topic shows you the technique for detecting and using multitouch gestures. You can download a complete code sample for this topic, including full source code and any additional supporting files required by the sample.

XNA Game Studio 4.0 supports multitouch gesture-based input on Windows Phone 7. The primary class that provides this support is TouchPanel, which provides the ability to:

  • Designate which gestures should be detected.
  • Query to see if any gestures are available for processing.
Ff827740.note(en-us,XNAGameStudio.40).gifNote
Gesture support is provided as a conventient subset of the features possible on a multitouch input device. For more information about general multitouch programming, see Working with Touch Input (Windows Phone).

Detecting Gestures on a Multitouch Screen

To enable gesture support and detect gestures in a Windows Phone game

  1. Set the gestures to enable with TouchPanel.EnabledGestures. This can be one value, or a combination of values, in the GestureType enumeration. Performance can be decreased by enabling all gestures, so it is a good practice to enable only the gestures you'll be using in your game.

  2. During your game loop, check to see if any gestures are available with TouchPanel.IsGestureAvailable. When IsGestureAvailable is false, there are no more gestures in the queue.

  3. If gestures are available, call TouchPanel.ReadGesture to get a GestureSample that contains the data for the gesture.

Ff827740.note(en-us,XNAGameStudio.40).gifNote
Some gestures will be preceded by another gesture that begins the gesture. For instance, a DoubleTap gesture is always preceded by a Tap gesture. For more information about the various gesture types supported, see GestureType.

Example

The following code illustrates the procedure for detecting gestures on a multitouch screen.

  • Enabling gestures in the game's constructor:

    // set up touch gesture support: make vertical drag and flick the
    // gestures that we're interested in.
    TouchPanel.EnabledGestures =
        GestureType.VerticalDrag | GestureType.Flick;
    
  • Detecting gestures in the game's Update method:

    // get any gestures that are ready.
    while (TouchPanel.IsGestureAvailable)
    {
        GestureSample gs = TouchPanel.ReadGesture();
        switch (gs.GestureType)
        {
            case GestureType.VerticalDrag:
                // move the poem screen vertically by the drag delta
                // amount.
                poem.offset.Y -= gs.Delta.Y;
                break;
    
            case GestureType.Flick:
                // add velocity to the poem screen (only interested in
                // changes to Y velocity).
                poem.velocity.Y += gs.Delta.Y;
                break;
        }
    }
    

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