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Android - Basic Steps (Gestures)

Gestures

Android use two classes

  • MotionEvent
    • Represent the movements
  • TouchHandling
    • To use the movement in the application

MotionEvent

The structure is
  • Action Code
    • State change that occurred
  • Action Values
    • Position and movement properties (time, source, location)
Rules
  • Touches go down one at a time
  • touches move as a group
  • Come up one at a time or are cancelled
Methods
  • getActionMasked()
    • Return the action code associated with the motion event getActionIndex
  • getActionIndex()
    • Return the index of the pointer associated with the action code
  • getPointerId(int)
    • return the stable id of the pointer

Pointer

  • Individual touch sources
  • Each pointer has a unique ID as long as it is active
  • Each pointer has an index within the event
  • MotionEvent can refer to multiple pointers

GestureDetector 

Recognize common touch gestures (single tap, double tap, fling)

To use it:

  • Create a GestureDector that implements OnGestureListener interface
  • When the activity is touch will recieve calls  to onTouchEvent()
  • The method delegates to GestureDetector.OnGestureListener

GestureBuilder

Lets create and save gestures

  • GestureLibraries load the gestures in runtime
  • GestureBuilder stores gestures in
    • /mnt/sdcard/gestures

To user it:
  • Include GestureOverlayView in the layout
    • Intercepts user gestures and invoke application code
  • Copy the file from  /mnt/sdcard/gestures to /res/draw directory










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