GestureDetector constructor

GestureDetector({Key key, Widget child, GestureTapDownCallback onTapDown, GestureTapUpCallback onTapUp, GestureTapCallback onTap, GestureTapCancelCallback onTapCancel, GestureTapCallback onDoubleTap, GestureLongPressCallback onLongPress, GestureLongPressUpCallback onLongPressUp, GestureDragDownCallback onVerticalDragDown, GestureDragStartCallback onVerticalDragStart, GestureDragUpdateCallback onVerticalDragUpdate, GestureDragEndCallback onVerticalDragEnd, GestureDragCancelCallback onVerticalDragCancel, GestureDragDownCallback onHorizontalDragDown, GestureDragStartCallback onHorizontalDragStart, GestureDragUpdateCallback onHorizontalDragUpdate, GestureDragEndCallback onHorizontalDragEnd, GestureDragCancelCallback onHorizontalDragCancel, GestureDragDownCallback onPanDown, GestureDragStartCallback onPanStart, GestureDragUpdateCallback onPanUpdate, GestureDragEndCallback onPanEnd, GestureDragCancelCallback onPanCancel, GestureScaleStartCallback onScaleStart, GestureScaleUpdateCallback onScaleUpdate, GestureScaleEndCallback onScaleEnd, HitTestBehavior behavior, bool excludeFromSemantics: false })

Creates a widget that detects gestures.

Pan and scale callbacks cannot be used simultaneously because scale is a superset of pan. Simply use the scale callbacks instead.

Horizontal and vertical drag callbacks cannot be used simultaneously because a combination of a horizontal and vertical drag is a pan. Simply use the pan callbacks instead.

By default, gesture detectors contribute semantic information to the tree that is used by assistive technology.

Implementation 

GestureDetector({
  Key key,
  this.child,
  this.onTapDown,
  this.onTapUp,
  this.onTap,
  this.onTapCancel,
  this.onDoubleTap,
  this.onLongPress,
  this.onLongPressUp,
  this.onVerticalDragDown,
  this.onVerticalDragStart,
  this.onVerticalDragUpdate,
  this.onVerticalDragEnd,
  this.onVerticalDragCancel,
  this.onHorizontalDragDown,
  this.onHorizontalDragStart,
  this.onHorizontalDragUpdate,
  this.onHorizontalDragEnd,
  this.onHorizontalDragCancel,
  this.onPanDown,
  this.onPanStart,
  this.onPanUpdate,
  this.onPanEnd,
  this.onPanCancel,
  this.onScaleStart,
  this.onScaleUpdate,
  this.onScaleEnd,
  this.behavior,
  this.excludeFromSemantics = false
}) : assert(excludeFromSemantics != null),
     assert(() {
       final bool haveVerticalDrag = onVerticalDragStart != null || onVerticalDragUpdate != null || onVerticalDragEnd != null;
       final bool haveHorizontalDrag = onHorizontalDragStart != null || onHorizontalDragUpdate != null || onHorizontalDragEnd != null;
       final bool havePan = onPanStart != null || onPanUpdate != null || onPanEnd != null;
       final bool haveScale = onScaleStart != null || onScaleUpdate != null || onScaleEnd != null;
       if (havePan || haveScale) {
         if (havePan && haveScale) {
           throw FlutterError(
             'Incorrect GestureDetector arguments.\n'
             'Having both a pan gesture recognizer and a scale gesture recognizer is redundant; scale is a superset of pan. Just use the scale gesture recognizer.'
           );
         }
         final String recognizer = havePan ? 'pan' : 'scale';
         if (haveVerticalDrag && haveHorizontalDrag) {
           throw FlutterError(
             'Incorrect GestureDetector arguments.\n'
             'Simultaneously having a vertical drag gesture recognizer, a horizontal drag gesture recognizer, and a $recognizer gesture recognizer '
             'will result in the $recognizer gesture recognizer being ignored, since the other two will catch all drags.'
           );
         }
       }
       return true;
     }()),
     super(key: key);