BaseTapAndDragGestureRecognizer class sealed

A base class for gesture recognizers that recognize taps and movements.

Takes on the responsibilities of TapGestureRecognizer and DragGestureRecognizer in one GestureRecognizer.

Gesture arena behavior

BaseTapAndDragGestureRecognizer competes on the pointer events of kPrimaryButton only when it has at least one non-null onTap* or onDrag* callback.

It will declare defeat if it determines that a gesture is not a tap (e.g. if the pointer is dragged too far while it's contacting the screen) or a drag (e.g. if the pointer was not dragged far enough to be considered a drag.

This recognizer will not immediately declare victory for every tap that it recognizes, but it declares victory for every drag.

The recognizer will declare victory when all other recognizer's in the arena have lost, if the timer of kPressTimeout elapses and a tap series greater than 1 is being tracked, or until the pointer has moved a sufficient global distance from the origin to be considered a drag.

If this recognizer loses the arena (either by declaring defeat or by another recognizer declaring victory) while the pointer is contacting the screen, it will fire onCancel instead of onTapUp or onDragEnd.

When competing with TapGestureRecognizer and DragGestureRecognizer

Similar to TapGestureRecognizer and DragGestureRecognizer, BaseTapAndDragGestureRecognizer will not aggressively declare victory when it detects a tap, so when it is competing with those gesture recognizers and others it has a chance of losing. Similarly, when eagerVictoryOnDrag is set to false, this recognizer will not aggressively declare victory when it detects a drag. By default, eagerVictoryOnDrag is set to true, so this recognizer will aggressively declare victory when it detects a drag.

When competing against TapGestureRecognizer, if the pointer does not move past the tap tolerance, then the recognizer that entered the arena first will win. In this case the gesture detected is a tap. If the pointer does travel past the tap tolerance then this recognizer will be declared winner by default. The gesture detected in this case is a drag.

When competing against DragGestureRecognizer, if the pointer does not move a sufficient global distance to be considered a drag, the recognizers will tie in the arena. If the pointer does travel enough distance then the recognizer that entered the arena first will win. The gesture detected in this case is a drag.

RawGestureDetector(
  gestures: <Type, GestureRecognizerFactory>{
    TapAndPanGestureRecognizer: GestureRecognizerFactoryWithHandlers<TapAndPanGestureRecognizer>(
      () => TapAndPanGestureRecognizer(),
      (TapAndPanGestureRecognizer instance) {
        instance
          ..onTapDown = (TapDragDownDetails details) { setState(() { _last = 'down_a'; }); }
          ..onDragStart = (TapDragStartDetails details) { setState(() { _last = 'drag_start_a'; }); }
          ..onDragUpdate = (TapDragUpdateDetails details) { setState(() { _last = 'drag_update_a'; }); }
          ..onDragEnd = (TapDragEndDetails details) { setState(() { _last = 'drag_end_a'; }); }
          ..onTapUp = (TapDragUpDetails details) { setState(() { _last = 'up_a'; }); }
          ..onCancel = () { setState(() { _last = 'cancel_a'; }); };
      },
    ),
  },
  child: Container(
    width: 300.0,
    height: 300.0,
    color: Colors.yellow,
    alignment: Alignment.center,
    child: RawGestureDetector(
      gestures: <Type, GestureRecognizerFactory>{
        TapAndPanGestureRecognizer: GestureRecognizerFactoryWithHandlers<TapAndPanGestureRecognizer>(
          () => TapAndPanGestureRecognizer(),
          (TapAndPanGestureRecognizer instance) {
            instance
              ..onTapDown = (TapDragDownDetails details) { setState(() { _last = 'down_b'; }); }
              ..onDragStart = (TapDragStartDetails details) { setState(() { _last = 'drag_start_b'; }); }
              ..onDragUpdate = (TapDragUpdateDetails details) { setState(() { _last = 'drag_update_b'; }); }
              ..onDragEnd = (TapDragEndDetails details) { setState(() { _last = 'drag_end_b'; }); }
              ..onTapUp = (TapDragUpDetails details) { setState(() { _last = 'up_b'; }); }
              ..onCancel = () { setState(() { _last = 'cancel_b'; }); };
          },
        ),
      },
      child: Container(
        width: 150.0,
        height: 150.0,
        color: Colors.blue,
        child: Text(_last),
      ),
    ),
  ),
)