positioned-tap-detector

Flutter widget allowing to receive tap callbacks, together with their position on the screen. It supports onTap, onDoubleTap and onLongPress gestures. Each callback function is invoked with TapPosition object that provides global and relative touch position. To adjust maximum time allowed between double-tap gesture consecutive taps, specify an additional doubleTapDelay parameter:

PositionedTapDetector(
  onTap: (position) => _printTap('Single tap', position),
  onDoubleTap: (position) => _printTap('Double tap', position),
  onLongPress: (position) => _printTap('Long press', position),
  doubleTapDelay: Duration(milliseconds: 500),
  child: ...,
)

void _printTap(String gesture, TapPosition position) => 
    print('$gesture: ${position.global}, ${position.relative}');

Controller

In case you need to wrap another GestureDetector below in the widget tree, pass an additional PositionedTapController parameter and invoke its callback methods whenever relevant gesture takes place:

final _controller = PositionedTapController();

Widget build(BuildContext context) {
  // ...
    child: PositionedTapDetector(
      // ...
      controller: _controller,
      child: GestureDetector(
        onTap: _handleTap,
        onTapDown: _controller.onTapDown,
        onLongPress: _controller.onLongPress,
        behavior: ...,
        child: ...,
      ),
    ),
}

void _handleTap() {
  // ...
  _controller.onTap();
}

Drawbacks

PositionedTapDetector will not invoke onDoubleTap callback in case there's GestureDetector underneath it in the widget tree that also specifies onDoubleTap parameter. Since Flutter framework doesn't invoke its onTapDown callback when detector is double-tapped, positioned detector is unable to receive tap positions and therefore detect double-tap gestures.