GestureDetector should take an onDoubleTapDown GestureTapDownCallback argument

[collinjackson]

This will allow clients of GestureRecognizer to determine the position of the double-tap, e.g. for double-tap-to-zoom.

Originally asked in http://stackoverflow.com/questions/43937841/how-do-i-get-tap-locations-gesturedetector

[collinjackson]

@abarth

[modulovalue]

Just wanted to give my +1.
Use case:
To let the user zoom in to a specific location on a canvas with a double tap
To let the user move the canvas by X to the left or right by double tapping on either side

Edit: this package works great for getting a position positioned_tap_detector

[csells]

You can use onTapDown to capture the position and then use it in your onDoubleTap handler.

[gschier]

@csells onTapDown does not get called when onDoubleTap is triggered.

[everoo]

The best cure I've found for this is keeping track of the previous point as pointA:

onTapDown: (pointB) {
if (pointA != Offset.zero &&
(pointB.globalPosition.dx - pointA.dx < 20 &&
pointB.globalPosition.dy - pointA.dy < 20)) {
print('double Tapped!');
} else {
pointA = pointB.globalPosition;
}
Timer(Duration(milliseconds: 500), () {
pointA = Offset.zero;
});
},