onTapDown method
Implementation
GestureDetector onTapDown(ValueChanged<dynamic> onTapDown) => GestureDetector(
child: this,
onTapDown: onTapDown,
);
GestureDetector onTapDown(ValueChanged<dynamic> onTapDown) => GestureDetector(
child: this,
onTapDown: onTapDown,
);