onSerialTapDown property
getter/setter pair
A pointer has contacted the screen at a particular location, which might be the start of a serial tap.
If this recognizer loses the arena before the serial tap is completed (either because the gesture does not end up being a tap or because another recognizer wins the arena), onSerialTapCancel is called next. Otherwise, onSerialTapUp is called next.
The SerialTapDownDetails.count that is passed to this callback specifies the series tap count.
Implementation
GestureSerialTapDownCallback? onSerialTapDown;