onSingleLongTapStart property Null safety

GestureLongPressStartCallback? onSingleLongTapStart
final

Called for a single long tap that's sustained for longer than kLongPressTimeout but not necessarily lifted. Not called for a double-tap-hold, which calls onDoubleTapDown instead.

Implementation

final GestureLongPressStartCallback? onSingleLongTapStart;