onLongPressEnd property Null safety
A pointer that has triggered a long-press with a primary button has stopped contacting the screen.
This is equivalent to (and is called immediately before) onLongPressUp. The only difference between the two is that this callback contains details of the state of the pointer when it stopped contacting the screen, whereas onLongPressUp does not.
final GestureLongPressEndCallback? onLongPressEnd;