onStart property Null safety
read / write
A pointer is in contact with the screen and has just pressed with a force exceeding the startPressure. Consequently, if there were other gesture detectors, only the force press gesture will be detected and all others will be rejected.
The position of the pointer is provided in the callback's details
argument, which is a ForcePressDetails object.
Implementation
GestureForcePressStartCallback? onStart;