initState

()

super

initState

();

recognizer

PanGestureRecognizer

()

onStart

_onPanStart

onUpdate

_onPanUpdate

onEnd

_onPanEnd

void

_onPanStart

DragStartDetails

details

debugPrint

'onStart'

);

void

_onPanUpdate

DragUpdateDetails

details

debugPrint

'onUpdate'

);

void

_onPanEnd

DragEndDetails

details

debugPrint

'onEnd'

);