Call a void function from another file - flutter

Question

I'm creating an app that has a start button (class StartButton) and i want that button calls a method from another class (class NewRide), but how can i call a void function from another file?
class StartButton extends StatefulWidget{
#override
_StartButtonState createState() => _StartButtonState();
}
class _StartButtonState extends State<StartButton> {
String _driverState = 'offline';
#override
Widget build(context){
return FlatButton(
child: Text('Start'),
onPressed: (){
setState(() {
if (_driverState == 'offline') {
_driverState = 'online';
} else {
_driverState = 'offline';
}
});
},
);
}
}
This is New Ride class, it has the void function i want to call when i press start button.
class NewRide extends StatefulWidget {
#override
_NewRideState createState() => _NewRideState();
}
class _NewRideState extends State<NewRide> {
int _counter = 60;
Timer _timer;
#override
Widget build(BuildContext context) {
void startTimer() {
_counter = 60;
if (_timer != null) {
_timer.cancel();
}
_timer = Timer.periodic(Duration(seconds: 1), (timer) {
setState(() {
if (_counter > 0) {
_counter--;
} else {
_timer.cancel();
}
});
});
}
_showNewRideAlert() {
if (_counter == 0) {
return Text('Counter == 0');
} else {
return Text('Counter != 0');
}
}
return _showNewRideAlert();
}
}

Answer 1

use GlobalKey and make startTimer public and change NewRideState to _ NewRideState
class StartButton extends StatefulWidget {
#override
_StartButtonState createState() => _StartButtonState();
}
class _StartButtonState extends State<StartButton> {
String _driverState = 'offline';
GlobalKey<NewRideState> newRideKey = GlobalKey<NewRideState>();
#override
Widget build(context) {
return Column(
children: [
NewRide(key: newRideKey),
FlatButton(
child: Text('Start'),
onPressed: () {
setState(() {
if (_driverState == 'offline') {
_driverState = 'online';
} else {
_driverState = 'offline';
}
});
},
),
],
);
}
}
class NewRide extends StatefulWidget {
const NewRide({Key key}) : super(key: key);
#override
NewRideState createState() => NewRideState();
}
class NewRideState extends State<NewRide> {
int _counter = 60;
Timer _timer;
#override
Widget build(BuildContext context) {
_showNewRideAlert() {
if (_counter == 0) {
return Text('Counter == 0');
} else {
return Text('Counter != 0');
}
}
return _showNewRideAlert();
}
void startTimer() {
_counter = 60;
if (_timer != null) {
_timer.cancel();
}
_timer = Timer.periodic(Duration(seconds: 1), (timer) {
setState(() {
if (_counter > 0) {
_counter--;
} else {
_timer.cancel();
}
});
});
}
}

Answer 2

First import the other file/class into the main class (I'm not sure what your file is called).
import '.../newRide.dart' as newRide;
Then call the function like this:
newRide._showNewRideAlert();
It might not work due to how the class/state is setup though (the widget won't be built). So you may have to move the code into a place that is callable, such as the top of the class or implement the function into the page where it is used.