Question 75640 in Flutter Question posted in
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How do I pass an optional parameter from one stateful screen to another? – Flutter

I have a HomePage, from where I want to pass my coordinates:

child: FloatingActionButton(
 onPressed: () {
  Navigator.push(
   context,
   MaterialPageRoute(builder: (context) => MapScreen(historyItem.latLong)),
    );
   },
   child: Icon(Icons.place),
)

I want to pass them to my MapScreen, which is stateful. However, I want these coordinates to be an optional argument with initial values so that I can decide the behavior of MapScreen depending on my arguments passed:

class MapScreen extends StatefulWidget {
  const MapScreen({Key? key}) : super(key: key);

  final AppLatLong kPoint = const AppLatLong(lat: 0, long: 0);

  @override
  State<MapScreen> createState() => _MapScreenState();
}

How do I do that? Is it possible?

Thanks everyone in advance!

Tags:

2

Answers


  1. 0

    make this Mapscreen constructor like this:

    MapScreen({super.key, this.lat = 0, this.long = 0});

double lat;
double long;

    and pass the parameter like this:

    child: FloatingActionButton(
onPressed: () {
Navigator.push(
 context,
MaterialPageRoute(builder: (context) => MapScreen(lat:historyItem.lat,long:historyItem.long)),
);
},
child: Icon(Icons.place),
)

    let me know if this is working for you.

    Login or Signup to reply.
  2. 0 
    class MapScreen extends StatefulWidget {
    const MapScreen({
         this.kPoint = const AppLatLong(lat: 0, long: 0),
         Key? key,
    }) : super(key: key);

    final AppLatLong kPoint;

    @override
  State<MapScreen> createState() => _MapScreenState();
}

    Now your kPoint is optional, if you pass a kPoint you will have this, if not, you have your default value const AppLatLong(lat: 0, long: 0).
    My example is a named param, so you would’ve to use like this

     MaterialPageRoute(builder: (context) => MapScreen(kPoint: historyItem.latLong)),

    But if you want a positioned param, declare the param outside the curly braces:

    class MapScreen extends StatefulWidget {
    const MapScreen(
        this.kPoint = const AppLatLong(lat: 0, long: 0),
        { Key? key }
    ) : super(key: key);

    final AppLatLong kPoint;

    @override
    State<MapScreen> createState() => _MapScreenState();
}

    …

    MaterialPageRoute(builder: (context) => MapScreen(historyItem.latLong)),
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