wetterApp/lib/components/locations/add_location_form.dart

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

class AddLocationsForm extends StatefulWidget {
  final SharedPreferences prefs;

  const AddLocationsForm(this.prefs, {Key? key}) : super(key: key);

  @override
  AddLocationsFormState createState() => AddLocationsFormState();
}

class AddLocationsFormState extends State<AddLocationsForm> {
  final _formKey = GlobalKey<FormState>();
  final locationFormController = TextEditingController();
  String? newLocationName;
  double? newLatitude;
  double? newLongitude;
  late List<String> savedLocations;

  @override
  void initState() {
    super.initState();
    savedLocations = widget.prefs.getStringList('savedLocations') ?? [];
  }

  @override
  void dispose() {
    locationFormController.dispose();
    super.dispose();
  }

  void _submitLocation() {
    if (_formKey.currentState!.validate()) {
      _formKey.currentState!.save();
      _saveLocationToPrefs(newLocationName!, newLatitude!, newLongitude!);
      _formKey.currentState!.reset();
      newLocationName = null;
      newLatitude = null;
      newLongitude = null;
    }
  }

  void _saveLocationToPrefs(String name, double lat, double lon) {
    savedLocations.add(name);
    widget.prefs.setStringList('savedLocations', savedLocations);
    widget.prefs.setDouble("$name-lat", lat);
    widget.prefs.setDouble("$name-lon", lon);
  }

  @override
  Widget build(BuildContext context) {
    return Form(
        key: _formKey,
        child: Column(children: [
          Flexible(
              flex: 4,
              child: TextFormField(
                //Location Name
                onSaved: (input) {
                  newLocationName = input;
                },
                controller: locationFormController,
                validator: ((value) {
                  if (value == null || value.isEmpty) {
                    return "Please enter a name for the new location";
                  }
                  if (savedLocations.contains(value)) {
                    return "Location name already in use";
                  }
                  return null;
                }),
                decoration: const InputDecoration(
                    border: UnderlineInputBorder(), labelText: "Location Name"),
              )),
          Row(
            crossAxisAlignment: CrossAxisAlignment.end,
            children: [
              Flexible(
                  flex: 1,
                  child: TextFormField(
                    //Latitude
                    validator: ((value) {
                      if (value == null || value.isEmpty) {
                        return "Please enter a value";
                      }
                      try {
                        double.parse(value);
                      } catch (e) {
                        return "Please enter a number";
                      }
                      return null;
                    }),
                    onSaved: (input) {
                      newLatitude = double.parse(input!);
                    },
                    keyboardType: TextInputType.number,
                    decoration: const InputDecoration(
                        border: UnderlineInputBorder(), labelText: "Latitude"),
                  )),
              const SizedBox(width: 10),
              Flexible(
                  flex: 1,
                  child: TextFormField(
                    //Longitude
                    validator: ((value) {
                      if (value == null || value.isEmpty) {
                        return "Please enter a value";
                      }
                      try {
                        double.parse(value);
                      } catch (e) {
                        return "Please enter a number";
                      }
                      return null;
                    }),
                    onSaved: (input) {
                      newLongitude = double.parse(input!);
                    },
                    keyboardType: TextInputType.number,
                    decoration: const InputDecoration(
                        border: UnderlineInputBorder(), labelText: "Longitude"),
                  )),
              const SizedBox(width: 10),
              Flexible(
                  flex: 2,
                  child: ElevatedButton(
                      onPressed: () {
                        _submitLocation();
                      },
                      child: Row(
                        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                        children: const [
                          Icon(Icons.add),
                          SizedBox(width: 5),
                          Text("Add Location")
                        ],
                      )))
            ],
          )
        ]));
  }
}