alto_great_circle_distance 0.0.3

Plugin for calculating Great Circle Distance with Spherical Law of Cosines.

example/lib/main.dart

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

import 'package:flutter/services.dart';
import 'package:alto_great_circle_distance/alto_great_circle_distance.dart';

void main() {
  runApp(const MyApp());
}

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

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  String _platformVersion = 'Unknown';

  // The distance
  double? _distance;

  @override
  void initState() {
    super.initState();
    initPlatformState();
    _calculate();
  }

  // Platform messages are asynchronous, so we initialize in an async method.
  Future<void> initPlatformState() async {
    String platformVersion;
    // Platform messages may fail, so we use a try/catch PlatformException.
    // We also handle the message potentially returning null.
    try {
      platformVersion = await GCD.platformVersion ?? 'Unknown platform version';
    } on PlatformException {
      platformVersion = 'Failed to get platform version.';
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;

    setState(() {
      _platformVersion = platformVersion;
    });
  }

  Future<void> _calculate() async {
    // The Geolocation of St.Mary Cathedral
    final Geo geo1 = Geo(lat: 16.77858116672366, lon: 96.1657684686045);
    // The Geolocation of St. Peter's Basilica
    final Geo geo2 = Geo(lat: 41.90219864557144, lon: 12.454035933187363);
    final double? _theDistance = await GCD().cal(geo1: geo1, geo2: geo2);
    setState(() => _distance = _theDistance);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Great Circle Distance'),
        ),
        body: SafeArea(
          child: Container(
            width: double.infinity,
            padding: const EdgeInsets.all(15),
            child: Column(
              children: [
                Text('Running on: $_platformVersion\n'),
                Text(
                    'The distance between St.Mary Cathedral, Myanmar and St.Peter\'s Basilica is ${_distance ?? "-"} km.'),
              ],
            ),
          ),
        ),
      ),
    );
  }
}