Flutter地理位置计算插件calc_lat_long的使用

Flutter地理位置计算插件calc_lat_long的使用

calc_lat_long 是一个用于计算两个地理坐标点（纬度和经度）之间的距离的包。它可以按英里、公里或海里来计算距离。

开始使用

1. 在 pubspec.yaml 文件中添加最新版本的插件，并运行 dart pub get 命令：

   dependencies:
     calc_lat_long: ^1.0.12
   

示例代码

以下是一个完整的示例代码，展示了如何使用 calc_lat_long 插件来计算两个地理坐标点之间的距离。

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

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

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: '计算两个点的距离'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  [@override](/user/override)
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final TextEditingController latitude1 = TextEditingController();
  final TextEditingController latitude2 = TextEditingController();
  final TextEditingController longitude1 = TextEditingController();
  final TextEditingController longitude2 = TextEditingController();

  var distance = 0.0;
  var _unitLength = [UnitLength.km, UnitLength.mi, UnitLength.nm];
  UnitLength _selectedUnit = UnitLength.km;

  void _dropDownItemSelected(UnitLength novoItem) {
    setState(() {
      _selectedUnit = novoItem;
    });
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Padding(
        padding: EdgeInsets.all(16),
        child: ListView(
          keyboardDismissBehavior: ScrollViewKeyboardDismissBehavior.onDrag,
          children: <Widget>[
            TextField(
              controller: latitude1,
              decoration: InputDecoration(labelText: "纬度 1"),
            ),
            TextField(
              controller: longitude1,
              decoration: InputDecoration(labelText: "经度 1"),
            ),
            TextField(
              controller: latitude2,
              decoration: InputDecoration(labelText: "纬度 2"),
            ),
            TextField(
              controller: longitude2,
              decoration: InputDecoration(labelText: "经度 2"),
            ),
            DropdownButton<UnitLength>(
                items: _unitLength.map((UnitLength dropDownStringItem) {
                  return DropdownMenuItem<UnitLength>(
                    value: dropDownStringItem,
                    child: Text(dropDownStringItem.toString()),
                  );
                }).toList(),
                onChanged: (UnitLength? newUnitSelected) {
                  _dropDownItemSelected(newUnitSelected!);
                  setState(() {
                    _selectedUnit = newUnitSelected;
                  });
                },
                value: _selectedUnit),
            SizedBox(
              height: 15,
            ),
            ElevatedButton(
                onPressed: () {
                  var dist = CalcDistance.distance(
                      double.parse(latitude1.text),
                      double.parse(latitude2.text),
                      double.parse(longitude1.text),
                      double.parse(longitude2.text),
                      _selectedUnit);

                  setState(() {
                    distance = dist;
                  });
                },
                child: Text("计算")),
            SizedBox(
              height: 15,
            ),
            Text(distance == 0 ? "" : "距离: $distance")
          ],
        ),
      )
    );
  }
}