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How To Get a User's Location with the Geolocator Plugin in Flutter

 3 years ago
source link: https://www.digitalocean.com/community/tutorials/flutter-geolocator-plugin
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Introduction

Geolocation is the process of identifying a user’s current physical location when they are interacting with your application.

There is a geolocator package and a geocoding package for Flutter that can be used for geolocation.

In this article, you will create an example Flutter app that uses the geolocator and geocoding packages to determine the location of a user.

Prerequisites

To complete this tutorial, you will need:

  • To download and install Flutter.
  • To download and install Android Studio.

  • flutter doctor will also recommend:

    • Flutter and Dart plugins installed for Android Studio.
    • Flutter extension installed for Visual Studio Code.

Note: On macOS, it is also possible to use Homebrew to install Flutter and Android Studio:

brew install flutter brew cask install android-studio  

When installing Android Studio on macOS, you may need to allow system software from “Intel Corporation Apps” and agree to Android licenses.

This tutorial was verified with Flutter v1.22.2, Android SDK v30.0.2, and Android Studio v4.1. The code in this tutorial has been updated to support geolocator 6+ and geocoding 1+.

Step 1 — Setting Up the Project

Once you have your environment set up for Flutter, you can run the following to create a new application:

flutter create flutter_geolocator_example  

Navigate to the new project directory:

cd flutter_geolocator_example  

Using flutter create will produce a demo application that will display the amount of times a button is clicked.

Open pubspec.yaml in your code editor and add the following plugins:

pubspec.yaml
dependencies:
  flutter:
    sdk: flutter

  geocoding: ^1.0.5
  geolocator: ^6.1.1
 

Note: You will need to make sure that your Android project uses AndroidX for this. If you have created a Flutter application after version 1.7, this comes by default. If not, follow this guide: AndroidX Migration.

You will then need to add permissions to both Android and iOS by editing ios/Runner/Info.plist and android/app/src/main/AndroidManifest.xml.

iOS Permissions

Open Info.plist in your code editor and add NSLocationWhenInUseUsageDescription, NSLocationAlwaysUsageDescription, and NSLocationAlwaysAndWhenInUseUsageDescription:

Starting with iOS and the Info.plist, add the following key/value pairs and customize them to your liking:

ios/Runner/Info.plist
<key>NSLocationWhenInUseUsageDescription</key>
<string>This app needs access to location when open.</string>

<key>NSLocationAlwaysUsageDescription</key>
<string>This app needs access to location when in the background.</string>

<key>NSLocationAlwaysAndWhenInUseUsageDescription</key>
<string>This app needs access to location when open and in the background.</string>
 

If you do not intend to support iOS applications older than iOS 10 and you do not want to get user location when the application is not in use, you can forego the addition of NSLocationAlwaysUsageDescription and NSLocationAlwaysAndWhenInUseUsageDescription.

Android Permissions

Open AndroidManifest.xml in your code editor and add one of the following.

ACCESS_FINE_LOCATION:

android/app/src/main/AndroidManifest.xml
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
 

Or ACCESS_COARSE_LOCATION:

android/app/src/main/AndroidManifest.xml
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
 

ACCESS_FINE_LOCATION is the most precise, whereas ACCESS_COARSE_LOCATION gives results equal to about a city block.

With this setup complete, you can create the widget that will trigger and display the user’s current location.

Step 2 — Scaffolding the Project

Next, you will need to update the main.dart file and create a new home_page.dart file.

Open main.dart in your code editor and import home_page.dart and change the home from MyHomePage to HomePage:

lib/main.dart
import 'package:flutter/material.dart';
import 'home_page.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: HomePage(),
    );
  }
}
 

Then, create a new home_page.dart file and add the following code:

lib/home_page.dart
import 'package:flutter/material.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Location"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            FlatButton(
              child: Text("Get location"),
              onPressed: () {
                // Get location here
              },
            ),
          ],
        ),
      ),
    );
  }
}
 

This will create a button with the message "Get location".

Step 3 — Getting the Latitude and Longitude

The next step is adding the geolocation functionality.

You can accomplish that by creating an instance of Geolocator and calling getCurrentPosition. This should ask the user whether they are interested in using the Location feature, and if so, get the current location as a Position.

Revisit home_page.dart and add _getCurrentLocation():

lib/home_page.dart
import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  Position _currentPosition;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Location"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            if (_currentPosition != null) Text(
              "LAT: ${_currentPosition.latitude}, LNG: ${_currentPosition.longitude}"
            ),
            FlatButton(
              child: Text("Get location"),
              onPressed: () {
                _getCurrentLocation();
              },
            ),
          ],
        ),
      ),
    );
  }

  _getCurrentLocation() {
    Geolocator
      .getCurrentPosition(desiredAccuracy: LocationAccuracy.best, forceAndroidLocationManager: true)
      .then((Position position) {
        setState(() {
          _currentPosition = position;
        });
      }).catchError((e) {
        print(e);
      });
  }
}
 

Compile your code and have it run in an emulator:

Two screenshots of the application running in an emulator. The first screenshot depicts a prompt for allowing the app the access location. The second screenshot depicts a latitude and longitude for the location of the user.

When you interact with the Get location button, you may initially see a prompt requesting access to your app. Once you allow access to your location, the latitude and longitude of your current location will appear on screen.

Step 4 — Converting Latitude and Longitude to a Human-readable Address

The next step is converting the coordinates to display an address.

Passing latitude and longitude coordinates to placemarkFromCoordinates will return a Placemark. Placemark contains information like locality, postalCode, and country.

Revisit home_page.dart and add _getAddressFromLatLng_():

lib/home_page.dart
import 'package:flutter/material.dart';
import 'package:geocoding/geocoding.dart';
import 'package:geolocator/geolocator.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  Position _currentPosition;
  String _currentAddress;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Location"),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            if (_currentAddress != null) Text(
              _currentAddress
            ),
            FlatButton(
              child: Text("Get location"),
              onPressed: () {
                _getCurrentLocation();
              },
            ),
          ],
        ),
      ),
    );
  }

  _getCurrentLocation() {
    Geolocator
      .getCurrentPosition(desiredAccuracy: LocationAccuracy.best, forceAndroidLocationManager: true)
      .then((Position position) {
        setState(() {
          _currentPosition = position;
          _getAddressFromLatLng();
        });
      }).catchError((e) {
        print(e);
      });
  }

  _getAddressFromLatLng() async {
    try {
      List<Placemark> placemarks = await placemarkFromCoordinates(
        _currentPosition.latitude,
        _currentPosition.longitude
      );

      Placemark place = placemarks[0];

      setState(() {
        _currentAddress = "${place.locality}, ${place.postalCode}, ${place.country}";
      });
    } catch (e) {
      print(e);
    }
  }
}
 

Compile your code and have it run in an emulator:

Screenshot of the application running in an emulator with an address of San Francisco, 94108, United States displayed.

When you interact with the Get location button, you may initially see a prompt requesting access to your app. Once you allow access to your location, your locality, postalCode, and county will be displayed on the screen.

Conclusion

In this tutorial, you used geolocator and geocoding packages in a Flutter application.

If you’d like to learn more about Flutter, check out our Flutter topic page for exercises and programming projects.


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