Follow Position¶
Setup¶
Prerequisites¶
Build and Run¶
Navigate to the follow_position
directory within the Flutter examples directory. This is the project folder for this example.
Note - the gem_kit
directory containing the Maps SDK for Flutter
should be in the plugins
directory of the example, e.g.
example_pathname/plugins/gem_kit
- see the environment setup guide above.
Replace example_pathname
with the actual example path name,
such as address_search
Download project dependencies:
flutter upgrade
run the following terminal commands in the project directory,
where the pubspec.yaml
file is located:
flutter clean
flutter pub get
Run the example:
First, verify that the ANDROID_SDK_ROOT
environment variable
is set to the root path of your android SDK.
In android/build.gradle
add the maven {}
block as shown,
within the allprojects {} block
, for both debug and release builds,
without the line numbers, those are for reference:
1allprojects {
2 repositories {
3 google()
4 mavenCentral()
5 maven {
6 url "${rootDir}/../plugins/gem_kit/android/build"
7 }
8 }
9}
in android/app/build.gradle
within the android {}
block, in the defaultConfig {}
block,
the android SDK version minSdk
must be set as shown below.
Additionally, for release builds, in android/app/build.gradle
,
within the android {}
block, add the buildTypes {}
block as shown:
Replace example_pathname
with the actual example pathname, such as center_coordinates
1android {
2 defaultConfig {
3 applicationId "com.magiclane.gem_kit.examples.example_pathname"
4 minSdk 21
5 targetSdk flutter.targetSdk
6 versionCode flutterVersionCode.toInteger()
7 versionName flutterVersionName
8 }
9 buildTypes {
10 release {
11 minifyEnabled false
12 shrinkResources false
13
14 // TODO: Add your own signing config for the release build.
15 // Signing with the debug keys for now, so `flutter run --release` works.
16 signingConfig signingConfigs.debug
17 }
18 }
19}
Then run the project:
flutter run --debug
flutter run --release
In the ios/Podfile
configuration text file, at the top, set the minimum ios
platform to 13 like this:
platform :ios, '13.0'
Then run the project:
flutter run --debug
flutter run --release
How It Works¶
The example app demonstrates the following features:
Requesting location permissions on Android and iOS, with automatic handling on web platforms.
Setting the live data source for the map (typically the device’s GPS).
Following the device’s location on the map with optional animation.
1import 'package:gem_kit/core.dart';
2import 'package:gem_kit/map.dart';
3import 'package:gem_kit/sense.dart';
4
5import 'package:permission_handler/permission_handler.dart';
6
7import 'package:flutter/foundation.dart';
8import 'package:flutter/material.dart' hide Animation;
9
10Future<void> main() async {
11 const projectApiToken = String.fromEnvironment('GEM_TOKEN');
12
13 await GemKit.initialize(appAuthorization: projectApiToken);
14
15 runApp(const MyApp());
16}
This code initializes the GemKit SDK with the necessary authorization and sets up the main entry point of the app.
UI and Map Integration¶
1class MyApp extends StatelessWidget {
2 const MyApp({super.key});
3
4 @override
5 Widget build(BuildContext context) {
6 return const MaterialApp(
7 debugShowCheckedModeBanner: false,
8 title: 'Follow Position',
9 home: MyHomePage(),
10 );
11 }
12}
13
14class MyHomePage extends StatefulWidget {
15 const MyHomePage({super.key});
16
17 @override
18 State<MyHomePage> createState() => _MyHomePageState();
19}
20
21class _MyHomePageState extends State<MyHomePage> {
22 late GemMapController _mapController;
23
24 PermissionStatus _locationPermissionStatus = PermissionStatus.denied;
25 bool _hasLiveDataSource = false;
26
27 @override
28 void dispose() {
29 GemKit.release();
30 super.dispose();
31 }
32
33 @override
34 Widget build(BuildContext context) {
35 return Scaffold(
36 appBar: AppBar(
37 backgroundColor: Colors.deepPurple[900],
38 title: const Text('Follow Position', style: TextStyle(color: Colors.white)),
39 actions: [
40 IconButton(
41 onPressed: _onFollowPositionButtonPressed,
42 icon: const Icon(Icons.location_searching_sharp, color: Colors.white),
43 ),
44 ],
45 ),
46 body: GemMap(
47 onMapCreated: _onMapCreated,
48 ),
49 );
50 }
This code sets up the app’s user interface, including a map and a button to follow the device’s position.
Handling Location Permissions and Following Position¶
1// The callback for when the map is ready to use.
2void _onMapCreated(GemMapController controller) async {
3 // Save controller for further usage.
4 _mapController = controller;
5}
6
7void _onFollowPositionButtonPressed() async {
8 if (kIsWeb) {
9 // On web platforms, permissions are handled differently.
10 _locationPermissionStatus = PermissionStatus.granted;
11 } else {
12 // Request location permission on Android and iOS platforms.
13 _locationPermissionStatus = await Permission.locationWhenInUse.request();
14 }
15
16 if (_locationPermissionStatus == PermissionStatus.granted) {
17 // Set the live data source (GPS) if not already set.
18 if (!_hasLiveDataSource) {
19 PositionService.instance.setLiveDataSource();
20 _hasLiveDataSource = true;
21 }
22
23 // Optionally, set an animation.
24 final animation = GemAnimation(type: AnimationType.linear);
25
26 // Start following the device's position.
27 _mapController.startFollowingPosition(animation: animation);
28
29 setState(() {});
30 }
31}
This code handles the process of requesting location permissions, setting the GPS as the live data source, and starting the map’s follow position mode.
Displaying Position Information¶
_onFollowPositionButtonPressed()
callback is triggered. It requests location permission if it hasn’t been granted already, and sets the location data source to the device’s GPS sensor.