Save Favorites

In this guide you will learn how to save landmarks to your favorites list, as well as remove them from favorites.

Setup

First, get an API key token, see the Getting Started guide.

Prerequisites

It is required that you complete the Environment Setup - Flutter Examples guide before starting this guide.

Run the example

Start a terminal/command prompt and go to the save_favorites directory, within the flutter examples directory

Build and run the example:

Build and run

Note - the gem_kit directory containing the Maps SDK for Flutter should be in the plugins directory of the example, e.g. save_favorites/plugins/gem_kit - see the environment setup guide above.

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:

Web browser

flutter run

If such a question appears, select the chrome browser; in the above example, press 2.

Android

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:

allprojects {
    repositories {
        google()
        mavenCentral()
        maven {
           url "${rootDir}/../plugins/gem_kit/android/build"
        }
    }
}

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:

android {
    defaultConfig {
        applicationId "com.magiclane.gem_kit.examples.save_favorites"
        minSdk 21
        targetSdk flutter.targetSdk
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }
    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            minifyEnabled false
            shrinkResources false
            signingConfig signingConfigs.debug
        }
    }
}

Then build the apk:

flutter build apk --debug

or

flutter build apk --release

the apk file is located in the build/app/outputs/apk/debug or build/app/outputs/apk/release subdirectory, for debug or release build respectively, within the current project directory, which is save_favorites in this case.

The apk file name is app-release.apk or app-debug.apk

You can copy the apk to an android device using adb, for example:

adb push app-release.apk sdcard

And then click on the apk in the file browser on the device to install and run it.

iOS

In the ios/Podfile configuration text file, at the top, set the minimum ios platform to 13 like this:

platform :ios, '13.0'

Run pod install in the [ios folder] ./ios/

Then go back to the repository root folder and type flutter build ios to build a Runner.app.

Type flutter run to build and run on an attached device.

You can open the <path/to>/ios/Runner.xcworkspace project in Xcode and execute and debug from there.

How it works

In the save_favorites project directory, there is a text file named pubspec.yaml which contains project configuration and dependencies. The most important lines from this file are shown here:

name: simulate_route
version: 1.0.0+1

environment:
  sdk: '>=3.0.5 <4.0.0'

dependencies:
  flutter:
    sdk: flutter
  gem_kit:
    path: plugins/gem_kit

  cupertino_icons: ^1.0.2

# The following section is specific to Flutter packages.
flutter:
  uses-material-design: true

The project must have a name and version. The dependencies list the Flutter SDK, and the gem_kit, Maps for Flutter SDK.

The source code is in save_favorites/lib/main.dart

import 'dart:typed_data';

import 'package:flutter/material.dart';

import 'package:gem_kit/api/gem_coordinates.dart';
import 'package:gem_kit/api/gem_landmark.dart';
import 'package:gem_kit/api/gem_landmarkstore.dart';
import 'package:gem_kit/api/gem_landmarkstoreservice.dart';
import 'package:gem_kit/api/gem_mapviewrendersettings.dart';
import 'package:gem_kit/api/gem_routingservice.dart';
import 'package:gem_kit/api/gem_sdksettings.dart';
import 'package:gem_kit/gem_kit_map_controller.dart';
import 'package:gem_kit/widget/gem_kit_map.dart';

import 'favorites_page.dart';
import 'landmark_panel.dart';
import 'utility.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Save favorites example',
      home: MyHomePage(),
    );
  }
}

// Model class which contains information about the landmark
class PanelInfo {
  Uint8List? image;
  String name;
  String categoryName;
  String formattedCoords;

  PanelInfo(
    {this.image,
    required this.name,
    required this.categoryName,
    required this.formattedCoords});
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

The dart material package is imported, as well as the gem_kit packages for the map controller, which enables user input such as pan and zoom, the map package which draws the map, the landmark and coordinates packages for geolocation, the landmarkstore and landmarkstoreservice for favorites, and the settings and mapviewrendersettings packages.

The map is in a widget which is the root of the application.

class _MyHomePageState extends State<MyHomePage> {
  Landmark? _focusedLandmark;
  // GemMapController object used to interact with the map
  late GemMapController _mapController;

  // SdkSettings object to initialize the SDK
  late SdkSettings _sdkSettings;

  // LandmarkStoreServiceObject to get or create the LandmarkStore
  late LandmarkStoreService _landmarkStoreService;

  // LandmarkStore object to save Landmarks
  late LandmarkStore? _favoritesStore;

  late bool _isLandmarkFavorite;

  final favoritesStoreName = 'Favorites';

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

  Future<void> onMapCreated(GemMapController controller) async {
    _mapController = controller;
    _focusedLandmark = null;
    _isLandmarkFavorite = false;

    final token = 'YOUR_API_KEY_TOKEN';

    SdkSettings.create(_mapController.mapId).then((value) {
      _sdkSettings = value;
      _sdkSettings.setAppAuthorization(token);
    });

    // Instantiate the LandmarkStoreService.
    _landmarkStoreService = await LandmarkStoreService.create(controller.mapId);

    // Retrieves the LandmarkStore with the given name.
    _favoritesStore =
        await _landmarkStoreService.getLandmarkStoreByName(favoritesStoreName);

    // If there is no LandmarkStore with this name, then create it.
    _favoritesStore ??=
        await _landmarkStoreService.createLandmarkStore(favoritesStoreName);

    // Listen for map landmark selection events.
    _registerLandmarkTapCallback();
  }

The map is initialized with the map controller and the settings.

Setting the API key

The string "YOUR_API_KEY_TOKEN" should be replaced with your actual API key token string.

A tap on a landmark causes a panel to appear at the bottom, showing the name, coordinates, and an icon indicating the type of the landmark. If the heart icon on the right side is white inside, that means the landmark is not in the favorites list, and a tap on the heart will add it to the favorites. Conversely, if the heart icon is completely red inside, that means the landmark is in the favorites list. To remove it from the list, tap the heart icon, and when the heart icon becomes white inside, that means the landmark is no longer in the favorites list.

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      backgroundColor: Colors.deepPurple[900],
      title: const Text('Favourites'),
      actions: [
        IconButton(
            onPressed: () => _onFavouritesButtonPressed(context),
            icon: const Icon(Icons.favorite))
      ],
    ),
    body: Center(
      child: Stack(children: [
        GemMap(
          onMapCreated: onMapCreated,
        ),
        if (_focusedLandmark != null)
          Positioned(
            bottom: 30,
            left: 10,
            child: FutureBuilder<PanelInfo>(
                future: getInfo(),
                builder: (context, snapshot) {
                  if (!snapshot.hasData) {
                    return Container();
                  }
                  return LandmarkPanel(
                    onCancelTap: onCancelTap,
                    onFavoritesTap: onFavoritesTap,
                    isFavoriteLandmark: _isLandmarkFavorite,
                    coords: snapshot.data!.formattedCoords,
                    category: snapshot.data!.name,
                    img: snapshot.data!.image!,
                    name: snapshot.data!.name,
                  );
                }),
          )
      ]),
    ),
    resizeToAvoidBottomInset: false,
  );
}

The top purple panel with the white heart icon to go to the list of saved favorites.

Future<PanelInfo> getInfo() async {
  late Uint8List? iconFuture;
  late String nameFuture;
  late Coordinates coordsFuture;
  late String coordsFutureText;
  late List<LandmarkCategory> categoriesFuture;

  iconFuture = await _decodeLandmarkIcon(_focusedLandmark!);
  nameFuture = await _focusedLandmark!.getName();
  coordsFuture = await _focusedLandmark!.getCoordinates();
  coordsFutureText =
      "${coordsFuture.latitude.toString()}, ${coordsFuture.longitude.toString()}";
  categoriesFuture = await _focusedLandmark!.getCategories();

  return PanelInfo(
      image: iconFuture,
      name: nameFuture,
      categoryName:
          categoriesFuture.isNotEmpty ? categoriesFuture.first.name! : '',
      formattedCoords: coordsFutureText);
}

Future<Uint8List?> _decodeLandmarkIcon(Landmark landmark) async {
  final data = await landmark.getImage(100, 100);
  return decodeImageData(data);
}

This Future retrieves the information about the selected landmark, which will then be displayed in the LandmarkPanel.

_registerLandmarkTapCallback() {
  _mapController.registerTouchCallback((pos) async {
    // Select the object at the tap position.
    await _mapController.selectMapObjects(pos);

    // Get the selected landmarks.
    final landmarks = await _mapController.cursorSelectionLandmarks();

    final landmarksSize = await landmarks.size();

    // Check if there is a selected Landmark.
    if (landmarksSize == 0) return;

    // Highlight the landmark on the map.
    _mapController.activateHighlight(landmarks);

    final lmk = await landmarks.at(0);
    setState(() {
      _focusedLandmark = lmk;
    });

    await _checkIfFavourite();
  });
}

If the user tapped on the map, check if there are any landmarks at that location. If there are, grab the first one (at index 0) and check if it is already in the list of favorites.

_onFavouritesButtonPressed(BuildContext context) async {
  // Fetch landmarks from the store
  final favoritesList = await _favoritesStore!.getLandmarks();

  // Navigating to favorites screen then the result will be the selected item in the list.
  final result = await Navigator.of(context).push(MaterialPageRoute(
    builder: (context) => FavoritesPage(landmarkList: favoritesList),
  ));

  // Create a list of landmarks to highlight.
  LandmarkList landmarkList = await LandmarkList.create(_mapController.mapId);

  if (result is! Landmark) {
    return;
  }

  // Add the result to the landmark list.
  await landmarkList.push_back(result);
  final coords = await result.getCoordinates();

  // Highlight the landmark on the map.
  await _mapController.activateHighlight(landmarkList,
      renderSettings: RenderSettings());

  // Centering the camera on landmark's coordinates
  await _mapController.centerOnCoordinates(coords);

  setState(() {
    _focusedLandmark = result;
  });
  await _checkIfFavourite();
}

The method to navigate to the favorites list page.

void onCancelTap() {
  // Remove landmark highlights from the map
  _mapController.deactivateAllHighlights();

  setState(() {
    _focusedLandmark = null;
    _isLandmarkFavorite = false;
  });
}

void onFavoritesTap() async {
  await _checkIfFavourite();

  if (_isLandmarkFavorite) {
    // Remove the landmark to the store.
    await _favoritesStore!.removeLandmark(_focusedLandmark!);
  } else {
    // Add the landmark to the store.
    await _favoritesStore!.addLandmark(_focusedLandmark!);
  }
  setState(() {
    _isLandmarkFavorite = !_isLandmarkFavorite;
  });
}

Once the landmark info panel is displayed at the bottom, about the selected landmark, the heart icon is either white inside, and a tap on it adds the landmark to the favorites, or the heart icon is red inside, and a tap on it removes the landmark from the favorites.

A tap on the heart icon at the top right shows the list of favorites.

_checkIfFavourite() async {
  final focusedLandmarkCoords = await _focusedLandmark!.getCoordinates();
  final favourites = await _favoritesStore!.getLandmarks();
  final favoritesSize = await favourites.size();

  for (int i = 0; i < favoritesSize; i++) {
    final lmk = await favourites.at(i);
    final coords = await lmk.getCoordinates();

    if (focusedLandmarkCoords.latitude == coords.latitude &&
        focusedLandmarkCoords.longitude == coords.longitude) {
      setState(() {
        _isLandmarkFavorite = true;
      });
      return;
    }
  }

  setState(() {
    _isLandmarkFavorite = false;
  });
}
}

A method to check if the highlighted landmark is in the favorites list.