Flutter Foreground Task

https://pub.dev/packages/flutter_foreground_task
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### Manage Service Lifecycle

Source: https://pub.dev/packages/flutter_foreground_task/example

Handles starting and stopping the foreground service, including checking if the service is already running.

```dart
  Future<ServiceRequestResult> _startService() async {
    if (await FlutterForegroundTask.isRunningService) {
      return FlutterForegroundTask.restartService();
    } else {
      return FlutterForegroundTask.startService(
        // You can manually specify the foregroundServiceType for the service
        // to be started, as shown in the comment below.
        // serviceTypes: [
        //   ForegroundServiceTypes.dataSync,
        //   ForegroundServiceTypes.remoteMessaging,
        // ],
        serviceId: 256,
        notificationTitle: 'Foreground Service is running',
        notificationText: 'Tap to return to the app',
        notificationIcon: null,
        notificationButtons: [
          const NotificationButton(id: 'btn_hello', text: 'hello'),
        ],
        notificationInitialRoute: '/second',
        callback: startCallback,
      );
    }
  }

  Future<ServiceRequestResult> _stopService() {
    return FlutterForegroundTask.stopService();
  }
```

--------------------------------

### Start Foreground Service

Source: https://pub.dev/packages/flutter_foreground_task

Starts or restarts the foreground service with specific notification settings and a task callback.

```dart
Future<ServiceRequestResult> _startService() async {
  if (await FlutterForegroundTask.isRunningService) {
    return FlutterForegroundTask.restartService();
  } else {
    return FlutterForegroundTask.startService(
      // You can manually specify the foregroundServiceType for the service
      // to be started, as shown in the comment below.
      // serviceTypes: [
      //   ForegroundServiceTypes.dataSync,
      //   ForegroundServiceTypes.remoteMessaging,
      // ],
      serviceId: 256,
      notificationTitle: 'Foreground Service is running',
      notificationText: 'Tap to return to the app',
      notificationIcon: null,
      notificationButtons: [
        const NotificationButton(id: 'btn_hello', text: 'hello'),
      ],
      notificationInitialRoute: '/',
      callback: startCallback,
    );
  }
}
```

--------------------------------

### Deprecated Color Property Usage

Source: https://pub.dev/packages/flutter_foreground_task/score

Example of a deprecated color property access identified during static analysis. Use the recommended color calculation formula instead.

```dart
  ╷
4 │   String get toRgbString => '$red,$green,$blue';
  │                               ^^^
  ╵
```

--------------------------------

### Deprecated WillPopScope Usage

Source: https://pub.dev/packages/flutter_foreground_task/score

Example of a deprecated WillPopScope usage identified during static analysis. Replace with PopScope to support Android predictive back navigation.

```dart
   ╷
31 │       WillPopScope(onWillPop: _onWillPop, child: widget.child);
   │       ^^^^^^^^^^^^
   ╵
```

--------------------------------

### Initialize Foreground Service and Permissions

Source: https://pub.dev/packages/flutter_foreground_task

Handles notification permissions, battery optimization settings, and service initialization configuration.

```dart
Future<void> _requestPermissions() async {
  // Android 13+, you need to allow notification permission to display foreground service notification.
  //
  // iOS: If you need notification, ask for permission.
  final NotificationPermission notificationPermission =
      await FlutterForegroundTask.checkNotificationPermission();
  if (notificationPermission != NotificationPermission.granted) {
    await FlutterForegroundTask.requestNotificationPermission();
  }

  if (Platform.isAndroid) {
    // Android 12+, there are restrictions on starting a foreground service.
    //
    // To restart the service on device reboot or unexpected problem, you need to allow below permission.
    if (!await FlutterForegroundTask.isIgnoringBatteryOptimizations) {
      // This function requires `android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS` permission.
      await FlutterForegroundTask.requestIgnoreBatteryOptimization();
    }

    // Use this utility only if you provide services that require long-term survival,
    // such as exact alarm service, healthcare service, or Bluetooth communication.
    //
    // This utility requires the "android.permission.SCHEDULE_EXACT_ALARM" permission.
    // Using this permission may make app distribution difficult due to Google policy.
    if (!await FlutterForegroundTask.canScheduleExactAlarms) {
      // When you call this function, will be gone to the settings page. 
      // So you need to explain to the user why set it.
      await FlutterForegroundTask.openAlarmsAndRemindersSettings();
    }
  }
}

void _initService() {
  FlutterForegroundTask.init(
    androidNotificationOptions: AndroidNotificationOptions(
      channelId: 'foreground_service',
      channelName: 'Foreground Service Notification',
      channelDescription:
          'This notification appears when the foreground service is running.',
      onlyAlertOnce: true,
    ),
    iosNotificationOptions: const IOSNotificationOptions(
      showNotification: false,
      playSound: false,
    ),
    foregroundTaskOptions: ForegroundTaskOptions(
      eventAction: ForegroundTaskEventAction.repeat(5000),
      autoRunOnBoot: true,
      autoRunOnMyPackageReplaced: true,
      allowWakeLock: true,
      allowWifiLock: true,
    ),
  );
}

@override
void initState() {
  super.initState();
  // Add a callback to receive data sent from the TaskHandler.
  FlutterForegroundTask.addTaskDataCallback(_onReceiveTaskData);

  WidgetsBinding.instance.addPostFrameCallback((_) {
    // Request permissions and initialize the service.
    _requestPermissions();
    _initService();
  });
}
```

--------------------------------

### Second Page Implementation

Source: https://pub.dev/packages/flutter_foreground_task/example

A simple page demonstrating navigation and popping.

```dart
class SecondPage extends StatelessWidget {
  const SecondPage({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Second Page'),
        centerTitle: true,
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: Navigator.of(context).pop,
          child: const Text('pop this page'),
        ),
      ),
    );
  }
}
```

--------------------------------

### Configure AppDelegate for Swift

Source: https://pub.dev/packages/flutter_foreground_task

Register the plugin callback in the AppDelegate for Swift projects.

```swift
import UIKit
import Flutter

@main
@objc class AppDelegate: FlutterAppDelegate {
  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    GeneratedPluginRegistrant.register(with: self)

    // this
    SwiftFlutterForegroundTaskPlugin.setPluginRegistrantCallback { registry in
      GeneratedPluginRegistrant.register(with: registry)
    }
    if #available(iOS 10.0, *) {
      UNUserNotificationCenter.current().delegate = self as? UNUserNotificationCenterDelegate
    }

    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}
```

--------------------------------

### Configure Info.plist for Background Tasks

Source: https://pub.dev/packages/flutter_foreground_task

Add these keys to ios/Runner/info.plist to enable background task execution and fetch modes.

```xml
<key>BGTaskSchedulerPermittedIdentifiers</key>
<array>
    <string>com.pravera.flutter_foreground_task.refresh</string>
</array>
<key>UIBackgroundModes</key>
<array>
    <string>fetch</string>
</array>
```

--------------------------------

### Add dependency via command line

Source: https://pub.dev/packages/flutter_foreground_task/install

Use this command in your terminal to automatically add the package to your project.

```bash
$ flutter pub add flutter_foreground_task
```

--------------------------------

### Build UI Components

Source: https://pub.dev/packages/flutter_foreground_task/example

Helper methods to build the communication data display and service control buttons.

```dart
  Widget _buildCommunicationDataText() {
    return ValueListenableBuilder(
      valueListenable: _taskDataListenable,
      builder: (context, data, _) {
        return Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              const Text('You received data from TaskHandler:'),
              Text('$data', style: Theme.of(context).textTheme.headlineMedium),
            ],
          ),
        );
      },
    );
  }

  Widget _buildServiceControlButtons() {
    buttonBuilder(String text, {VoidCallback? onPressed}) {
      return ElevatedButton(
        onPressed: onPressed,
        child: Text(text),
      );
    }

    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          buttonBuilder('start service', onPressed: _startService),
          buttonBuilder('stop service', onPressed: _stopService),
          buttonBuilder('increment count', onPressed: _incrementCount),
        ],
      ),
    );
  }
```

--------------------------------

### Initialize Foreground Service

Source: https://pub.dev/packages/flutter_foreground_task/example

Configures Android and iOS notification settings and task options for the foreground service.

```dart
  void _initService() {
    FlutterForegroundTask.init(
      androidNotificationOptions: AndroidNotificationOptions(
        channelId: 'foreground_service',
        channelName: 'Foreground Service Notification',
        channelDescription:
            'This notification appears when the foreground service is running.',
        onlyAlertOnce: true,
      ),
      iosNotificationOptions: const IOSNotificationOptions(
        showNotification: false,
        playSound: false,
      ),
      foregroundTaskOptions: ForegroundTaskOptions(
        eventAction: ForegroundTaskEventAction.repeat(5000),
        autoRunOnBoot: true,
        autoRunOnMyPackageReplaced: true,
        allowWakeLock: true,
        allowWifiLock: true,
      ),
    );
  }
```

--------------------------------

### Handle Streams in TaskHandler

Source: https://pub.dev/packages/flutter_foreground_task

Demonstrates managing stream subscriptions within a TaskHandler, ensuring proper cleanup in onDestroy.

```dart
class MyTaskHandler extends TaskHandler {
  StreamSubscription<Location>? _streamSubscription;

  @override
  Future<void> onStart(DateTime timestamp, TaskStarter starter) async {
    _streamSubscription = FlLocation.getLocationStream().listen((location) {
      final String message = '${location.latitude}, ${location.longitude}';
      FlutterForegroundTask.updateService(notificationText: message);

      // Send data to main isolate.
      final String locationJson = jsonEncode(location.toJson());
      FlutterForegroundTask.sendDataToMain(locationJson);
    });
  }

  @override
  void onRepeatEvent(DateTime timestamp) {
    // not use
  }

  @override
  Future<void> onDestroy(DateTime timestamp, bool isTimeout) async {
    _streamSubscription?.cancel();
    _streamSubscription = null;
  }
}
```

--------------------------------

### Configure AppDelegate for Objective-C

Source: https://pub.dev/packages/flutter_foreground_task

Register the plugin callback in the AppDelegate for Objective-C projects.

```objective-c
#import "AppDelegate.h"
#import "GeneratedPluginRegistrant.h"

// this
#import <flutter_foreground_task/FlutterForegroundTaskPlugin.h>

// this
void registerPlugins(NSObject<FlutterPluginRegistry>* registry) {
  [GeneratedPluginRegistrant registerWithRegistry:registry];
}

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application
    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  [GeneratedPluginRegistrant registerWithRegistry:self];

  // this
  [FlutterForegroundTaskPlugin setPluginRegistrantCallback:registerPlugins];
  if (@available(iOS 10.0, *)) {
    [UNUserNotificationCenter currentNotificationCenter].delegate = (id<UNUserNotificationCenterDelegate>) self;
  }

  return [super application:application didFinishLaunchingWithOptions:launchOptions];
}

@end
```

--------------------------------

### Define Task Handlers and Options

Source: https://pub.dev/packages/flutter_foreground_task

Configures foreground task options and implements TaskHandler classes to manage background events and service updates.

```dart
final ForegroundTaskOptions defaultTaskOptions = ForegroundTaskOptions(
  eventAction: ForegroundTaskEventAction.repeat(5000),
  autoRunOnBoot: true,
  autoRunOnMyPackageReplaced: true,
  allowWakeLock: true,
  allowWifiLock: true,
);

@pragma('vm:entry-point')
void startCallback() {
  FlutterForegroundTask.setTaskHandler(FirstTaskHandler());
}

class FirstTaskHandler extends TaskHandler {
  int _count = 0;

  @override
  Future<void> onStart(DateTime timestamp, TaskStarter starter) async {
    // some code
  }

  @override
  void onRepeatEvent(DateTime timestamp) {
    _count++;
    
    if (_count == 10) {
      FlutterForegroundTask.updateService(
        foregroundTaskOptions: defaultTaskOptions.copyWith(
          eventAction: ForegroundTaskEventAction.repeat(1000),
        ),
        callback: updateCallback,
      );
      return;
    }
    
    FlutterForegroundTask.updateService(
      notificationTitle: 'Hello FirstTaskHandler :)',
      notificationText: timestamp.toString(),
    );

    // Send data to main isolate.
    final Map<String, dynamic> data = {
      "timestampMillis": timestamp.millisecondsSinceEpoch,
    };
    FlutterForegroundTask.sendDataToMain(data);
  }

  @override
  Future<void> onDestroy(DateTime timestamp, bool isTimeout) async {
    // some code
  }
}

@pragma('vm:entry-point')
void updateCallback() {
  FlutterForegroundTask.setTaskHandler(SecondTaskHandler());
}

class SecondTaskHandler extends TaskHandler {
  @override
  Future<void> onStart(DateTime timestamp, TaskStarter starter) async {
    // some code
  }

  @override
  void onRepeatEvent(DateTime timestamp) {
    FlutterForegroundTask.updateService(
      notificationTitle: 'Hello SecondTaskHandler :)',
      notificationText: timestamp.toString(),
    );

    // Send data to main isolate.
    final Map<String, dynamic> data = {
      "timestampMillis": timestamp.millisecondsSinceEpoch,
    };
    FlutterForegroundTask.sendDataToMain(data);
  }

  @override
  Future<void> onDestroy(DateTime timestamp, bool isTimeout) async {
    // some code
  }
}
```

--------------------------------

### Configure Bridging Header for Swift

Source: https://pub.dev/packages/flutter_foreground_task

Add the import statement to the Runner-Bridging-Header.h file for Swift projects.

```objective-c
#import <flutter_foreground_task/FlutterForegroundTaskPlugin.h>
```

--------------------------------

### Configure AndroidManifest.xml

Source: https://pub.dev/packages/flutter_foreground_task

Declare required permissions and the foreground service component within the application tag.

```xml
<!-- required -->
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

<!-- foregroundServiceType: dataSync -->
<uses-permission android:name="android.permission.FOREGROUND_SERVICE_DATA_SYNC" />

<!-- foregroundServiceType: remoteMessaging -->
<uses-permission android:name="android.permission.FOREGROUND_SERVICE_REMOTE_MESSAGING" />

<!-- Warning: Do not change service name. -->
<service 
    android:name="com.pravera.flutter_foreground_task.service.ForegroundService"
    android:foregroundServiceType="dataSync|remoteMessaging"
    android:exported="false" />
```

--------------------------------

### Import the package

Source: https://pub.dev/packages/flutter_foreground_task/install

Include this import statement in your Dart files to access the package functionality.

```dart
import 'package:flutter_foreground_task/flutter_foreground_task.dart';
```

--------------------------------

### Handle Task Communication

Source: https://pub.dev/packages/flutter_foreground_task/example

Methods for receiving data from the background task and sending commands to it.

```dart
  void _onReceiveTaskData(Object data) {
    print('onReceiveTaskData: $data');
    _taskDataListenable.value = data;
  }

  void _incrementCount() {
    FlutterForegroundTask.sendDataToTask(MyTaskHandler.incrementCountCommand);
  }
```

--------------------------------

### UI Integration with WithForegroundTask

Source: https://pub.dev/packages/flutter_foreground_task/example

Wraps the Scaffold with WithForegroundTask to enable app minimization behavior when the back button is pressed.

```dart
  @override
  Widget build(BuildContext context) {
    // ** optional **
    // A widget that minimize the app without closing it when the user presses
    // the soft back button. It only works when the service is running.
    //
    // This widget must be declared above the [Scaffold] widget.
    return WithForegroundTask(
      child: Scaffold(
        appBar: AppBar(
          title: const Text('Flutter Foreground Task'),
          centerTitle: true,
        ),
        body: SafeArea(
          child: Column(
            children: [
              Expanded(child: _buildCommunicationDataText()),
              _buildServiceControlButtons(),
            ],
          ),
        ),
      ),
    );
  }
```

--------------------------------

### Initialize Communication Port

Source: https://pub.dev/packages/flutter_foreground_task

Call initCommunicationPort in the main function to enable communication between the TaskHandler and the UI.

```dart
void main() {
  // Initialize port for communication between TaskHandler and UI.
  FlutterForegroundTask.initCommunicationPort();
  runApp(const ExampleApp());
}
```

--------------------------------

### Manage Plugin Data Storage

Source: https://pub.dev/packages/flutter_foreground_task

Provides methods for saving, retrieving, and removing data within the plugin's storage scope.

```dart
void function() async {
  await FlutterForegroundTask.getData(key: String);
  await FlutterForegroundTask.getAllData();
  await FlutterForegroundTask.saveData(key: String, value: Object);
  await FlutterForegroundTask.removeData(key: String);
  await FlutterForegroundTask.clearAllData();
}
```

--------------------------------

### Define TaskHandler and Callback

Source: https://pub.dev/packages/flutter_foreground_task

Implement a TaskHandler class and a top-level or static callback function to manage foreground task lifecycle events.

```dart
// The callback function should always be a top-level or static function.
@pragma('vm:entry-point')
void startCallback() {
  FlutterForegroundTask.setTaskHandler(MyTaskHandler());
}

class MyTaskHandler extends TaskHandler {
  // Called when the task is started.
  @override
  Future<void> onStart(DateTime timestamp, TaskStarter starter) async {
    print('onStart(starter: ${starter.name})');
  }

  // Called based on the eventAction set in ForegroundTaskOptions.
  @override
  void onRepeatEvent(DateTime timestamp) {
    // Send data to main isolate.
    final Map<String, dynamic> data = {
      "timestampMillis": timestamp.millisecondsSinceEpoch,
    };
    FlutterForegroundTask.sendDataToMain(data);
  }

  // Called when the task is destroyed.
  @override
  Future<void> onDestroy(DateTime timestamp, bool isTimeout) async {
    print('onDestroy(isTimeout: $isTimeout)');
  }

  // Called when data is sent using `FlutterForegroundTask.sendDataToTask`.
  @override
  void onReceiveData(Object data) {
    print('onReceiveData: $data');
  }

  // Called when the notification button is pressed.
  @override
  void onNotificationButtonPressed(String id) {
    print('onNotificationButtonPressed: $id');
  }

  // Called when the notification itself is pressed.
  @override
  void onNotificationPressed() {
    print('onNotificationPressed');
  }

  // Called when the notification itself is dismissed.
  @override
  void onNotificationDismissed() {
    print('onNotificationDismissed');
  }
}
```

--------------------------------

### Implement Foreground Service Task Handler

Source: https://pub.dev/packages/flutter_foreground_task/example

Defines a custom TaskHandler to manage service lifecycle events and communication. The callback function must be top-level or static.

```dart
import 'dart:async';
import 'dart:io';

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

void main() {
  // Initialize port for communication between TaskHandler and UI.
  FlutterForegroundTask.initCommunicationPort();
  runApp(const ExampleApp());
}

// The callback function should always be a top-level or static function.
@pragma('vm:entry-point')
void startCallback() {
  FlutterForegroundTask.setTaskHandler(MyTaskHandler());
}

class MyTaskHandler extends TaskHandler {
  static const String incrementCountCommand = 'incrementCount';

  int _count = 0;

  void _incrementCount() {
    _count++;

    // Update notification content.
    FlutterForegroundTask.updateService(
      notificationTitle: 'Hello MyTaskHandler :)',
      notificationText: 'count: $_count',
    );

    // Send data to main isolate.
    FlutterForegroundTask.sendDataToMain(_count);
  }

  // Called when the task is started.
  @override
  Future<void> onStart(DateTime timestamp, TaskStarter starter) async {
    print('onStart(starter: ${starter.name})');
    _incrementCount();
  }

  // Called based on the eventAction set in ForegroundTaskOptions.
  @override
  void onRepeatEvent(DateTime timestamp) {
    _incrementCount();
  }

  // Called when the task is destroyed.
  @override
  Future<void> onDestroy(DateTime timestamp, bool isTimeout) async {
    print('onDestroy(isTimeout: $isTimeout)');
  }

  // Called when data is sent using `FlutterForegroundTask.sendDataToTask`.
  @override
  void onReceiveData(Object data) {
    print('onReceiveData: $data');
    if (data == incrementCountCommand) {
      _incrementCount();
    }
  }

  // Called when the notification button is pressed.
  @override
  void onNotificationButtonPressed(String id) {
    print('onNotificationButtonPressed: $id');
  }

  // Called when the notification itself is pressed.
  @override
  void onNotificationPressed() {
    print('onNotificationPressed');
  }

  // Called when the notification itself is dismissed.
  @override
  void onNotificationDismissed() {
    print('onNotificationDismissed');
  }
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      routes: {
        '/': (context) => const ExamplePage(),
        '/second': (context) => const SecondPage(),
      },
      initialRoute: '/',
    );
  }
}

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

  @override
  State<StatefulWidget> createState() => _ExamplePageState();
}

class _ExamplePageState extends State<ExamplePage> {
  final ValueNotifier<Object?> _taskDataListenable = ValueNotifier(null);

  Future<void> _requestPermissions() async {
    // Android 13+, you need to allow notification permission to display foreground service notification.
    //
    // iOS: If you need notification, ask for permission.
    final NotificationPermission notificationPermission =
        await FlutterForegroundTask.checkNotificationPermission();
    if (notificationPermission != NotificationPermission.granted) {
      await FlutterForegroundTask.requestNotificationPermission();
    }

    if (Platform.isAndroid) {
      // Android 12+, there are restrictions on starting a foreground service.
      //
      // To restart the service on device reboot or unexpected problem, you need to allow below permission.
      if (!await FlutterForegroundTask.isIgnoringBatteryOptimizations) {
        // This function requires `android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS` permission.
        await FlutterForegroundTask.requestIgnoreBatteryOptimization();
      }

      // Use this utility only if you provide services that require long-term survival,
      // such as exact alarm service, healthcare service, or Bluetooth communication.
      //
      // This utility requires the "android.permission.SCHEDULE_EXACT_ALARM" permission.
      // Using this permission may make app distribution difficult due to Google policy.
      if (!await FlutterForegroundTask.canScheduleExactAlarms) {
        // When you call this function, will be gone to the settings page.
        // So you need to explain to the user why set it.
        await FlutterForegroundTask.openAlarmsAndRemindersSettings();
      }
    }
  }
```

--------------------------------

### Add dependency to pubspec.yaml

Source: https://pub.dev/packages/flutter_foreground_task/install

Manually add this line to your pubspec.yaml file to include the package in your dependencies.

```yaml
dependencies:
  flutter_foreground_task: ^10.0.0
```

--------------------------------

### Send Data from UI to Task

Source: https://pub.dev/packages/flutter_foreground_task

Sends data from the main UI isolate to the TaskHandler, requiring JSON-compatible formats for Maps.

```dart
// Main(UI)
void _sendDataToTask() {
  // Main(UI) -> TaskHandler
  //
  // The Map collection can only be sent in json format, such as Map<String, dynamic>.
  FlutterForegroundTask.sendDataToTask(Object);
}

// TaskHandler
@override
void onReceiveData(Object data) {
  print('onReceiveData: $data');

  // You can cast it to any type you want using the Collection.cast<T> function.
  if (data is List<dynamic>) {
    final List<int> intList = data.cast<int>();
  }
}
```

--------------------------------

### Lifecycle Integration

Source: https://pub.dev/packages/flutter_foreground_task/example

Registers and removes data callbacks during widget lifecycle events.

```dart
  @override
  void initState() {
    super.initState();
    // Add a callback to receive data sent from the TaskHandler.
    FlutterForegroundTask.addTaskDataCallback(_onReceiveTaskData);

    WidgetsBinding.instance.addPostFrameCallback((_) {
      // Request permissions and initialize the service.
      _requestPermissions();
      _initService();
    });
  }

  @override
  void dispose() {
    // Remove a callback to receive data sent from the TaskHandler.
    FlutterForegroundTask.removeTaskDataCallback(_onReceiveTaskData);
    _taskDataListenable.dispose();
    super.dispose();
  }
```

--------------------------------

### Send Data from Task to UI

Source: https://pub.dev/packages/flutter_foreground_task

Sends primitive data or collections from the TaskHandler to the main UI isolate.

```dart
// TaskHandler
@override
Future<void> onStart(DateTime timestamp, TaskStarter starter) async {
  // TaskHandler -> Main(UI)
  FlutterForegroundTask.sendDataToMain(Object);
}

// Main(UI)
void _onReceiveTaskData(Object data) {
  print('onReceiveTaskData: $data');
}
```

--------------------------------

### Manage Task Data Callbacks

Source: https://pub.dev/packages/flutter_foreground_task

Register and remove data callbacks in the widget lifecycle to handle messages sent from the TaskHandler.

```dart
void _onReceiveTaskData(Object data) {
  if (data is Map<String, dynamic>) {
    final dynamic timestampMillis = data["timestampMillis"];
    if (timestampMillis != null) {
      final DateTime timestamp =
          DateTime.fromMillisecondsSinceEpoch(timestampMillis, isUtc: true);
      print('timestamp: ${timestamp.toString()}');
    }
  }
}

@override
void initState() {
  super.initState();
  // Add a callback to receive data sent from the TaskHandler.
  FlutterForegroundTask.addTaskDataCallback(_onReceiveTaskData);
}

@override
void dispose() {
  // Remove a callback to receive data sent from the TaskHandler.
  FlutterForegroundTask.removeTaskDataCallback(_onReceiveTaskData);
  super.dispose();
}
```

--------------------------------

### Stop Foreground Service

Source: https://pub.dev/packages/flutter_foreground_task

Terminates the active foreground service.

```dart
Future<ServiceRequestResult> _stopService() {
  return FlutterForegroundTask.stopService();
}
```
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