未处理的异常：LateInitializationError：字段“recorderController”尚未初始化

Question

日安，我一直在尝试使用 flutter_background 服务在应用程序后台录制音频，但录制控制器一直说“LateInitializationError：字段‘recorderController’尚未初始化”。

我正在使用 audio_waveforms 来录制音频，这是包https://pub.dev/packages/audio_waveforms

尝试在应用程序后台录制音频

'import 'dart:async';

import 'dart:convert';
import 'dart:io';
import 'dart:ui';
import 'package:audio_waveforms/audio_waveforms.dart';
import 'package:device_info_plus/device_info_plus.dart';
import 'package:ffmpeg_kit_flutter/ffmpeg_kit.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:headset_connection_event/headset_event.dart';
import 'package:path_provider/path_provider.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:speakbit/pages/navbar.dart';
import 'package:intl/intl.dart';
import 'package:speakbit/pages/recorder.dart';
import 'package:speakbit/pages/splash.dart';
import 'package:firebase_core/firebase_core.dart';
 import 
'package:flutter_smart_dialog/flutter_smart_dialog.dart';
import 'package:flutter_background_service/flutter_background_service.dart';
import 'package:flutter_background_service/flutter_background_service.dart';
import 'package:flutter_background_service_android/flutter_background_service_android.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:speakbit/providers/riverpod/backgroundplayProvider.dart';
import 'package:permission_handler/permission_handler.dart';

  void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  await Permission.microphone.request();
  await initializeService();

  runApp(const MyApp());
}

final _headsetPlugin = HeadsetEvent();
HeadsetState? _headsetState;
late Directory directory;

String endtime = '';
String? path2;
// _getDir() async {
//   directory = (await getApplicationDocumentsDirectory());
//   // var file = File(directory.path).path;
//   path2 = 
  "${directory.path}/test${DateTime.now().toIso8601String()}.m4a";

//   print('this is path 2:${path2}');
// }

late final RecorderController recorderController;

Future<void> initializeService() async {
  endtime = DateFormat("hh:mm").format(DateTime.now());
  final service = FlutterBackgroundService();

  /// OPTIONAL, using custom notification channel id
  AndroidNotificationChannel channel = const 
AndroidNotificationChannel(
    'my_foreground', // id
    'MY FOREGROUND SERVICE', // title

    // description
    importance: Importance.low, // importance must be at low or higher level
  );

  final FlutterLocalNotificationsPlugin 
flutterLocalNotificationsPlugin =
      FlutterLocalNotificationsPlugin();

  if (Platform.isIOS) {
    await flutterLocalNotificationsPlugin.initialize(
      const InitializationSettings(iOS: 
DarwinInitializationSettings()),
    );
  }

  await flutterLocalNotificationsPlugin
      .resolvePlatformSpecificImplementation<
          AndroidFlutterLocalNotificationsPlugin>()
      ?.createNotificationChannel(channel);

  await service.configure(
    androidConfiguration: AndroidConfiguration(
      // this will be executed when app is in foreground or background in separated isolate
      onStart: onStart,
      // auto start service
      autoStart: true,
      isForegroundMode: true,

      notificationChannelId: 'my_foreground',
      initialNotificationTitle: 'SpeakBit SERVICE',
      initialNotificationContent: 'Initializing',
      foregroundServiceNotificationId: 888,
    ),
    iosConfiguration: IosConfiguration(
      // auto start service
      autoStart: true,

      // this will be executed when app is in foreground in separated isolate
      onForeground: onStart,

      // you have to enable background fetch capability on xcode project
      onBackground: onIosBackground,
    ),
  );

  service.startService();
}

@pragma('vm:entry-point')
Future<bool> onIosBackground(ServiceInstance service) async {
  WidgetsFlutterBinding.ensureInitialized();
  DartPluginRegistrant.ensureInitialized();

  return true;
}

@pragma('vm:entry-point')
void onStart(ServiceInstance service) async {
  recorderController = RecorderController()
    ..androidEncoder = AndroidEncoder.aac
    ..androidOutputFormat = AndroidOutputFormat.mpeg4
    ..iosEncoder = IosEncoder.kAudioFormatMPEG4AAC
    ..sampleRate = 16000;

  bool isRecording = false;
  // Only available for flutter 3.0.0 and later
  DartPluginRegistrant.ensureInitialized();

  // For flutter prior to version 3.0.0
  // We have to register the plugin manually

  /// OPTIONAL when use custom notification
  final FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin =
      FlutterLocalNotificationsPlugin();

  if (service is AndroidServiceInstance) {
    service.on('setAsForeground').listen((event) {
      service.setAsForegroundService();
    });

    service.on('setAsBackground').listen((event) {
      service.setAsBackgroundService();
    });
  }

  service.on('stopService').listen((event) {
    service.stopSelf();
  });

  // bring to foreground
  Timer.periodic(const Duration(seconds: 10), (timer) async {
    if (service is AndroidServiceInstance) {
      if (await service.isForegroundService()) {
        // _headsetPlugin.getCurrentState.then((val) async {
        //   if (val == HeadsetState.CONNECT) {
        bplay().getDir();
        bplay().startOrStopRecording();

        // SUCCESS
      }

      // }
      // });

      /// OPTIONAL for use custom notification
      /// the notification id must be equals with AndroidConfiguration when you call configure() method.
      flutterLocalNotificationsPlugin.show(
        888,
        'COOL SERVICE',
        'Recording',
        // ignore: prefer_const_constructors
        NotificationDetails(
          // ignore: prefer_const_constructors
          android: AndroidNotificationDetails(
            'my_foreground',
            'SpeakBit SERVICE',
            icon: 'ic_bg_service_small',
            ongoing: true,
          ),
        ),
      );

      // if you don't using custom notification, uncomment this
      // service.setForegroundNotificationInfo(
      //   title: "My App Service",
      //   content: "Recording",
      // );
    }

    /// you can see this log in logcat

    // test using external plugin
  });
  final deviceInfo = DeviceInfoPlugin();
  String? device;
  if (Platform.isAndroid) {
    final androidInfo = await deviceInfo.androidInfo;
    device = androidInfo.model;
  }

  if (Platform.isIOS) {
    final iosInfo = await deviceInfo.iosInfo;
    device = iosInfo.model;
  }

  service.invoke(
    'update',
    {
      "current_date": DateTime.now().toIso8601String(),
      "device": device,
    },
  );
}

这是bplay课

import 'dart:async';

import 'package:audio_waveforms/audio_waveforms.dart';
import 'package:ffmpeg_kit_flutter/ffmpeg_kit.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:riverpod/riverpod.dart';
import 'package:intl/intl.dart';
import 'package:permission_handler/permission_handler.dart';
import '../../main.dart';
import '../../pages/recorder.dart';

class bplay {
  bplay();
  var audiosuper;
  late final RecorderController recorderController;
  String? path2;
  getDir() async {
    directory = (await getApplicationDocumentsDirectory());
    // var file = File(directory.path).path;
    path2 = "${directory.path}/test${DateTime.now().toIso8601String()}.m4a";

    print('this is path 2:${path2}');
  }

  initialiseControllers()async {
    if (await Permission.microphone.request().isGranted) {
       recorderController = RecorderController()
      ..androidEncoder = AndroidEncoder.aac
      ..androidOutputFormat = AndroidOutputFormat.mpeg4
      ..iosEncoder = IosEncoder.kAudioFormatMPEG4AAC
      ..sampleRate = 16000;
    }
   
  }

  void startOrStopRecording() async {
  
      await recorderController.record(path: path2);
      final timer = Timer(Duration(seconds: 10), () async {
        final path = await recorderController.stop(false);

        if (path != null) {
          await audioconverter(path);
        }
        recorderController.setRefresh(false);
        recorderController.reset();
      }).cancel();
    
  }

  Future audioconverter(String audio) async {
    String output1 = '${audio + '.wav'}';
    String command = ' -i ${audio} -af "afftdn=nf=-75:tn=1:nr=30" ${output1}';
    await FFmpegKit.execute(command).then((value) async {
      if (output1 != null) {
        var audiosuper = output1;

        var now = DateTime.now();
        var formatter = DateFormat(' d MMM, yyyy');
        var endtime = DateFormat("hh:mm").format(DateTime.now());
        var formattedDate = formatter.format(now);
        audioList.add(
          {
            'audio': audiosuper,
            'date': formattedDate,
            'time': endtime,
            'super': audiosuper
          },
        );
      }
      // SUCCESS
    });
  }
}

Answer 1

改变

 late final RecorderController recorderController;

到

 final RecorderController recorderController = RecorderController();