Data streaming between Flutter and Java is not working

Question

I am a newbie to flutter and Java. I want help from you guys.

What do I need? I want to make an android mobile application with two buttons. One button to record our voice and another one to stop recording. After clicking a record button I want to record my sound with the help of Microsoft Azure speech-to-text API and get a transcribed text. The text should be then passed to the flutter in real-time and displayed on a screen.

What I have done? I have created a dart file with a text area and two buttons. One button to record sound and another one to stop recording. When I clicked a record button, the Java code will be called with the event channel as I want the speech to text in real-time. The java code will contain a Microsoft azure speech-to-text API and give a text output of the given input voice.

What is my problem? I got a speech-to-text from Microsoft Azure API when I clicked a record button. But the transcribed text is not passing to flutter. I was able to get a hard-coded text to the flutter but I want to get a transcribed text returned back to flutter and it should be real-time also.

I have attached a java code as well as dart files in .txt format which I am using.

Hope you guys will help me to find a solution.

homepage.txt

import 'dart:async';

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

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);
  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  static const stream = EventChannel(
      'com.chamelalaboratory.demo.flutter_event_channel/eventChannel');

  late StreamSubscription _streamSubscription;
  String _currentValue = "";

  void _startListener() {
    _streamSubscription = stream.receiveBroadcastStream().listen(_listenStream);
  }

  void _cancelListener() {
    _streamSubscription.cancel();
    setState(() {
      _currentValue = "Start Recording...";
    });
  }

  void _listenStream(value) {
    debugPrint("Received From Native:  $value\n");
    setState(() {
      _currentValue = value;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: [
            Text(_currentValue.toUpperCase(), textAlign: TextAlign.justify),
            const SizedBox(
              height: 50,
            ),

            //Start Btn
            ElevatedButton(
              onPressed: () => _startListener(),
              child: Text("Record".toUpperCase()),
            ),
            const SizedBox(
              height: 50,
            ),

            //Cancel Btn
            ElevatedButton(
              onPressed: () => _cancelListener(),
              child: Text("Stop".toUpperCase()),
            ),
          ],
        ),
      ),
    );
  }
}

main.txt

import 'package:flutter/material.dart';

import 'home_page.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Event Channel Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Demo page'),
    );
  }
}

mainjavafile.txt

package com.example.sounddiaryapp;

import androidx.annotation.NonNull;
import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;

import com.microsoft.cognitiveservices.speech.*;
import com.microsoft.cognitiveservices.speech.audio.*;

import java.util.concurrent.ExecutionException;
import java.io.IOException;
import java.util.concurrent.Future;

import androidx.core.app.ActivityCompat;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

import java.util.*;  
import java.util.concurrent.Future;
import static android.Manifest.permission.*;
import java.util.concurrent.TimeUnit;

import android.os.Handler;
import java.util.Objects;
import io.flutter.plugin.common.EventChannel;

public class MainActivity extends FlutterActivity {
    private static final String CHANNEL = "codecommon";
    private static String YourSubscriptionKey = "";
    private static String YourServiceRegion = "";

    public static final String STREAM = "com.chamelalaboratory.demo.flutter_event_channel/eventChannel";
    final String TAG_NAME = "From_Native";

    private EventChannel.EventSink attachEvent;
    private int count = 1;
    public String receivedText = "";
    List<String> textList=new ArrayList<String>();  

    private Handler handler;

    SpeechConfig speechConfig = SpeechConfig.fromSubscription(YourSubscriptionKey,
                    YourServiceRegion);

    AudioConfig audioConfig = AudioConfig.fromDefaultMicrophoneInput();
    SpeechRecognizer speechRecognizer  = new SpeechRecognizer(speechConfig, audioConfig);

    private final Runnable runnable = new Runnable() {
        @Override
        public void run() {

            try{
                int requestCode = 5; // unique code for the permission request
                ActivityCompat.requestPermissions(MainActivity.this,
                        new String[] { RECORD_AUDIO, INTERNET }, requestCode);
                
                try {   
                    speechRecognizer.recognized.addEventListener((s, e) -> {
                        if (e.getResult().getReason() == ResultReason.RecognizedSpeech) {
                            System.out.println("RECOGNIZED: Text=" + e.getResult().getText());
                            String receivedText = e.getResult().getText();
                            attachEvent.success(receivedText);
        
                        } else if (e.getResult().getReason() == ResultReason.NoMatch) {
                            System.out.println("NOMATCH: Speech could not be recognized.");
        
                            try {
                                speechRecognizer.stopContinuousRecognitionAsync().get();
                                // attachEvent.endOfStream();
                            }
                            catch (Exception ex ) {
                                System.out.println(ex.getMessage());
                            }
                            
                        }
                    });
        
                    speechRecognizer.canceled.addEventListener((s, e) -> {
                        System.out.println("CANCELED: Reason=" + e.getReason());
        
                        if (e.getReason() == CancellationReason.Error) {
                            System.out.println("CANCELED: ErrorCode=" + e.getErrorCode());
                            System.out.println("CANCELED: ErrorDetails=" + e.getErrorDetails());
                            System.out.println(
                                    "CANCELED: Did you set the speech resource key and region values?");
                        }
        
                        try {
                            speechRecognizer.stopContinuousRecognitionAsync().get();
                            attachEvent.endOfStream();
                        }
                        catch (Exception ex ) {
                            System.out.println(ex.getMessage());
                        }
        
                    });
        
                    speechRecognizer.sessionStopped.addEventListener((s, e) -> {
                        System.out.println("\n    top Session stopped event.");
        
                        try {
                            speechRecognizer.stopContinuousRecognitionAsync().get();
                            // attachEvent.endOfStream();
                        }
                        catch (Exception ex ) {
                            System.out.println(ex.getMessage());
                        }
        
                    });

                    speechRecognizer.startContinuousRecognitionAsync().get();
                    
        
                } catch(Exception e) {
                    System.out.println("*****************************************************");
                    System.out.println(e.getMessage());
                    try {
                        speechRecognizer.stopContinuousRecognitionAsync().get();
                        // attachEvent.endOfStream();
                    }
                    catch (Exception ex ) {
                        System.out.println(ex.getMessage());
                    }
                }

            } catch (Exception ex) {
                System.out.println("+++++++++++++++++++++++++++++ Unexpected exception: " + ex.getMessage());
                // recognizer.stopContinuousRecognitionAsync().get();
                assert (false);
                System.exit(1);
            } 
        }
        
    };
                     

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        new EventChannel(Objects.requireNonNull(getFlutterEngine()).getDartExecutor(), STREAM).setStreamHandler(
                new EventChannel.StreamHandler() {
                    @Override
                    public void onListen(Object args, final EventChannel.EventSink events) {
                        Log.w(TAG_NAME, "Adding listener");
                        attachEvent = events;
                        count = 1;
                        handler = new Handler();
                        runnable.run();
                    }

                    @Override
                    public void onCancel(Object args) {
                        Log.w(TAG_NAME, "Cancelling listener");
                        try{
                            stopSpeechToText();
                        }
                        catch (Exception ex) {
                            System.out.println("-------------------------------------");
                            System.out.println(ex);
                        }
                        
                        handler.removeCallbacks(runnable);
                        handler = null;
                        count = 1;
                        attachEvent = null;
                        System.out.println("StreamHandler - onCancelled: ");
                    }
                }
        );
    }



    public void stopSpeechToText() throws InterruptedException, ExecutionException,IOException {
        speechRecognizer .sessionStopped.addEventListener((s, e) -> {
            System.out.println("\n    top Session stopped event.");

            try {
                speechRecognizer .stopContinuousRecognitionAsync().get();
                // attachEvent.endOfStream();
            }
            catch (Exception ex ) {
                System.out.println(ex.getMessage());
            }

        });

    }


    @Override
    protected void onDestroy() {
        super.onDestroy();
        handler.removeCallbacks(runnable);
        handler = null;
        attachEvent = null;
    }
}