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Offline Speech to Text Without any Popup Dialog in Android

Last Updated : 08 May, 2024
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In this article, we are going to implement an offline speech-to-text functionality in our project. It can work both Online and Offline. When there is no internet connectivity, it will use the pre-stored language model from our mobile device, so it didn’t recognize much clearly but gave good results. When it is Online it recognizes all the words correctly. Note that we are going to implement this project using the Kotlin language

Note: The offline method will not work on those devices whose API Version is less than 23. Also, this application is not meant to be run on emulators.

Step-by-Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that Select Kotlin as the programming language.

Step 2: Adding Permission

To access the mobile device microphone, we have to add RECORD_AUDIO permission in our AndroidManifest.xml file like below:

<uses-permission android:name=”android.permission.RECORD_AUDIO”/>

Step 3: Modify the colors.xml file and Add the Resources

-> Add the Below lines in the colors.xml file.

<color name=”mic_enabled_color”>#0E87E7</color>
<color name=”mic_disabled_color”>#6D6A6A</color>

-> Download the mic icon and add it to res >drawable here in the drawable repository

Step 4: Working with the activity_main.xml file

Go to the activity_main.xml file and refer to the following code. Below is the code for the activity_main.xml file.

activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/speak_output_tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginHorizontal="20dp"
        android:text="Output Text Here..."
        android:textAlignment="center"
        android:textSize="25sp" />

    <ImageView
        android:id="@+id/mic_speak_iv"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:layout_marginTop="20dp"
        android:src="@drawable/mic"
        app:tint="@color/mic_disabled_color" />

</LinearLayout>

Output UI:

Step 5: Working with the MainActivity.kt file

Go to the MainActivity.kt file and refer to the following code. 

Checking Audio Permission:

To get started, we first need to allow the app to access microphone permission. This function will check if the app is able to access the microphone permission or not. If the permission is not granted then it will open the settings directly and from there the user can allow the microphone permission manually. This offline speech to text is not supported for lower API versions i.e., below 23, so here we are first checking the mobile API version by using Build.VERSION.SDK_INT, and here Build.VERSION_CODES.M will return the constant value of M i.e., 23. Replace the package name from the code with your package name(You can find your package name from the AndroidManifest.xml file)

Kotlin
private fun checkAudioPermission() {
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {  // M = 23
            if(ContextCompat.checkSelfPermission(this, "android.permission.RECORD_AUDIO") != PackageManager.PERMISSION_GRANTED) {
                // this will open settings which asks for permission
                val intent = Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS, Uri.parse("package:com.programmingtech.offlinespeechtotext"))
                startActivity(intent)
                Toast.makeText(this, "Allow Microphone Permission", Toast.LENGTH_SHORT).show()
            }
      }
}

The Function which Handles Speech to Text:

This is the main function of our project which handles speech. We have to first create an object of SpeechRecognizer class of current Context i.e., this (If we are using any Fragments, AlertDialog, etc, there we can replace this with context). Then we have to create an intent and attach EXTRA_LANGUAGE_MODEL and LANGUAGE_MODEL_FREE_FORM to the intent. In setRecognitionListener() method we have to override all the necessary functions like below. To get the speech result, we have to use onResults() method and storing the array list output from the Bundle. The element at the first index will give the output of the speech. We can also use useful functions like onBeginningOfSpeech() which runs first before it started listening and onEndOfSpeech() which runs after the result.

Kotlin
private fun startSpeechToText() {
        val speechRecognizer = SpeechRecognizer.createSpeechRecognizer(this)
        val speechRecognizerIntent = Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH)
        speechRecognizerIntent.putExtra(
            RecognizerIntent.EXTRA_LANGUAGE_MODEL,
            RecognizerIntent.LANGUAGE_MODEL_FREE_FORM
        )
        speechRecognizerIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE, Locale.getDefault())

        speechRecognizer.setRecognitionListener(object : RecognitionListener {
            override fun onReadyForSpeech(bundle: Bundle?) {}
            override fun onBeginningOfSpeech() {}
            override fun onRmsChanged(v: Float) {}
            override fun onBufferReceived(bytes: ByteArray?) {}
            override fun onEndOfSpeech() {}
            override fun onError(i: Int) {}

            override fun onResults(bundle: Bundle) {
                val result = bundle.getStringArrayList(SpeechRecognizer.RESULTS_RECOGNITION)
                if (result != null) {
                    // result[0] will give the output of speech
                }
            }            
            override fun onPartialResults(bundle: Bundle) {}
            override fun onEvent(i: Int, bundle: Bundle?) {}
        })      
        // starts listening ...
        speechRecognizer.startListening(speechRecognizerIntent) 
}


MainActivity.kt

Below is the final code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Note: We picked the name of Project/Application as Offline Speech please rename package name with your package name before importing it.

MainActivity.kt
package com.example.offline_speech

import android.content.Intent
import android.content.pm.PackageManager
import android.net.Uri
import android.os.Build
import android.os.Bundle
import android.provider.Settings
import android.speech.RecognitionListener
import android.speech.RecognizerIntent
import android.speech.SpeechRecognizer
import android.widget.ImageView
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.core.content.ContextCompat
import com.example.offline_speech.R
import java.util.Locale


class MainActivity : AppCompatActivity() {

    private lateinit var micIV: ImageView
    private lateinit var outputTV: TextView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        micIV = findViewById(R.id.mic_speak_iv)
        outputTV = findViewById(R.id.speak_output_tv)

        micIV.setOnClickListener {
            checkAudioPermission()
            // changing the color of mic icon, which
            // indicates that it is currently listening
            micIV.setColorFilter(ContextCompat.getColor(this, R.color.mic_enabled_color)) // #FF0E87E7
            startSpeechToText()
        }
    }

    private fun startSpeechToText() {
        val speechRecognizer = SpeechRecognizer.createSpeechRecognizer(this)
        val speechRecognizerIntent = Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH)
        speechRecognizerIntent.putExtra(
            RecognizerIntent.EXTRA_LANGUAGE_MODEL,
            RecognizerIntent.LANGUAGE_MODEL_FREE_FORM
        )
        speechRecognizerIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE, Locale.getDefault())

        speechRecognizer.setRecognitionListener(object : RecognitionListener {
            override fun onReadyForSpeech(bundle: Bundle?) {}
            override fun onBeginningOfSpeech() {}
            override fun onRmsChanged(v: Float) {}
            override fun onBufferReceived(bytes: ByteArray?) {}
            override fun onEndOfSpeech() {
                // changing the color of our mic icon to
                // gray to indicate it is not listening
                micIV.setColorFilter(ContextCompat.getColor(applicationContext, R.color.mic_disabled_color)) // #FF6D6A6A
            }

            override fun onError(errorCode: Int) {
                val message = when (errorCode) {
                    SpeechRecognizer.ERROR_AUDIO -> "Audio recording error"
                    SpeechRecognizer.ERROR_CLIENT -> "Client side error"
                    SpeechRecognizer.ERROR_INSUFFICIENT_PERMISSIONS -> "Insufficient permissions"
                    // Add other cases based on SpeechRecognizer error codes
                    else -> "Unknown error"
                }
                Toast.makeText(applicationContext, "Error occurred: $message", Toast.LENGTH_SHORT).show()
            }


            override fun onResults(bundle: Bundle) {
                val result = bundle.getStringArrayList(SpeechRecognizer.RESULTS_RECOGNITION)
                if (result != null) {
                    // attaching the output
                    // to our textview
                    outputTV.text = result[0]
                }
            }

            override fun onPartialResults(bundle: Bundle) {}
            override fun onEvent(i: Int, bundle: Bundle?) {}

        })
        speechRecognizer.startListening(speechRecognizerIntent)
    }

    private fun checkAudioPermission() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { // M = 23
            if (ContextCompat.checkSelfPermission(this, "android.permission.RECORD_AUDIO") != PackageManager.PERMISSION_GRANTED) {
                val intent = Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS, Uri.parse("package:com.programmingtech.offlinespeechtotext"))
                startActivity(intent)
                Toast.makeText(this, "Allow Microphone Permission", Toast.LENGTH_SHORT).show()
            }
        }
    }
}

Output: Run on Physical Device


Click Here to Learn More about Android Development Using Kotlin



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