How to develop a speech recognizer in android without Google API?

This example demonstrates how do I develop a speech recognizer in android without Google API.
Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.
Step 2 − Add the following code to res/layout/activity_main.xml.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:orientation="vertical" >
   <ImageView
      android:id="@+id/imageView1"
      android:layout_width="200dp"
      android:layout_height="200dp"
      android:layout_centerInParent="true"
      android:src="@drawable/ic_mic" />
   <ProgressBar
      android:id="@+id/progressBar1" style="?android:attr/progressBarStyleHorizontal"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_alignParentLeft="true"
      android:layout_below="@+id/toggleButton1"
      android:layout_marginTop="28dp"
      android:paddingLeft="10dp"
      android:paddingRight="10dp" />
   <TextView
      android:id="@+id/textView1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@+id/progressBar1"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="47dp" />
   <ToggleButton
      android:id="@+id/toggleButton1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="26dp"
      android:text="ToggleButton" />
</RelativeLayout>
Step 3 − Add the following code to src/MainActivity.java
package app.com.sample;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.speech.RecognitionListener;
import android.speech.RecognizerIntent;
import android.speech.SpeechRecognizer;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.CompoundButton;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.ToggleButton;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity implements
RecognitionListener {
   private static final int REQUEST_RECORD_PERMISSION = 100;
   private TextView returnedText;
   private ToggleButton toggleButton;
   private ProgressBar progressBar;
   private SpeechRecognizer speech = null;
   private Intent recognizerIntent;
   private String LOG_TAG = "VoiceRecognitionActivity";
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      returnedText = findViewById(R.id.textView1);
      progressBar = findViewById(R.id.progressBar1);
      toggleButton = findViewById(R.id.toggleButton1);
      progressBar.setVisibility(View.INVISIBLE);
      speech = SpeechRecognizer.createSpeechRecognizer(this);
      Log.i(LOG_TAG, "isRecognitionAvailable: " + SpeechRecognizer.isRecognitionAvailable(this));
      speech.setRecognitionListener(this);
      recognizerIntent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
      recognizerIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_PREFERENCE,"US-en");
      recognizerIntent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
      recognizerIntent.putExtra(RecognizerIntent.EXTRA_MAX_RESULTS, 3);
      toggleButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
         @Override
         public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            if (isChecked) {
               progressBar.setVisibility(View.VISIBLE);
               progressBar.setIndeterminate(true);
               ActivityCompat.requestPermissions (MainActivity.this, new String[]{Manifest.permission.RECORD_AUDIO},
               REQUEST_RECORD_PERMISSION);
            } else {
               progressBar.setIndeterminate(false);
               progressBar.setVisibility(View.INVISIBLE);
               speech.stopListening();
            }
         }
      });
   }
   @Override
   public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
      super.onRequestPermissionsResult(requestCode, permissions, grantResults);
      switch (requestCode) {
         case REQUEST_RECORD_PERMISSION:
         if (grantResults.length > 0 && grantResults[0]== PackageManager.PERMISSION_GRANTED) {
            speech.startListening(recognizerIntent);
         } else {
            Toast.makeText(MainActivity.this, "Permission Denied!", Toast .LENGTH_SHORT).show();
         }
      }
   }
   @Override
   public void onResume() {
      super.onResume();
   }
   @Override
   protected void onPause() {
      super.onPause();
   }
   @Override
   protected void onStop() {
      super.onStop();
      if (speech != null) {
         speech.destroy();
         Log.i(LOG_TAG, "destroy");
      }
   }
   @Override
   public void onBeginningOfSpeech() {
      Log.i(LOG_TAG, "onBeginningOfSpeech");
      progressBar.setIndeterminate(false);
      progressBar.setMax(10);
   }
   @Override
   public void onBufferReceived(byte[] buffer) {
      Log.i(LOG_TAG, "onBufferReceived: " + buffer);
   }
   @Override
   public void onEndOfSpeech() {
      Log.i(LOG_TAG, "onEndOfSpeech");
      progressBar.setIndeterminate(true);
      toggleButton.setChecked(false);
   }
   @Override
   public void onError(int errorCode) {
      String errorMessage = getErrorText(errorCode);
      Log.d(LOG_TAG, "FAILED " + errorMessage);
      returnedText.setText(errorMessage);
      toggleButton.setChecked(false);
   }
   @Override
   public void onEvent(int arg0, Bundle arg1) {
      Log.i(LOG_TAG, "onEvent");
   }
   @Override
   public void onPartialResults(Bundle arg0) {
      Log.i(LOG_TAG, "onPartialResults");
   }
   @Override
   public void onReadyForSpeech(Bundle arg0) {
      Log.i(LOG_TAG, "onReadyForSpeech");
   }
   @Override
   public void onResults(Bundle results) {
      Log.i(LOG_TAG, "onResults");
      ArrayList<String> matches = results .getStringArrayList(SpeechRecognizer.RESULTS_RECOGNITION);
      String text = "";
      for (String result : matches)
         text = result + "\n";
      returnedText.setText(text);
   }
   @Override
   public void onRmsChanged(float rmsdB) {
      Log.i(LOG_TAG, "onRmsChanged: " + rmsdB);
      progressBar.setProgress((int) rmsdB);
   }
   public static String getErrorText(int errorCode) {
      String message;
      switch (errorCode) {
         case SpeechRecognizer.ERROR_AUDIO:
            message = "Audio recording error";
            break;
         case SpeechRecognizer.ERROR_CLIENT:
            message = "Client side error";
            break;
         case
            SpeechRecognizer.ERROR_INSUFFICIENT_PERMISSIONS:
            message = "Insufficient permissions";
            break;
         case SpeechRecognizer.ERROR_NETWORK:
            message = "Network error";
            break;
         case SpeechRecognizer.ERROR_NETWORK_TIMEOUT:
            message = "Network timeout";
            break;
         case SpeechRecognizer.ERROR_NO_MATCH:
            message = "No match";
            break;
         case SpeechRecognizer.ERROR_RECOGNIZER_BUSY:
            message = "RecognitionService busy";
            break;
         case SpeechRecognizer.ERROR_SERVER:
            message = "error from server";
            break;
         case SpeechRecognizer.ERROR_SPEECH_TIMEOUT:
            message = "No speech input";
            break;
         default:
            message = "Didn't understand, please try
            again.";
            break;
      }
      return message;
   }
}
Step 4 − Add the following code to androidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <uses-permission android:name="android.permission.RECORD_AUDIO"/>
   <uses-permission android:name="android.permission.INTERNET" />
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>
Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −
Click here to download the project code.