Attempt to invoke virtual method 'android.content.ContentResolver android.content.getContentResolver()' on a null object How to solve this error

Question

1. I got error at this line private TextToSpeech textToSpeech = new TextToSpeech(this, new TextToSpeech.OnInitListener();

2. How to solve Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.ContentResolver android.content.Context.getContentResolver()' on a null object reference

package com.example.software2.texttospeechapp;

import static android.Manifest.permission.CAMERA;

import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.speech.tts.TextToSpeech;
import android.util.SparseArray;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import com.google.android.gms.vision.CameraSource;
import com.google.android.gms.vision.Detector;
import com.google.android.gms.vision.text.TextBlock;
import com.google.android.gms.vision.text.TextRecognizer;

import java.io.IOException;

public class MainActivity2 extends AppCompatActivity {

    private TextView textView;
    private SurfaceView surfaceView;

    private CameraSource cameraSource;
    private TextRecognizer textRecognizer;

    private TextToSpeech textToSpeech = new TextToSpeech(this, new TextToSpeech.OnInitListener() {
        @Override
        public void onInit(int status) {
        }
    });
    private String stringResult = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ActivityCompat.requestPermissions(this, new String[]{CAMERA}, PackageManager.PERMISSION_GRANTED);
    }


    @Override
    protected void onDestroy() {
        super.onDestroy();
        cameraSource.release();
    }

    private void textRecognizer() {
        textRecognizer = new TextRecognizer.Builder(getApplicationContext()).build();
        cameraSource = new CameraSource.Builder(getApplicationContext(), textRecognizer)
                .setFacing(cameraSource.CAMERA_FACING_BACK)
                .setRequestedPreviewSize(1280, 1024)
                .setAutoFocusEnabled(true)
                .setRequestedFps(2.0f)
                .build();


        surfaceView = findViewById(R.id.surfaceView);
        Context context = this;
        surfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder holder) {
                try {
                    if (ActivityCompat.checkSelfPermission(context, CAMERA) != PackageManager.PERMISSION_GRANTED) {
                        return;
                    }

                    cameraSource.start(surfaceView.getHolder());

                } catch (IOException e) {
                    e.printStackTrace();
                }

            }


            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                cameraSource.stop();
            }
        });
    }
    private void capture() {
        textRecognizer.setProcessor(new Detector.Processor<TextBlock>() {
            @Override
            public void release() {
            }

            @Override
            public void receiveDetections(Detector.Detections<TextBlock> detections) {

                SparseArray<TextBlock> sparseArray = detections.getDetectedItems();
                StringBuilder stringBuilder = new StringBuilder();

                for (int i = 0; i<sparseArray.size(); ++i){
                    TextBlock textBlock = sparseArray.valueAt(i);
                    if (textBlock != null && textBlock.getValue() !=null){
                        stringBuilder.append(textBlock.getValue() + " ");

                    }
                }

                final String stringText = stringBuilder.toString();

                Handler handler = new Handler(Looper.getMainLooper());
                handler.post(() -> {
                    stringResult = stringText;
                    resultObtained();
                });
            }
        });
    }

    private void resultObtained(){
        setContentView(R.layout.activity_main);
        textView = findViewById(R.id.textView);
        textView.setText(stringResult);
        textToSpeech.speak(stringResult, TextToSpeech.QUEUE_FLUSH, null, null);
    }


    public void onPause(){
        if(textToSpeech !=null){
            textToSpeech.stop();

        }
        super.onPause();
    }

    public void buttonstart(View view) {
        setContentView(R.layout.surface);
        Button capture = findViewById(R.id.capture);
        capture.setOnClickListener(v -> capture());
        textRecognizer();
    }
}