ScanActivity.java

package com.example.cs4433qr;

import androidx.appcompat.app.AppCompatActivity;

import android.Manifest;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

import com.google.zxing.Result;
import com.karumi.dexter.Dexter;
import com.karumi.dexter.PermissionToken;
import com.karumi.dexter.listener.PermissionDeniedResponse;
import com.karumi.dexter.listener.PermissionGrantedResponse;
import com.karumi.dexter.listener.PermissionRequest;
import com.karumi.dexter.listener.single.PermissionListener;

import me.dm7.barcodescanner.zxing.ZXingScannerView;

public class ScanActivity extends AppCompatActivity implements ZXingScannerView.ResultHandler {
    TextView scanned;

    ZXingScannerView scannerView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scan);
        //Init
        scanned = findViewById(R.id.scanned);
        scannerView = (ZXingScannerView)findViewById(R.id.zxScan);

        //request permission
        Dexter.withActivity(this)
                .withPermission(Manifest.permission.CAMERA)
                .withListener(new PermissionListener() {
                    @Override
                    public void onPermissionGranted(PermissionGrantedResponse response) {
                        scannerView.setResultHandler(ScanActivity.this);
                        scannerView.startCamera();
                    }

                    @Override
                    public void onPermissionDenied(PermissionDeniedResponse response) {
                        Toast.makeText(ScanActivity.this, "Must Accept Permission", Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onPermissionRationaleShouldBeShown(PermissionRequest permission, PermissionToken token) {

                    }
                }).check();


    }

    @Override
    protected void onDestroy() {
        scannerView.stopCamera();
        super.onDestroy();
    }

    @Override
    public void handleResult(Result result) {
        //here we can receive results
        scanned.setText(result.getText());
    }
}