public class MainActivity extends AppCompatActivity implements ZXingScannerView.ResultHandler {

    private static final int REQUEST_CAMERA =1;
    private ZXingScannerView scannerView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        scannerView = new ZXingScannerView(this);
        setContentView(scannerView);
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){
            if(checkPermission()){
                Toast.makeText(MainActivity.this, "Permission is granted", Toast.LENGTH_LONG).show();

            }else{
                requestPermission();
            }
        }

    }

class MainActivity : AppCompatActivity(),ResultHandler{
    private var REQUES_CAMERA = 1
    private var scannerView : ZXingScannerView?=null

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        scannerView= findViewById(R.id.scanner)
      
        //Checking permissions
        if(!checkPermission()){
            requestPermissions()
        }
  
        setupScanner()

    }

    private fun setupScanner() {
            scannerView?.startCamera()
            scannerView?.visibility = View.VISIBLE
            (scannerView?.layoutParams as LinearLayout.LayoutParams).weight = 1f;
            try {
                // val num = parseDouble(txtInput?.text?.toString().substring(2,2))
            } catch (e: NumberFormatException) {
                //numeric = false
            }
    }

    private fun checkPermission() : Boolean{
        return         ContextCompat.checkSelfPermission(this@MainActivity, android.Manifest.permission.CAMERA) ==PackageManager.PERMISSION_GRANTED
        }