Barcode scanning on a single screen

There is a google library, this is a codelab of it.

To use just add this dependency to your gradle

compile 'com.google.android.gms:play-services-vision:10.0.1'

Barcode example class

import android.content.Intent;
import android.hardware.Camera;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.util.Log;
import android.util.SparseArray;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;

import com.google.android.gms.vision.Detector;
import com.google.android.gms.vision.barcode.Barcode;
import com.google.android.gms.vision.barcode.BarcodeDetector;

import java.io.IOException;


public class BarcodeScannerActivity extends Activity {

    SurfaceView cameraView;
    BarcodeDetector barcodeDetector;
    CameraSource cameraSource;
    SparseArray<Barcode> barcodes;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_barcodescanner);
        cameraView = (SurfaceView) findViewById(R.id.surface_camera);
        barcodeDetector = new BarcodeDetector.Builder(BarcodeScannerActivity.this)
        //Aqui você escolhe que tipo de leitura ele vai suportar
                .setBarcodeFormats(Barcode.ALL_FORMATS)
                .build();
        setupCamera();
        setupReader();
    }

    private void setupCamera() {

        CameraSource.Builder builder = new CameraSource.Builder(getApplicationContext(), barcodeDetector);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
            builder = builder.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);
        }

        cameraSource = builder.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH).build();
        cameraView.getHolder().addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder surfaceHolder) {
                try {
                    cameraSource.start(cameraView.getHolder());
                } catch (IOException | SecurityException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {

            }

            @Override
            public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
                cameraSource.stop();
            }
        });
    }

    private void setupReader() {
        barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
            @Override
            public void release() {

            }

            @Override
            public void receiveDetections(Detector.Detections<Barcode> detections) {
                //Quando le algum codigo de barra ele cai aqui
                barcodes = detections.getDetectedItems();
                if (barcodes != null && barcodes.size() >= 1) {
                    String barcode = barcodes.valueAt(0).displayValue;

                }
            }
        });
    }

}

Layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">


<SurfaceView
    android:id="@+id/surface_camera"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:fitsSystemWindows="true" />


<TextView
    android:id="@+id/scanText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="ESCANEANDO"
    android:textSize="40sp" />

Complementing Uzias' response: The code reads tickets, but if it is dealer accounts (phone, light, etc.), you should calculate the check digit for each block (Example barcode: link ).

Using the Module 10 , you have this verification code:

private String checksum(String result) {
        //String result = "8462000000046107010901100356713580601131937174";

        String[] sequencias = splitToNChar(result, 11); //divide em blocos de 11

        List<String[]> checked = new ArrayList<>();

        for(String seq : sequencias) { //uma sequência de 11 dígitos
            int soma = 0;

            for(int s = seq.length() -1; s >= 0; s--) { //para cada dígito, da direita para a esquerda

                int dig = Character.getNumericValue(seq.charAt(s)); //o dígito

                if(dig > 0) {

                    String tmp;

                    if(s % 2 == 0) {

                        tmp = String.valueOf(dig * 2);

                        if(tmp.length() > 1) {
                            for(int p = 0; p < tmp.length(); p++) {
                                soma += Character.getNumericValue(tmp.charAt(p));
                            }
                        } else {
                            soma += Integer.parseInt(tmp);
                        }

                    } else {
                        tmp = String.valueOf(dig);

                        soma += Integer.parseInt(tmp);
                    }
                }
            }

            int rest = soma % 10; //módulo 10

            checked.add( new String[]{seq, String.valueOf(10 - rest) } );
        }

        String retorno = "";
        for(String[] code : checked) {
            retorno += code[0] + code[1];
        }
        return retorno;
    }