Android barcode scanner activity that is implemented by Google ML Kit and Fotoapparat library with the Kotlin language

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <io.fotoapparat.view.CameraView
        android:id="@+id/cameraView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <TextView
        android:layout_width="60dp"
        android:layout_height="match_parent"
        android:layout_marginTop="60dp"
        android:layout_marginBottom="60dp"
        android:background="#7F808080"
        app:layout_constraintLeft_toLeftOf="parent"/>

    <TextView
        android:layout_width="60dp"
        android:layout_height="match_parent"
        android:background="#7F808080"
        android:layout_marginTop="60dp"
        android:layout_marginBottom="60dp"
        app:layout_constraintRight_toRightOf="parent"/>

    <TextView
        android:id="@+id/textViewTop"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:background="#7F808080"
        app:layout_constraintTop_toTopOf="parent"/>

    <TextView
        android:id="@+id/textViewBottom"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:background="#7F808080"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <LinearLayout
        android:id="@+id/layScan"
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:gravity="center_vertical"
        android:orientation="vertical"
        android:background="@drawable/rect_grad"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:background="#FF0000"/>

    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.kasabeh.barcode_ml_foto">

    <uses-permission android:name="android.permission.CAMERA"/>

    <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"
            android:theme="@style/Theme.AppCompat.Light.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

build.gradle

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 29

    defaultConfig {
        applicationId "org.kasabeh.barcode_ml_foto"
        minSdkVersion 16
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.core:core-ktx:1.3.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    implementation 'com.google.mlkit:barcode-scanning:16.0.3'
    implementation 'io.fotoapparat:fotoapparat:2.7.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

MainActivity.kt

class MainActivity : AppCompatActivity() {

    private lateinit var fotoapparat: Fotoapparat
    private val barcodeScanner: BarcodeScanner = BarcodeScanning.getClient()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        checkCameraPermission()

        initFrameProcessor()

        val ani = AnimationUtils.loadAnimation(this, R.anim.scan_anim);
        ani.repeatCount = Animation.INFINITE
        layScan.animation = ani
    }

    private fun initFrameProcessor() {
        fotoapparat = Fotoapparat.with(this)
            .into(cameraView)
            .previewScaleType(ScaleType.CenterCrop)
            .frameProcessor { it ->
                val inputImage = InputImage.fromByteArray(it.image, it.size.width, it.size.height, it.rotation, InputImage.IMAGE_FORMAT_NV21)
                barcodeScanner.process(inputImage)
                    .addOnSuccessListener { barCodes ->
                        for (br in barCodes) {
                            val brValue = br.rawValue
                            println(">>>>>>>>>>>> Barcode value is $brValue")
                            fotoapparat.stop()
                            Toast.makeText(this, "Barcode value is $brValue", Toast.LENGTH_LONG).show()
                        }
                    }
                    .addOnFailureListener {
                        println(">>>>>>>>>>>> Error")
                        it.printStackTrace()
                    }
            }
            .build()
    }

    override fun onStart() {
        super.onStart()
        fotoapparat.start()
    }

    override fun onStop() {
        super.onStop()
        fotoapparat.stop()
    }

    private fun checkCameraPermission() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
            != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.CAMERA), 1 )
            Toast.makeText(this, "Camera permission requested. Try again.", Toast.LENGTH_LONG).show()
        }
    }
}

rect_grad.xml

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <gradient
        android:centerColor="#AFFF0000"
        android:endColor="#5FFF0000"
        android:angle="90"
        android:startColor="#5FFF0000"
        android:type="linear">
    </gradient>

</shape>

scan_anim.xml

<?xml version="1.0" encoding="utf-8"?>
<translate
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:interpolator="@android:anim/linear_interpolator"
    android:duration="15000"
    android:fromYDelta="0%p"
    android:toYDelta="100%p" />