¿Cómo integrar la biblioteca ZXing a Android Studio para escanear Códigos de barras?

Necesita agregar lo siguiente a su archivo build.gradle:

repositories {
    mavenCentral()

    maven {
        url "http://dl.bintray.com/journeyapps/maven"
    }
}

dependencies {
    // Supports Android 4.0.3 and later (API level 15)
    compile 'com.journeyapps:zxing-android-embedded:2.0.1@aar'

    // Supports Android 2.1 and later (API level 7), but not optimal for later Android versions.
    // If you only plan on supporting Android 4.0.3 and up, you don't need to include this.
    compile 'com.journeyapps:zxing-android-legacy:2.0.1@aar'

    // Convenience library to launch the scanning and encoding Activities.
    // It automatically picks the best scanning library from the above two, depending on the
    // Android version and what is available.
    compile 'com.journeyapps:zxing-android-integration:2.0.1@aar'

    // Version 3.0.x of zxing core contains some code that is not compatible on Android 2.2 and earlier.
    // This mostly affects encoding, but you should test if you plan to support these versions.
    // Older versions e.g. 2.2 may also work if you need support for older Android versions.
    compile 'com.google.zxing:core:3.0.1'
}

Mi build.gradle archivo así:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "com.myapplication2"
        minSdkVersion 16
        targetSdkVersion 21
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

repositories {
    mavenCentral()

    maven {
        url "https://raw.github.com/embarkmobile/zxing-android-minimal/mvn-repo/maven-repository/"
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:21.0.3'
    // Supports Android 4.0.3 and later (API level 15)
    compile 'com.embarkmobile:zxing-android-minimal:2.0.0@aar'

    // Supports Android 2.1 and later (API level 7), but not optimal for later Android versions.
    // If you only plan on supporting Android 4.0.3 and up, you don't need to include this.
    compile 'com.embarkmobile:zxing-android-legacy:2.0.0@aar'

    // Convenience library to launch the scanning and encoding Activities.
    // It automatically picks the best scanning library from the above two, depending on the
    // Android version and what is available.
    compile 'com.embarkmobile:zxing-android-integration:2.0.0@aar'

    // Version 3.0.x of zxing core contains some code that is not compatible on Android 2.2 and earlier.
    // This mostly affects encoding, but you should test if you plan to support these versions.
    // Older versions e.g. 2.2 may also work if you need support for older Android versions.
    compile 'com.google.zxing:core:3.0.1'
}

El código es aquí.

También, para saber cómo usarlo, por favor refiérase a mi respuesta sobre el Stackoverflow aquí

Contiene método y también código simple que he probado.