Dialogflow API v2 integration issue

I am using Dialogflow v1 on android but I want to use V2 because it provides more features and because the V1 will be deprecated on October 23, 2019. However I can't integrate API V2 to my codes. Here is the V1 code:

private void initChatbot() {
    final AIConfiguration config = new AIConfiguration("Here put Client access token",
            AIConfiguration.SupportedLanguages.English,
            AIConfiguration.RecognitionEngine.System);
    aiDataService = new AIDataService(this, config);
    customAIServiceContext = AIServiceContextBuilder.buildFromSessionId(uuid);// helps to create new session whenever app restarts
    aiRequest = new AIRequest();
}

Here is the V2 code:

private void initV2Chatbot() {
    try {
        InputStream stream = getResources().openRawResource(R.raw.test_agent_credentials);
        GoogleCredentials credentials = GoogleCredentials.fromStream(stream);
        String projectId = ((ServiceAccountCredentials)credentials).getProjectId();

        SessionsSettings.Builder settingsBuilder = SessionsSettings.newBuilder();
        SessionsSettings sessionsSettings = settingsBuilder.setCredentialsProvider(FixedCredentialsProvider.create(credentials)).build();
        sessionsClient = SessionsClient.create(sessionsSettings);
        session = SessionName.of(projectId, uuid);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

When I wrote this code for V2 got this error:

error: cannot find symbol variable test_agent_credentials

I actually don't know what is test_agent_credentials and why I should use it. Can anybody tell me where I should put my console.cloud.google Dialogflow İntegration Key Id?

Here is the Gradle:

apply plugin: 'com.android.application'

android {
    buildToolsVersion "28.0.3"
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.tyagiabhinav.dialogflowchat"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    repositories {
        mavenCentral()
    }


    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    // Java V2
    packagingOptions {
        exclude 'META-INF/LICENSE'
        exclude 'META-INF/DEPENDENCIES'
        exclude 'META-INF/INDEX.LIST'
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.google.apis:google-api-services-oauth2:v1-rev145-1.25.0'


    // Dialogflow SDK dependencies
    implementation 'ai.api:sdk:2.0.7@aar'
    implementation 'ai.api:libai:1.6.12'

    // Java V2
    implementation 'com.google.cloud:google-cloud-dialogflow:0.67.0-alpha'
    // for Remote Procedure Call to avoid "No functional channel service provider found" error while creating SessionsClient
    implementation 'io.grpc:grpc-okhttp:1.15.1'
}