// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {

    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.0'
        classpath 'com.google.gms:google-services:4.2.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'
com.google.gms.googleservices.GoogleServicesPlugin.config.disableVersionCheck = true

android {
    compileSdkVersion 28
    buildToolsVersion "28.0.3"
    defaultConfig {
        applicationId "com.***"
        minSdkVersion 19
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        vectorDrawables.useSupportLibrary = true
        multiDexEnabled = true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    //noinspection GradleCompatible
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support:recyclerview-v7:28.0.0'
    implementation 'com.android.support:design:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
...
    implementation('com.google.android.gms:play-services-base:16.0.1') {
        exclude module: 'support-v4'
    }

    implementation('com.google.android.gms:play-services-maps:16.0.0') {
        exclude module: 'support-v4'
    }

    implementation('com.google.android.gms:play-services-places:16.0.0') {
        exclude module: 'support-v4'
    }
    implementation 'com.google.firebase:firebase-core:16.0.6'
    implementation 'com.google.firebase:firebase-iid:17.0.4'
    implementation 'com.google.firebase:firebase-messaging:17.3.4'
}

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

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

    <application
        android:name=".ApplicationClass"
        android:allowBackup="true"
        android:icon="@drawable/app_icon"
        android:label="@string/app_name"
        android:roundIcon="@drawable/app_icon"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity
            android:name=".MainActivity"
            android:theme="@style/Theme.AppCompat.Light.NoActionBar"/>

        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="***"/>

        <activity
            android:name=".LoginActivity"
            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>
        <service
            android:name=".MyFirebaseInstanceIDService"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT"/>
            </intent-filter>
        </service>
        <meta-data
          android:name="com.google.firebase.messaging.default_notification_icon"
            android:resource="@drawable/logo" />
    </application>
</manifest>

FirebaseInstanceId.getInstance().getInstanceId().addOnSuccessListener(new OnSuccessListener<InstanceIdResult>() {
        @Override
        public void onSuccess(InstanceIdResult instanceIdResult) {
            refreshedToken = instanceIdResult.getToken();
            Log.e("refreshedToken", refreshedToken);
            // Do whatever you want with your token now
            // i.e. store it on SharedPreferences or DB
            // or directly send it to server
        }
    });