Android Google Maps (Google Play Version 15)

The easiest way is to add Google Maps Activity to your project. Goto File -> New -> Activity -> Gallery and select Google Maps Activity. This will automatically create the following.

NOTE: The tutorial is tested with Android Studio 3.1.

Google Maps Activity

Add google play map depedencies to app Module build.gradle

dependencies {
    // https://developers.google.com/android/guides/releases
    implementation 'com.google.android.gms:play-services-maps:15.0.1'
}

Add permission and API_KEY to AndroidManifest.xml

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

    <application ...>
        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_maps_key" />
    </application>
</manifest>

NOTE: The ACCESS_COARSE/FINE_LOCATION permissions are not required to use Google Maps Android API v2, but you must specify either coarse or fine location permissions for the 'MyLocation' functionality.

res/values/google_maps_api.xml

<resources>
    <!--
    TODO: Before you run your application, you need a Google Maps API key.

    To get one, follow this link, follow the directions and press "Create" at the end:

    https://console.developers.google.com/flows/enableapi?apiid=maps_android_backend&keyType=CLIENT_SIDE_ANDROID&r=A9:60:D2:42:4A:62:20:6A:78:E0:EC:7D:3B:CF:6B:51:15:A1:F1:F0%3Bcom.luasoftware.testgooglemap

    You can also add your credentials to an existing key, using these values:

    Package name:
    A9:60:D2:42:4A:62:20:6A:78:E0:EC:7D:3B:CF:6B:51:15:A1:F1:F0

    SHA-1 certificate fingerprint:
    A9:60:D2:42:4A:62:20:6A:78:E0:EC:7D:3B:CF:6B:51:15:A1:F1:F0

    Alternatively, follow the directions here:
    https://developers.google.com/maps/documentation/android/start#get-key

    Once you have your key (it starts with "AIza"), replace the "google_maps_key"
    string in this file.
    -->

    <string name="google_maps_key" templateMergeStrategy="preserve" translatable="false">YOUR_KEY_HERE</string>
</resources>

This file contain instruction to get Google Maps API key from Google APIs Console.

Use the provided link https://console.developers.google.com/flows/... to create Credentials for API Keys (select existing Google projects or create new).
Copy the API_KEY into res/values/google_maps_api.xml (it starts with AIza)
Select Library from the left panel and enable Maps SDK for Android.

NOTE: At Credentials for API Keys, make sure the package name is correct (e.g. com.luasoftware.testgooglemap). Mine was wrongly put as com.luasoftware.testgooglemap.view because I created the activity in the view package.

NOTE: I suspect the SHA-1 certificate fingerprint provided by default only works for development/debug build only. You probably need to add another SHA-1 certificate fingerprint entry for production build (use keytool -list -v -keystore {keystore.jks} -alias {alias_name} or refer to this guide).

Google Api Android Credentials

Google Api Credentials

Maps SDK for Android

If you bump into the exception of Authorization failure, check if

API_KEY is correct
Package name & SHA-1 is correct in Google APIs Console - Credentials
Maps SDK for Android is enable Google APIs Console - Library

05-08 17:06:57.643 3868-4057/com.luasoftware.pixpin E/Google Maps Android API: Authorization failure.  Please see https://developers.google.com/maps/documentation/android-api/start for how to correctly set up the map.
05-08 17:06:57.653 3868-4057/com.luasoftware.pixpin E/Google Maps Android API: In the Google Developer Console (https://console.developers.google.com)
    Ensure that the "Google Maps Android API v2" is enabled.
    Ensure that the following Android Key exists:
      API Key: AIza***
      Android Application (<cert_fingerprint>;<package_name>): A9:60:***;com.luasoftware.pixpin

Below is a default sample code of loading Google Map in Android.

class MapsActivity : AppCompatActivity(), OnMapReadyCallback {    private lateinit var mMap: GoogleMap    override fun onCreate(savedInstanceState: Bundle?) {        super.onCreate(savedInstanceState)        setContentView(R.layout.activity_maps)        // Obtain the SupportMapFragment and get notified when the map is ready to be used.        val mapFragment = supportFragmentManager                .findFragmentById(R.id.map) as SupportMapFragment        mapFragment.getMapAsync(this)    }    /**     * Manipulates the map once available.     * This callback is triggered when the map is ready to be used.     * This is where we can add markers or lines, add listeners or move the camera. In this case,     * we just add a marker near Sydney, Australia.     * If Google Play services is not installed on the device, the user will be prompted to install     * it inside the SupportMapFragment. This method will only be triggered once the user has     * installed Google Play services and returned to the app.     */    override fun onMapReady(googleMap: GoogleMap) {        mMap = googleMap        // Add a marker in Sydney and move the camera        val sydney = LatLng(-34.0, 151.0)        mMap.addMarker(MarkerOptions().position(sydney).title("Marker in Sydney"))        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney))    }}

res/layour/activity_maps.xml

<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.SupportMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MapsActivity" />

References:

https://developers.google.com/maps/documentation/android-sdk/start