This guide describes how to set up a native C or C++ game project to use the Play Games Services v2 Native SDK and integrate the[Platform authentication](https://developer.android.com/games/pgs/signin). Integration is required to integrate other Play Games Services[features](https://developer.android.com/games/pgs/overview#features)into your game and to integrate Play Games Services into your[backend game server](https://developer.android.com/games/pgs/android/server-access).

## Supported features

The Play Games Services v2 Native SDK is in beta and only supports the Sign-in service. It doesn't yet support other Play Games Services[features](https://developer.android.com/games/pgs/overview#features).

## API reference documentation

The header files for the SDK contain reference documentation for the APIs. The header files are located in the`include`folder in the SDK files, which are available after you sync your project with SDK repository.

## Requirements

- A game project that uses native C or C++ as the primary programming language.

- Your game project and development environment must have the[Gradle](https://docs.gradle.org/current/userguide/userguide.html)build system set up.

## Before you start

You must[set up Play Games Services](https://developer.android.com/games/pgs/console/setup)in Google Play Console.

## Set up your game project

Complete the following steps to set up your game project.

### Update CMakeLists.txt

In your`CMakeLists.txt`file, add the following code:  

      find_package(com.google.android.gms.games.v2.c REQUIRED CONFIG)

      // link games_static for -DANDROID_STL=c++_static or default
      // link games_shared for -DANDROID_STL=c++_shared
      target_link_libraries(
        app PUBLIC com.google.android.gms.games.v2.c::games_static)

### Update build.gradle

In your app-level`build.gradle`file do the following:

- Make sure the[prefab](https://developer.android.com/reference/tools/gradle-api/4.1/com/android/build/api/dsl/BuildFeatures#prefab)build feature is enabled.

- Add the dependency for the Play Games Services v2 Native SDK:

  - `com.google.android.gms:play-services-games-v2-native-c:17.0.0-beta1`

Here's an example:  

      android {
        ...
        buildFeatures {
          prefab true
        }
        ...
      }
      dependencies {
        ...
        implementation "com.google.android.gms:play-services-games-v2-native-c:17.0.0-beta1"
      }

### Update AndroidManifest.xml

1. In your`AndroidManifest.xml`file, define your Play Games Services project ID. You can do so by adding the following lines to the file:

       <manifest>
         <application>
           <meta-data android:name="com.google.android.gms.games.APP_ID"
                      android:value="@string/game_services_project_id"/>
         </application>
       </manifest>

2. Create a[string resource](https://developer.android.com/guide/topics/resources/string-resource#String)for your project ID. This allows your game to access the ID at build time. To create the resource, create the file<var translate="no">project_root</var>`/app/src/main/res/values/games-ids.xml`, and add the following:

       <?xml version="1.0" encoding="utf-8"?>
       <resources>
           <string name="game_services_project_id"
                   translatable="false"><var translate="no">add<span class="devsite-syntax-w"> </span>your<span class="devsite-syntax-w"> </span>Project<span class="devsite-syntax-w"> </span>ID<span class="devsite-syntax-w"> </span>here</var></string>
       </resources>

3. Build and test your game. If successful, when you launch your game it displays a sign-in prompt or a successful sign-in banner.

## Get the player ID

Your game can access player information for an authenticated player by retrieving their player ID. You can retrieve a player ID by calling the`GetPlayerID`function, which is demonstrated in the following example.
**Note:** For more information about how Player IDs work, visit the topic[here on next generation Player IDs](https://developer.android.com/games/pgs/next-gen-player-ids)  

    #include <assert.h>
    #include "gni/gni.h"
    #include "gni/gni_task.h"
    #include "pgs/pgs_play_games.h"
    #include "pgs/pgs_players_client.h"

    // A callback for a GniTask returned from PgsPlayersClient_getCurrentPlayerId.
    void OnGetCurrentPlayerIdCompleteCallback(GniTask *task, void *user_data) {

       if (!GniTask_isSuccessful(task)) {
          const char *error_message = nullptr;
          GniTask_getErrorMessage(task, &error_message);

          // Log error message here.

          GniString_destroy(error_message);
          GniTask_destroy(task);
          return;
       }

       const char *result = nullptr;
       PgsPlayersClient_getCurrentPlayerId_getResult(task, &result);

       // Log player id here.

       GniString_destroy(result);
       GniTask_destroy(task);
    }

    // Gets the player ID.
    void GetPlayerId(jobject main_activity) {
       static const PgsPlayersClient *players_client =
               PgsPlayGames_getPlayersClient(main_activity);

       GniTask *get_current_player_id_task =
               PgsPlayersClient_getCurrentPlayerId(players_client);
       assert(get_current_player_id_task != nullptr);
       GniTask_addOnCompleteCallback(get_current_player_id_task,
                                     OnGetCurrentPlayerIdCompleteCallback,
                                     nullptr);
    }

    // Entry point for our test app
    void TestPGSNative(JNIEnv *env, jobject main_activity) {
       JavaVM *java_vm;
       env->GetJavaVM(&java_vm);

       GniCore_init(java_vm, main_activity);

       GetPlayerId(main_activity);
    }

## Re-launch the sign-in prompt

If a player declines the initial Play Games Services sign-in prompt that is automatically displayed when your game launches, they may change their mind during the game session. You can re-launch the sign-in prompt by calling`PgsGamesSignInClient_signIn`as long as no players are currently authenticated.

## Game server authorization

Once a player successfully authenticates into to Play Games Services, your game client can request a server authorization code that your backend game server can use to securely communicate with Play Games Services. This allows your game server to retrieve, update, and store data for the authenticated player. You can retrieve the server authorization code by calling the`PgsGamesSignInClient_requestServerSideAccess`function.

For more information, see the[server access guide](https://developer.android.com/games/pgs/android/server-access).