GoogleSignInClient sample usage

AndroidManifest.xml

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

    <application
            android:allowBackup="true"
            android:icon="@mipmap/ic_launcher"
            android:label="SampleSignIn"
            android:roundIcon="@mipmap/ic_launcher_round"
            android:supportsRtl="true">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>

        <meta-data android:name="com.google.android.gms.games.APP_ID"
                   android:value="PUT_APP_ID_HERE"/>
        <meta-data android:name="com.google.android.gms.version"
                   android:value="@integer/google_play_services_version"/>
    </application>

</manifest>

build.gradle

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "me.change.please"
        minSdkVersion 22
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.google.firebase:firebase-core:16.0.7'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.google.android.gms:play-services-auth:16.0.1'
    implementation 'com.google.android.gms:play-services-games:17.0.0'
}

MainActivity.java

package me.change.please;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.util.Log;
import android.view.View;
import com.google.android.gms.auth.api.signin.GoogleSignIn;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInClient;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;

public final class MainActivity extends Activity implements View.OnClickListener {
    private static final String TAG = "SampleSignIn";
    private static final int RC_SIGN_IN = 9001;

    private GoogleSignInClient mGoogleSignInClient;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mGoogleSignInClient = GoogleSignIn.getClient(this, GoogleSignInOptions.DEFAULT_GAMES_SIGN_IN);

        findViewById(R.id.sign_in).setOnClickListener(this);
        findViewById(R.id.sign_out).setOnClickListener(this);
    }

    @Override
    public void onResume() {
        super.onResume();
        silentSignIn();
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case RC_SIGN_IN: {
                GoogleSignIn.getSignedInAccountFromIntent(data)
                        .addOnSuccessListener(this, new OnSuccessListener<GoogleSignInAccount>() {
                            @Override
                            public void onSuccess(GoogleSignInAccount account) {
                                Log.d(TAG, "Sign in success");
                                onSignIn(account);
                            }
                        })
                        .addOnFailureListener(this, new OnFailureListener() {
                            @Override
                            public void onFailure(@NonNull Exception e) {
                                Log.e(TAG, "Sign in failed", e);
                            }
                        });
                break;
            }
        }
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.sign_in: {
                signIn();
                break;
            }
            case R.id.sign_out: {
                signOut();
                break;
            }
        }
    }

    private void silentSignIn() {
        mGoogleSignInClient.silentSignIn()
                .addOnSuccessListener(this, new OnSuccessListener<GoogleSignInAccount>() {
                    @Override
                    public void onSuccess(GoogleSignInAccount account) {
                        Log.d(TAG, "Silent sign in success");
                        onSignIn(account);
                    }
                })
                .addOnFailureListener(this, new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.e(TAG, "Silent sign in failed", e);
                    }
                });
    }

    private void signIn() {
        startActivityForResult(mGoogleSignInClient.getSignInIntent(), RC_SIGN_IN);
    }

    private void signOut() {
        mGoogleSignInClient.signOut()
                .addOnSuccessListener(this, new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        Log.d(TAG, "Sign out success");
                    }
                })
                .addOnFailureListener(this, new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.e(TAG, "Sign out failed", e);
                    }
                });
    }

    private void onSignIn(GoogleSignInAccount account) {
        final GamesClient gamesClient = Games.getGamesClient(this, account);
        gamesClient.setViewForPopups(findViewById(android.R.id.content));
        gamesClient.setGravityForPopups(Gravity.TOP | Gravity.CENTER_HORIZONTAL);
    }
}