First get the Configuration File for Sign-in from

Open link below

[https://developers.google.com/identity/sign-in/android/start-integrating][1] (opens new window)

click on get A configuration file

• Enter App name And package name and click on choose and configure services
• provide SHA1 (opens new window) Enable google SIGNIN and generate configuration files

Download the configuration file and place the file in app/ folder of your project

1. Add the dependency to your project-level build.gradle:

classpath 'com.google.gms:google-services:3.0.0'

1. Add the plugin to your app-level build.gradle:(bottom)

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

1. add this dependency to your app gradle file

dependencies { compile 'com.google.android.gms:play-services-auth:9.8.0' }

• In your sign-in activity's onCreate method, configure Google Sign-In to request the user data required by your app.

GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
        .requestEmail()
        .build();

• create a GoogleApiClient object with access to the Google Sign-In API and the options you specified.

mGoogleApiClient = new GoogleApiClient.Builder(this)
        .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
        .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
        .build();

 private void signIn() {
 Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
 startActivityForResult(signInIntent, RC_SIGN_IN);
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
    if (requestCode == RC_SIGN_IN) {
        GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
        handleSignInResult(result);
    }
}

 private void handleSignInResult(GoogleSignInResult result) {
 Log.d(TAG, "handleSignInResult:" + result.isSuccess());
 if (result.isSuccess()) {
     // Signed in successfully, show authenticated UI.
     GoogleSignInAccount acct = result.getSignInAccount();
     mStatusTextView.setText(getString(R.string.signed_in_fmt, acct.getDisplayName()));
     updateUI(true);
 } else {
     // Signed out, show unauthenticated UI.
     updateUI(false);
 }
}