Editor

ServerAuthCodeActivity.java

package com.google.samples.quickstart.signin;

import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

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.common.Scopes;
import com.google.android.gms.common.api.ApiException;
import com.google.android.gms.common.api.Scope;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;

/**
 * Demonstrates retrieving an offline access one-time code for the current Google user, which
 * can be exchanged by your server for an access token and refresh token.
 */
public class ServerAuthCodeActivity extends AppCompatActivity implements
        View.OnClickListener {

public static final String TAG = "ServerAuthCodeActivity";
    private static final int RC_GET_AUTH_CODE = 9003;

private GoogleSignInClient mGoogleSignInClient;
    private TextView mAuthCodeTextView;

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

// Views
        mAuthCodeTextView = findViewById(R.id.detail);

// Button click listeners
        findViewById(R.id.sign_in_button).setOnClickListener(this);
        findViewById(R.id.sign_out_button).setOnClickListener(this);
        findViewById(R.id.disconnect_button).setOnClickListener(this);

// For sample only: make sure there is a valid server client ID.
        validateServerClientID();

// [START configure_signin]
        // Configure sign-in to request offline access to the user's ID, basic
        // profile, and Google Drive. The first time you request a code you will
        // be able to exchange it for an access token and refresh token, which
        // you should store. In subsequent calls, the code will only result in
        // an access token. By asking for profile access (through
        // DEFAULT_SIGN_IN) you will also get an ID Token as a result of the
        // code exchange.
        String serverClientId = getString(R.string.server_client_id);
        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestScopes(new Scope(Scopes.DRIVE_APPFOLDER))
                .requestServerAuthCode(serverClientId)
                .requestEmail()
                .build();
        // [END configure_signin]

mGoogleSignInClient = GoogleSignIn.getClient(this, gso);
    }

private void getAuthCode() {
        // Start the retrieval process for a server auth code.  If requested, ask for a refresh
        // token.  Otherwise, only get an access token if a refresh token has been previously
        // retrieved.  Getting a new access token for an existing grant does not require
        // user consent.
        Intent signInIntent = mGoogleSignInClient.getSignInIntent();
        startActivityForResult(signInIntent, RC_GET_AUTH_CODE);
    }

private void signOut() {
        mGoogleSignInClient.signOut().addOnCompleteListener(this, new OnCompleteListener<Void>() {
            @Override
            public void onComplete(@NonNull Task<Void> task) {
                updateUI(null);
            }
        });
    }

private void revokeAccess() {
        mGoogleSignInClient.revokeAccess().addOnCompleteListener(this,
                new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {
                        updateUI(null);
                    }
                });
    }

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

if (requestCode == RC_GET_AUTH_CODE) {
            // [START get_auth_code]
            Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
            try {
                GoogleSignInAccount account = task.getResult(ApiException.class);
                String authCode = account.getServerAuthCode();

// Show signed-un UI
                updateUI(account);

// TODO(developer): send code to server and exchange for access/refresh/ID tokens
            } catch (ApiException e) {
                Log.w(TAG, "Sign-in failed", e);
                updateUI(null);
            }
            // [END get_auth_code]
        }
    }

private void updateUI(@Nullable GoogleSignInAccount account) {
        if (account != null) {
            ((TextView) findViewById(R.id.status)).setText(R.string.signed_in);

findViewById(R.id.sign_in_button).setVisibility(View.GONE);
            findViewById(R.id.sign_out_and_disconnect).setVisibility(View.VISIBLE);

String authCode = account.getServerAuthCode();
            mAuthCodeTextView.setText(getString(R.string.auth_code_fmt, authCode));
        } else {
            ((TextView) findViewById(R.id.status)).setText(R.string.signed_out);
            mAuthCodeTextView.setText(getString(R.string.auth_code_fmt, "null"));

findViewById(R.id.sign_in_button).setVisibility(View.VISIBLE);
            findViewById(R.id.sign_out_and_disconnect).setVisibility(View.GONE);
        }
    }

/**
     * Validates that there is a reasonable server client ID in strings.xml, this is only needed
     * to make sure users of this sample follow the README.
     */
    private void validateServerClientID() {
        String serverClientId = getString(R.string.server_client_id);
        String suffix = ".apps.googleusercontent.com";
        if (!serverClientId.trim().endsWith(suffix)) {
            String message = "Invalid server client ID in strings.xml, must end with " + suffix;

Log.w(TAG, message);
            Toast.makeText(this, message, Toast.LENGTH_LONG).show();
        }
    }

@Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.sign_in_button:
                getAuthCode();
                break;
            case R.id.sign_out_button:
                signOut();
                break;
            case R.id.disconnect_button:
                revokeAccess();
                break;
        }
    }
}