Android : Implementing google pla services API in android

I am trying to implement login with gmail in my app as per this tutorial. However, when i run the app, I get a toast message saying an internal error has occured. Can you help me find out where I am going wrong?Here is my code.

    Button normalBtn,facebkBtn;
    TextView terms;

    SignInButton gmailBtn;

    private boolean gmailSignInClicked;

    private static final int RC_SIGN_IN = 0;

    // Logcat tag
    private static final String TAG = "MainActivity";

    // Profile pic image size in pixels
    private static final int PROFILE_PIC_SIZE = 400;

    // Google client to interact with Google API
    private GoogleApiClient mGoogleApiClient;


    /**
     * A flag indicating that a PendingIntent is in progress and prevents us
     * from starting further intents.
     */
    private boolean mIntentInProgress;

    private boolean mSignInClicked;

    private ConnectionResult mConnectionResult;



    Fragment termsFragment;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_login);

        termsFragment = new TermsFragment();

        terms = (TextView)findViewById(R.id.login_textView_terms);
        normalBtn = (Button)findViewById(R.id.loginbutton);
        facebkBtn = (Button)findViewById(R.id.login_facebook_button);
        gmailBtn = (SignInButton)findViewById(R.id.login_gmail_button);

        // Initializing google plus api client
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this).addApi(Plus.API,Plus.PlusOptions.builder().build())
                .addScope(Plus.SCOPE_PLUS_LOGIN).build();

        normalBtn.setOnClickListener(this);
        terms.setOnClickListener(this);
        facebkBtn.setOnClickListener(this);
        gmailBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.loginbutton:
                Intent mainActivity = new Intent(this, MainActivity.class);
                startActivity(mainActivity);
                break;

            case R.id.login_textView_terms:
                Toast.makeText(this, "Terms", Toast.LENGTH_LONG).show();
                break;

            case R.id.login_facebook_button:
                break;

            case R.id.login_gmail_button:
                Log.w("Onclick","Button is clicked.");
                signInWithGplus();

;                break;
        }
    }



    protected void onStart() {
        super.onStart();
        mGoogleApiClient.connect();
    }

    protected void onStop() {
        super.onStop();
        if (mGoogleApiClient.isConnected()) {
            mGoogleApiClient.disconnect();
        }
    }


    @Override
    public void onConnectionFailed(ConnectionResult result) {
        if (!result.hasResolution()) {
            GooglePlayServicesUtil.getErrorDialog(result.getErrorCode(), this,
                    0).show();
            return;
        }

        if (!mIntentInProgress) {
            // Store the ConnectionResult for later usage
            mConnectionResult = result;

            if (mSignInClicked) {
                // The user has already clicked 'sign-in' so we attempt to
                // resolve all
                // errors until the user is signed in, or they cancel.
                resolveSignInError();
            }
        }

    }

    @Override
    protected void onActivityResult(int requestCode, int responseCode,
                                    Intent intent) {
        if (requestCode == RC_SIGN_IN) {
            if (responseCode != RESULT_OK) {
                mSignInClicked = false;
            }

            mIntentInProgress = false;

            if (!mGoogleApiClient.isConnecting()) {
                mGoogleApiClient.connect();
            }
        }
    }

    @Override
    public void onConnected(Bundle arg0) {
        mSignInClicked = false;
        Toast.makeText(this, "User is connected!", Toast.LENGTH_LONG).show();

        // Get user's information
       // getProfileInformation();

        // Update the UI after signin


    }

    @Override
    public void onConnectionSuspended(int arg0) {
        mGoogleApiClient.connect();
        //updateUI(false);
    }


    /**
     * Sign-in into google
     * */
    private void signInWithGplus() {
        Log.w("signIn with google plus","-------------.");
        if (!mGoogleApiClient.isConnecting()) {
            mSignInClicked = true;
            resolveSignInError();
        }
    }

    /**
     * Method to resolve any signin errors
     * */
    private void resolveSignInError() {
        if (mConnectionResult.hasResolution()) {
            try {
                mIntentInProgress = true;
                mConnectionResult.startResolutionForResult(this, RC_SIGN_IN);
            } catch (IntentSender.SendIntentException e) {
                mIntentInProgress = false;
                mGoogleApiClient.connect();
            }

        }
    }



    /**
     * Fetching user's information name, email, profile pic
     * */
   private void getProfileInformation() {
        try {
            if (Plus.PeopleApi.getCurrentPerson(mGoogleApiClient) != null) {
                Person currentPerson = Plus.PeopleApi
                        .getCurrentPerson(mGoogleApiClient);
                String personName = currentPerson.getDisplayName();
                String personPhotoUrl = currentPerson.getImage().getUrl();
                String personGooglePlusProfile = currentPerson.getUrl();
                String email = Plus.AccountApi.getAccountName(mGoogleApiClient);

                Log.e(TAG, "Name: " + personName + ", plusProfile: "
                        + personGooglePlusProfile + ", email: " + email
                        + ", Image: " + personPhotoUrl);

                //txtName.setText(personName);
               // txtEmail.setText(email);

                // by default the profile url gives 50x50 px image only
                // we can replace the value with whatever dimension we want by
                // replacing sz=X
                personPhotoUrl = personPhotoUrl.substring(0,
                        personPhotoUrl.length() - 2)
                        + PROFILE_PIC_SIZE;

                //new LoadProfileImage(imgProfilePic).execute(personPhotoUrl);

            } else {
                Toast.makeText(getApplicationContext(),
                        "Person information is null", Toast.LENGTH_LONG).show();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * Background Async task to load user profile picture from url
     * */
    private class LoadProfileImage extends AsyncTask<String, Void, Bitmap> {
        ImageView bmImage;

        public LoadProfileImage(ImageView bmImage) {
            this.bmImage = bmImage;
        }

        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Bitmap mIcon11 = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon11 = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon11;
        }

        protected void onPostExecute(Bitmap result) {
            bmImage.setImageBitmap(result);
        }
    }

}