Login and sign-up (with Email and Google)

activity_create_account.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/linear_layout_create_account_activity"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".ui.login.CreateAccountActivity">

    <!--Place your logo here-->
    <ImageView
        android:layout_width="100dp"
        android:layout_height="100dp" />

    <android.support.design.widget.TextInputLayout
        android:id="@+id/til_username_create"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textColorHint="@android:color/white"
        android:paddingTop="10dp">
        <EditText
            android:id="@+id/edit_text_username_create"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter username" />
    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/til_email_create"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textColorHint="@android:color/white"
        android:paddingTop="10dp">
        <EditText
            android:id="@+id/edit_text_email_create"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter email" />
    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/til_password_create"
        android:textColorHint="@android:color/white"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="10dp">

        <EditText
            android:id="@+id/edit_text_password_create"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter password"
            android:inputType="textPassword" />
    </android.support.design.widget.TextInputLayout>


    <Button
        android:layout_marginTop="20dp"
        android:id="@+id/btn_create_account_final"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary"
        android:text="Create Account"
        android:textColor="@android:color/white" />

    <LinearLayout
        android:layout_marginTop="20dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_already_have_account"
            android:textColor="@android:color/black"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Already have account?" />

        <TextView
            android:id="@+id/tv_sign_in"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="15dp"
            android:text="Sign in"
            android:textStyle="bold"
            android:textSize="20sp"
            android:textColor="@color/colorAccent"
            />
    </LinearLayout>
</LinearLayout>

activity_login.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/linear_layout_login_activity"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:orientation="vertical"
    android:paddingBottom="16dp"
    android:paddingLeft="16dp"
    android:paddingRight="16dp"
    android:paddingTop="16dp"
    tools:context=".ui.login.LoginActivity">

    <!--Place your logo here-->
    <ImageView
        android:layout_width="100dp"
        android:layout_height="100dp" />

    <android.support.design.widget.TextInputLayout
        android:id="@+id/til_email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textColorHint="@android:color/white"
        android:paddingTop="24dp">

        <EditText
            android:id="@+id/edit_text_email"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter email" />
    </android.support.design.widget.TextInputLayout>

    <android.support.design.widget.TextInputLayout
        android:id="@+id/til_password"
        android:textColorHint="@android:color/white"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="24dp">

        <EditText
            android:id="@+id/edit_text_password"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter password"
            android:inputType="textPassword" />
    </android.support.design.widget.TextInputLayout>


    <Button
        android:id="@+id/login_with_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:background="@color/colorPrimary"
        android:text="Sign in with password"
        android:textColor="@android:color/white" />

    <com.google.android.gms.common.SignInButton
        android:id="@+id/login_with_google"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/margin_small"
        android:gravity="center"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_dont_have_account"
            android:textColor="@android:color/black"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Don't have account?" />

        <TextView
            android:id="@+id/tv_sign_up"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="15dp"
            android:text="Create account"
            android:textStyle="bold"
            android:textSize="20sp"
            android:textColor="@color/colorAccent" />
    </LinearLayout>
</LinearLayout>

AndroidManifest.xml

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

    <uses-permission android:name="android.permission.INTERNET" />
    
    <!-- Replace with your own application name -->
    <application
        android:name=".AppName"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".ui.login.LoginActivity"
            android:label="Login"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".ui.login.CreateAccountActivity"
            android:label="Create Account"
            android:theme="@style/AppTheme.NoActionBar">

        </activity>
        
        </application>

</manifest>

background_loginscreen.png

Place in the drawable folder

BaseActivity.java

import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.LinearLayout;
import com.google.android.gms.auth.api.Auth;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.techpalle.karan.doubtlist.R;

/**
 * BaseActivity class is used as a base class for all activities in the app
 * It implements GoogleApiClient callbacks to enable "Logout" in all activities
 * and defines variables that are being shared across all activities
 */
public abstract class BaseActivity extends AppCompatActivity implements
        GoogleApiClient.OnConnectionFailedListener {

    protected GoogleApiClient mGoogleApiClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        /* Setup the Google API object to allow Google logins */
        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestEmail()
                .build();

        /**
         * Build a GoogleApiClient with access to the Google Sign-In API and the
         * options specified by gso.
         */
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
                .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                .build();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        /* Inflate the menu; this adds items to the action bar if it is present. */
        //getMenuInflater().inflate(R.menu.menu_base, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == android.R.id.home) {
            super.onBackPressed();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
    
    /**
     * Configure your background here
     */
    protected void initializeBackground(LinearLayout linearLayout) {
            linearLayout.setBackgroundResource(R.drawable.background_loginscreen);
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
    }
}

build.gradle

dependencies {
  /* For Google Play Services */
    compile 'com.google.android.gms:play-services-safetynet:8.3.0'
    compile 'com.google.android.gms:play-services-auth:8.3.0'
  }

CreateAccountActivity.java

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;

import com.techpalle.karan.doubtlist.R;
import com.techpalle.karan.doubtlist.ui.BaseActivity;

/**
 * Represents Sign up screen and functionality of the app
 */
public class CreateAccountActivity extends BaseActivity implements View.OnClickListener{
    private static final String LOG_TAG = CreateAccountActivity.class.getSimpleName();
    private ProgressDialog mAuthProgressDialog;
    private EditText mEditTextUsernameCreate, mEditTextEmailCreate, mEditTextPasswordCreate;
    private Button mButtonCreateAccountFinal;
    private TextView mTextViewSignIn;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_create_account);

        /**
         * Link layout elements from XML and setup the progress dialog
         */
        initializeScreen();
    }

    /**
     * Override onCreateOptionsMenu to inflate nothing
     *
     * @param menu The menu with which nothing will happen
     */
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        return true;
    }


    /**
     * Link layout elements from XML and setup the progress dialog
     */
    public void initializeScreen() {
        mTextViewSignIn = (TextView) findViewById(R.id.tv_sign_in);
        mButtonCreateAccountFinal = (Button) findViewById(R.id.btn_create_account_final);
        mEditTextUsernameCreate = (EditText) findViewById(R.id.edit_text_username_create);
        mEditTextEmailCreate = (EditText) findViewById(R.id.edit_text_email_create);
        mEditTextPasswordCreate = (EditText) findViewById(R.id.edit_text_password_create);
        LinearLayout linearLayoutCreateAccountActivity = (LinearLayout) findViewById(R.id.linear_layout_create_account_activity);
        initializeBackground(linearLayoutCreateAccountActivity);

        /* Setup the progress dialog that is displayed later when authenticating with Firebase */
        mAuthProgressDialog = new ProgressDialog(this);
        mAuthProgressDialog.setTitle("Progress Dialog Loading");
        mAuthProgressDialog.setMessage("Creating user with firebase");
        mAuthProgressDialog.setCancelable(false);

        /* Register the event listeners on sign in button and create account view */
        mTextViewSignIn.setOnClickListener(this);
        mButtonCreateAccountFinal.setOnClickListener(this);
    }

    /**
     * onClick listeners implemented for the sign in view and create account button
     * @param view
     */
    @Override
    public void onClick(View view) {
        if(view.getId() == mButtonCreateAccountFinal.getId()){
            onCreateAccountPressed();
        } else if(view.getId() == mTextViewSignIn.getId()){
            onSignInPressed();
        }
    }

    /**
     * Open LoginActivity when user taps on "Sign in" textView
     */
    public void onSignInPressed() {
        Intent intent = new Intent(CreateAccountActivity.this, LoginActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(intent);
        finish();
    }

    /**
     * Create new account using Firebase email/password provider
     */
    public void onCreateAccountPressed() {
        
    }

    /**
     * Creates a new user in Firebase from the Java POJO
     */
    private void createUserInFirebaseHelper(final String encodedEmail) {
    }

    private boolean isEmailValid(String email) {
        return true;
    }

    private boolean isUserNameValid(String userName) {
        return true;
    }

    private boolean isPasswordValid(String password) {
        return true;
    }

    /**
     * Show error toast to users
     */
    private void showErrorToast(String message) {
        Toast.makeText(CreateAccountActivity.this, message, Toast.LENGTH_LONG).show();
    }


}

LoginActivity.java

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.view.inputmethod.EditorInfo;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import com.firebase.client.AuthData;
import com.google.android.gms.auth.GoogleAuthException;
import com.google.android.gms.auth.GoogleAuthUtil;
import com.google.android.gms.auth.UserRecoverableAuthException;
import com.google.android.gms.auth.api.Auth;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInResult;
import com.google.android.gms.auth.api.signin.GoogleSignInStatusCodes;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.Scopes;
import com.google.android.gms.common.SignInButton;
import com.google.android.gms.common.api.Scope;
import com.techpalle.karan.doubtlist.R;
import com.techpalle.karan.doubtlist.ui.BaseActivity;

import java.io.IOException;

/**
 * Represents Sign in screen and functionality of the app
 */
public class LoginActivity extends BaseActivity implements View.OnClickListener{

    private static final String LOG_TAG = LoginActivity.class.getSimpleName();
    /* A dialog that is presented until the Firebase authentication finished. */
    private ProgressDialog mAuthProgressDialog;
    private EditText mEditTextEmailInput, mEditTextPasswordInput;
    private TextView mTextViewSignUp;
    private Button mButtonLoginWithPassword;

    /**
     * Variables related to Google Login
     */
    /* A flag indicating that a PendingIntent is in progress and prevents us from starting further intents. */
    private boolean mGoogleIntentInProgress;
    /* Request code used to invoke sign in user interactions for Google+ */
    public static final int RC_GOOGLE_LOGIN = 1;
    /* A Google account object that is populated if the user signs in with Google */
    GoogleSignInAccount mGoogleAccount;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        /**
         * Link layout elements from XML and setup progress dialog
         */
        initializeScreen();

        /**
         * Call signInPassword() when user taps "Done" keyboard action
         */
        mEditTextPasswordInput.setOnEditorActionListener(new TextView.OnEditorActionListener() {
            @Override
            public boolean onEditorAction(TextView textView, int actionId, KeyEvent keyEvent) {

                if (actionId == EditorInfo.IME_ACTION_DONE || keyEvent.getAction() == KeyEvent.ACTION_DOWN) {
                    signInPassword();
                }
                return true;
            }
        });
    }

    @Override
    protected void onResume() {
        super.onResume();
    }

    @Override
    public void onPause() {
        super.onPause();
    }

    /**
     * Override onCreateOptionsMenu to inflate nothing
     *
     * @param menu The menu with which nothing will happen
     */
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        return true;
    }


    /**
     * Sign in with Password provider when user clicks sign in button
     */

    /**
     * Open CreateAccountActivity when user taps on "Sign up" TextView
     */
    public void onSignUpPressed() {
        Intent intent = new Intent(LoginActivity.this, CreateAccountActivity.class);
        startActivity(intent);
    }

    /**
     * Link layout elements from XML and setup the progress dialog
     */
    public void initializeScreen() {
        mEditTextEmailInput = (EditText) findViewById(R.id.edit_text_email);
        mEditTextPasswordInput = (EditText) findViewById(R.id.edit_text_password);
        mTextViewSignUp = (TextView) findViewById(R.id.tv_sign_up);
        mButtonLoginWithPassword = (Button) findViewById(R.id.login_with_password);
        LinearLayout linearLayoutLoginActivity = (LinearLayout) findViewById(R.id.linear_layout_login_activity);
        initializeBackground(linearLayoutLoginActivity);
        /* Setup the progress dialog that is displayed later when authenticating with Firebase */
        mAuthProgressDialog = new ProgressDialog(this);
        mAuthProgressDialog.setTitle("Progress dialog loading");
        mAuthProgressDialog.setMessage("Authenticating with firebase");
        mAuthProgressDialog.setCancelable(false);
        /* Setup Google Sign In */
        setupGoogleSignIn();
        /* Register the event listeners on login button and create account view */
        mTextViewSignUp.setOnClickListener(this);
        mButtonLoginWithPassword.setOnClickListener(this);
    }


    /**
     * onClick listeners implemented for the login button and create account view
     * @param view
     */
    @Override
    public void onClick(View view) {
        if(view.getId() == mButtonLoginWithPassword.getId()){
            signInPassword();
        } else if(view.getId() == mTextViewSignUp.getId()){
            onSignUpPressed();
        }
    }

    /**
     * Sign in with Password provider (used when user taps "Done" action on keyboard)
     */
    public void signInPassword() {
    }

    /**
     * Helper method that makes sure a user is created if the user
     * logs in with Firebase's email/password provider.
     * @param authData AuthData object returned from onAuthenticated
     */
    private void setAuthenticatedUserPasswordProvider(AuthData authData) {
    }

    /**
     * Helper method that makes sure a user is created if the user
     * logs in with Firebase's Google login provider.
     * @param authData AuthData object returned from onAuthenticated
     */
    private void setAuthenticatedUserGoogle(AuthData authData){

    }

    /**
     * Show error toast to users
     */
    private void showErrorToast(String message) {
        Toast.makeText(LoginActivity.this, message, Toast.LENGTH_LONG).show();
    }


    /**
     * Signs you into ShoppingList++ using the Google Login Provider
     * @param token A Google OAuth access token returned from Google
     */
    private void loginWithGoogle(String token) {
    }

    /**
     * GOOGLE SIGN IN CODE
     *
     * This code is mostly boiler plate from
     * https://developers.google.com/identity/sign-in/android/start-integrating
     * and
     * https://github.com/googlesamples/google-services/blob/master/android/signin/app/src/main/java/com/google/samples/quickstart/signin/SignInActivity.java
     *
     * The big picture steps are:
     * 1. User clicks the sign in with Google button
     * 2. An intent is started for sign in.
     *      - If the connection fails it is caught in the onConnectionFailed callback
     *      - If it finishes, onActivityResult is called with the correct request code.
     * 3. If the sign in was successful, set the mGoogleAccount to the current account and
     * then call get GoogleOAuthTokenAndLogin
     * 4. getGoogleOAuthTokenAndLogin launches an AsyncTask to get an OAuth2 token from Google.
     * 5. Once this token is retrieved it is available to you in the onPostExecute method of
     * the AsyncTask. **This is the token required by Firebase**
     */


    /* Sets up the Google Sign In Button : https://developers.google.com/android/reference/com/google/android/gms/common/SignInButton */
    private void setupGoogleSignIn() {
        SignInButton signInButton = (SignInButton)findViewById(R.id.login_with_google);
        signInButton.setSize(SignInButton.SIZE_WIDE);
        signInButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                onSignInGooglePressed(v);
            }
        });
    }

    /**
     * Sign in with Google plus when user clicks "Sign in with Google" textView (button)
     */
    public void onSignInGooglePressed(View view) {
        Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
        startActivityForResult(signInIntent, RC_GOOGLE_LOGIN);
        mAuthProgressDialog.show();

    }

    @Override
    public void onConnectionFailed(ConnectionResult result) {
        /**
         * An unresolvable error has occurred and Google APIs (including Sign-In) will not
         * be available.
         */
        mAuthProgressDialog.dismiss();
        showErrorToast(result.toString());
    }


    /**
     * This callback is triggered when any startActivityForResult finishes. The requestCode maps to
     * the value passed into startActivityForResult.
     */
    @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_GOOGLE_LOGIN) {
            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            handleSignInResult(result);
        }

    }

    private void handleSignInResult(GoogleSignInResult result) {
        Log.d(LOG_TAG, "handleSignInResult:" + result.isSuccess());
        if (result.isSuccess()) {
            /* Signed in successfully, get the OAuth token */
            mGoogleAccount = result.getSignInAccount();
            getGoogleOAuthTokenAndLogin();


        } else {
            if (result.getStatus().getStatusCode() == GoogleSignInStatusCodes.SIGN_IN_CANCELLED) {
                showErrorToast("The sign in was cancelled. Make sure you're connected to the internet and try again.");
            } else {
                showErrorToast("Error handling the sign in: " + result.getStatus().getStatusMessage());
            }
            mAuthProgressDialog.dismiss();
        }
    }

    /**
     * Gets the GoogleAuthToken and logs in.
     */
    private void getGoogleOAuthTokenAndLogin() {
        /* Get OAuth token in Background */
        AsyncTask<Void, Void, String> task = new AsyncTask<Void, Void, String>() {
            String mErrorMessage = null;

            @Override
            protected String doInBackground(Void... params) {
                String token = null;

                try {
                    String scope = String.format("oauth2:%s", new Scope(Scopes.PROFILE)) + " email";

                    token = GoogleAuthUtil.getToken(LoginActivity.this, mGoogleAccount.getEmail(), scope);
                } catch (IOException transientEx) {
                    /* Network or server error */
                    Log.e(LOG_TAG, "Error authenticating with Google: " + transientEx);
                    mErrorMessage = "Network error: " + transientEx.getMessage();
                } catch (UserRecoverableAuthException e) {
                    Log.w(LOG_TAG, "Recoverable Google OAuth error: " + e.toString());

                    /* We probably need to ask for permissions, so start the intent if there is none pending */
                    if (!mGoogleIntentInProgress) {
                        mGoogleIntentInProgress = true;
                        Intent recover = e.getIntent();
                        startActivityForResult(recover, RC_GOOGLE_LOGIN);
                    }
                } catch (GoogleAuthException authEx) {
                    /* The call is not ever expected to succeed assuming you have already verified that
                     * Google Play services is installed. */
                    Log.e(LOG_TAG, " " + authEx.getMessage(), authEx);
                    mErrorMessage = "Error authenticating with Google: " + authEx.getMessage();
                }
                return token;
            }

            @Override
            protected void onPostExecute(String token) {
                mAuthProgressDialog.dismiss();
                if (token != null) {
                    /* Successfully got OAuth token, now login with Google */
                    loginWithGoogle(token);
                } else if (mErrorMessage != null) {
                    showErrorToast(mErrorMessage);
                }
            }
        };

        task.execute();
    }

}