How to link Google + signed in users on Parse backend on Android?

This seems to be similar with How to create a parse _User account from a Android Google token?

Following is my answer in that thread:

1. New User

The flow is as below:

1. User authorizes and a token is acquired
2. We create a new user with a random password

You can create a ParseUser using following code inside the newChooseAccountIntent() method that return email.

ParseUser user = new ParseUser();user.setUsername(mEmail);user.setPassword(randomPassword);user.setEmail(mEmail);user.signUpInBackground(new SignUpCallback() {  public void done(ParseException e) {    if (e == null) {      // Hooray! Let them use the app now.    } else {      // Sign up didn't succeed. Look at the ParseException      // to figure out what went wrong    }  }});

2. Returning User

This is the where most of people stuck, as I researched over the Internet. The flow is as below:

1. User authorizes and the app gets a token
2. We pass this token to Cloud Code to validate. We need to check if this token is signed by Google and if it is meant for us (android-developers (2013)).
3. After you can verify that the token is valid, you can query for the user in Cloud Code using Parse.Cloud.useMasterKey() method and return the session key by using getSessionToken() method on the query result.
4. Use the session key to save login state on disk by calling becomeInBackground method

To validate the token, you can send Parse.Cloud.httprequest to this endpoint: https://www.googleapis.com/oauth2/v3/tokeninfo?access_token=. This is instructed in Google Identity Documentation. You will receive data as below:

{ "iss": "https://accounts.google.com", "sub": "110169484474386276334", "azp": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com", "email": "billd1600@gmail.com", "at_hash": "X_B3Z3Fi4udZ2mf75RWo3w", "email_verified": "true", "aud": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com", "iat": "1433978353", "exp": "1433981953"}

Things need to compare are "aud", "azp" and "email" which are translated as audience, authorized party and email.

To query for the current user on Cloud Code:

var query = new Parse.Query(Parse.User);query.equalTo("email",mEmail);query.first({  success: function(user) {    // Use user..getSessionToken() to get a session token  },  error: function(user, error) {    //  },  useMasterKey: true});

Note: Make sure you have following scope so that the email will show up when you check on Cloud Code: https://www.googleapis.com/auth/plus.profile.emails.read

There's a question about this on Parse's questions. It's right here and I'm pretty sure it answers your questions.

https://parse.com/questions/google-plus

It links to the parse blog, that has some workarounds on this.

It says that you can add any login into ParseUser. You would be doing something like this:

Parse.User.become("session-token-here").then(function (user) {// The current user is now set to user.}, function (error) {// The token could not be validated.});

Another site where you should take a look:https://parse.com/tutorials/adding-third-party-authentication-to-your-web-app

This last one is official and has an example code

void createNewGPlusUser(final String email, String name) {        final ParseUser user = new ParseUser();        user.setUsername(email);        user.setPassword("my pass");        user.put("any other variable in User class", "value");        user.setEmail(email);        user.put("name", name);        signInParseUser(user, email);    }void signInParseUser(final ParseUser user, final String email) {        user.signUpInBackground(new SignUpCallback() {            public void done(ParseException e) {                if (e == null) {                    Log.d("TAG", "Created user");                    // Hooray! Let them use the app now.                    login(email);                } else {                    Log.d("TAG", "Failed Creating user");                    e.printStackTrace();                    // Sign up didn't succeed. Look at the ParseException                    // to figure out what went wrong                }            }        });    }void login(final String email) {        ParseUser.logInInBackground(email, "my pass", new LogInCallback() {            public void done(ParseUser user, ParseException e) {                if (user != null) {                    // Hooray! The user is logged in.                    Log.d("TAG", "Login successful");                                    } else {                                        // Signup failed. Look at the ParseException to see what happened.                }            }        });    }