How to display a toast message with the displayName after Facebook login with Firebase?

Question

In my app it is possible to login with Facebook and after the successful login I want to display a toast message which says "Welcome back, username (which is the displayName)". I managed to display a message but without the username since I don't know how to get it from Firebase and display it after the login.

Here is the code that handles the Facebook login:

private void handleFacebookAccessToken(AccessToken token) {
        Log.d(TAG, "handleFacebookAccessToken:" + token);
        progressBar.setVisibility(View.VISIBLE);


        AuthCredential credential = FacebookAuthProvider.getCredential(token.getToken());
        mAuth.signInWithCredential(credential)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            // Sign in success, update UI with the signed-in user's information
                            Log.d(TAG, "signInWithCredential:success");
                            FirebaseUser user = mAuth.getCurrentUser();
                            updateUI(user);

// Todo make a toast with the username
                            Toast.makeText(SignInActivity.this, "Welcome back", Toast.LENGTH_SHORT).show();
                        } else {
                            // If sign in fails, display a message to the user.
                            Log.w(TAG, "signInWithCredential:failure", task.getException());
                            Toast.makeText(SignInActivity.this, "Error.",
                                    Toast.LENGTH_LONG).show();
                            updateUI(null);
                        }

                        progressBar.setVisibility(View.INVISIBLE);
                    }
                });
    }

Answer 1

Once you have the Facebook access token you can use GraphApi to get user's additional info:

val request = GraphRequest.newMeRequest(
            accessToken
        ) { user, _ ->
            try {
                val name = user.getString("name")
                Toast.makeText(context, "Hello, $name!", Toast.LENGTH_SHORT).show()
            } catch (e: JSONException) {
                Timber.d("Unable to get user name")
            }
        }
val parameters = Bundle()
parameters.putString("fields", "name")
request.parameters = parameters
request.executeAsync()

Here' code snippets in java

public void requestData(){
        GraphRequest request = GraphRequest.newMeRequest(AccessToken.getCurrentAccessToken(), new GraphRequest.GraphJSONObjectCallback() {
            @Override
            public void onCompleted(JSONObject object,GraphResponse response) {

                JSONObject json = response.getJSONObject();
                try {
                    if(json != null){
                        String name = user.getString("name");
                    Toast.makeText(context, "Welcome "+name, Toast.LENGTH_SHORT).show()
                    }

                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });
        Bundle parameters = new Bundle();
        parameters.putString("fields", "id,name,link,email,picture");
        request.setParameters(parameters);
}