AsyncTask's doInBackground returns value before method inside is finished

Issue

I have created a AsyncTask for handling the Sing in. The issue is that Firebase method signInWithEmailAndPassword is completed after the doInBackground has returned value. I wan't my onPostExecute(Boolean task) to respond to whether the login task was successful, but when I check the log messages i can see that onPostExecute() finishes before onComplete(). How can i make my onPostExecute() after the onComplete() and doInBackground() have finished.

The Log messages:

01-07 12:25:43.775 4046-4241/mk.capitalria.jusufi.riaposdeveloper V/SignInActivity: doInBackground() return type is false
01-07 12:25:43.785 4046-4046/mk.capitalria.jusufi.riaposdeveloper V/SignInActivity: onPostExecute() task is false
01-07 12:25:44.965 4046-4046/mk.capitalria.jusufi.riaposdeveloper V/SignInActivity: onComplete task is successful: true
01-07 12:25:44.965 4046-4046/mk.capitalria.jusufi.riaposdeveloper V/SignInActivity: onComplete task is complete: true

The AsyncTask class:

 public class LoginTask extends AsyncTask<String, Void, Boolean> {
        boolean isSuccessful;
        boolean isComplete;
        FirebaseAuth firebaseAuth;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            firebaseAuth = FirebaseAuth.getInstance();

            signInLayout.setVisibility(View.GONE);
            sinInTask.setVisibility(View.VISIBLE);
        }

        @Override
        protected Boolean doInBackground(String... strings) {

            final String email = strings[0];
            final String password = strings[1];

            firebaseAuth.signInWithEmailAndPassword(email, password).
                    addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                        @Override
                        public void onComplete(@NonNull Task<AuthResult> task) {
                            isSuccessful = task.isSuccessful();
                            isComplete = task.isComplete();
                            Log.v(TAG, "onComplete task is successful: " + isSuccessful);
                            Log.v(TAG, "onComplete task is complete: " + isComplete);
                        }
                    });

            Log.v(TAG, "doInBackground() return type is " + (isSuccessful && isComplete));
            return isComplete && isSuccessful;
        }

        @Override
        protected void onPostExecute(Boolean task) {
            super.onPostExecute(task);
                            Log.v(TAG, "onPostExcecute task is: " + task);

            if (!task) {
                sinInTask.setVisibility(View.GONE);
                signInLayout.setVisibility(View.VISIBLE);
                Toast.makeText(SignInActivity.this, "Authentication failed.",
                        Toast.LENGTH_LONG).show();
            } else {
                Intent intent = new Intent(SignInActivity.this, MainActivity.class);
                startActivity(intent);
                finish();
            }
        }
    }

Solution

As was said, you really don't need to use AsyncTask here cause firebaseAuth.signInWithEmailAndPassword() is non-blocking method. It means that your code is executed not step-by-step but in 2 different Threads. That's why you getting onPostExecute first and after when response from Firebase comes it prints onComplete to logs.

If you really want to use AsyncTask you have to wait while signInWithEmailAndPassword returns some value and it can be done in following way.

public class LoginTask extends AsyncTask<String, Void, Boolean> {
    boolean isSuccessful;
    boolean isComplete;
    FirebaseAuth firebaseAuth;

    final ReentrantLock loginLock = new ReentrantLock();

    ...

    @Override
    protected Boolean doInBackground(String... strings) {
        ...
        firebaseAuth.signInWithEmailAndPassword(email, password)
            .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        isSuccessful = task.isSuccessful();
                        isComplete = task.isComplete();
                        Log.v(TAG, "onComplete task is successful: " + isSuccessful);
                        Log.v(TAG, "onComplete task is complete: " + isComplete);
                        loginLock.unlock()
                    }
                })
                .addOnFailureListener(new OnFailureListener {
                    @Override
                    public void onFailure(Exception e) {
                        loginLock.unlock();
                    }
                });
        loginLock.lock();

        Log.v(TAG, "doInBackground() return type is " + (isSuccessful && isComplete));
        return isComplete && isSuccessful;
    }

    ...
}

Answered By - hluhovskyi