MainActivity Java code

MainActivity.java

package com.gkquizadmin;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;

public class MainActivity extends AppCompatActivity {

    private EditText email, password;
    private ProgressBar progressBar;
    private FirebaseAuth firebaseAuth;

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

        email = findViewById(R.id.email);
        password = findViewById(R.id.password);
        Button login = findViewById(R.id.login);
        progressBar = findViewById(R.id.progressBar);

        firebaseAuth = FirebaseAuth.getInstance();

        if (firebaseAuth.getCurrentUser() != null) {
            //intent
            return;
        }

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (email.getText().toString().isEmpty()) {
                    email.setError("required!!");
                    return;
                } else {
                    email.setError(null);
                }

                if (password.getText().toString().isEmpty()) {
                    password.setError("required!!");
                    return;
                } else {
                    password.setError(null);
                }

                progressBar.setVisibility(View.VISIBLE);

                firebaseAuth.signInWithEmailAndPassword(email.getText().toString(), password.getText().toString()).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            Toast.makeText(MainActivity.this, "Success", Toast.LENGTH_SHORT).show();
                        } else {
                            Toast.makeText(MainActivity.this, task.getException().toString(), Toast.LENGTH_SHORT).show();
//                            Toast.makeText(MainActivity.this, "Failed", Toast.LENGTH_SHORT).show();
                        }

                        progressBar.setVisibility(View.INVISIBLE);

                    }
                });
            }
        });
    }
}