Firebase Authentication

SignupActivity.java

signupBtn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {

        String userEmail = signupEmail.getText().toString();
        String userPasword = signupPassword.getText().toString();

        if (userEmail.isEmpty()) {
            signupEmail.setError("Email Cannot be Empty");
        }
        if (userPasword.isEmpty()) {
            signupPassword.setError("Password Cannot be Empty");
        } else {
            auth.createUserWithEmailAndPassword(userEmail, userPasword).addOnCompleteListener(new OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {

                    if (task.isSuccessful()) {
                        Toast.makeText(FirebaseSignupActivity.this, "Signup Successfull", Toast.LENGTH_SHORT).show();
                        Intent intent = new Intent(FirebaseSignupActivity.this, MainActivity.class);
                        startActivity(intent);

                    } else {
                        Toast.makeText(FirebaseSignupActivity.this, "Signup Fail: " + task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                    }
                }
            });
        }
    }
});

LoginActivity.java

loginBtn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {

        String userEmail = loginEmail.getText().toString();
        String userPassword = loginPassword.getText().toString();

        if (userEmail.isEmpty()) {
            loginEmail.setError(("Email Cannot be Empty"));
        }
        if (userPassword.isEmpty()) {
            loginPassword.setError(("Password Cannot be Empty"));
        } else {
            auth.signInWithEmailAndPassword(userEmail, userPassword).addOnSuccessListener(new OnSuccessListener<AuthResult>() {
                @Override
                public void onSuccess(AuthResult authResult) {
                    Toast.makeText(FirebaseLoginActivity.this, "Login Successful", Toast.LENGTH_SHORT).show();
                    Intent intent = new Intent(FirebaseLoginActivity.this, MainActivity.class);
                    startActivity(intent);
                }
            }).addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    Toast.makeText(FirebaseLoginActivity.this, "Login Failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
                }
            });
        }
    }
});