private void initFirebase() {
 firebaseAuth = FirebaseAuth.getInstance();
}
private void goToHome() {
 Intent intent = new Intent(this, home.class);
 intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
 startActivity(intent);
}
@OnClick({R.id.button_login_activity_main, R.id.button_sign_up_activity_main})
public void onClick(Button button) {
 switch (button.getId()) {
 case R.id.button_login_activity_main:
 String username = editTextUsername.getText().toString().trim();
 String password = editTextPassword.getText().toString().trim();
 login(username, password);
 break;
 case R.id.button_sign_up_activity_main:
 // go to form pendaftaran
 startActivity(new Intent(this, SignupActivity.class));
 break;
 }
}
private void login(final String username, final String password) {
 if (TextUtils.isEmpty(username)) {
 Snackbar.make(findViewById(android.R.id.content), R.string.error_message_username_empty, Snackbar.LENGTH_LONG)
 .show();
 } else if (TextUtils.isEmpty(password)) {
 Snackbar.make(findViewById(android.R.id.content), R.string.error_message_password_empty, Snackbar.LENGTH_LONG)
 .show();
 } else {
 // do login
 showProgress();
 firebaseAuth.signInWithEmailAndPassword(username, password)
 .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
 @Override
 public void onComplete(@NonNull Task<AuthResult> task) {
 hideProgress();
 if (task.isSuccessful()) {
 // login sucess
 // go to dashboard
 goToHome();
 } else {
 // login failed
 showMessageBox("Login failed. Your username and password is not matched");
 }
 }
 });
 }
}
private void hideProgress() {
 relativeLayoutProgress.setVisibility(View.GONE);
 editTextUsername.setEnabled(true);
 editTextPassword.setEnabled(true);
}
private void showProgress() {
 relativeLayoutProgress.setVisibility(View.VISIBLE);
 editTextUsername.setEnabled(false);
 editTextPassword.setEnabled(false);
}
private void showMessageBox(String message) {
 AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
 alertDialogBuilder.setTitle("Login");
 alertDialogBuilder.setMessage(message);
 alertDialogBuilder.setCancelable(false);
 alertDialogBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
 @Override
 public void onClick(DialogInterface dialogInterface, int i) {
 dialogInterface.dismiss();
 }
 });
 alertDialogBuilder.show();
}
public boolean isLoggedIn() {
 if (firebaseAuth.getCurrentUser() != null) {
 // user logged in
 return true;
 } else {
 return false;
 }
}