private TextInputLayout mName;
private TextInputLayout mEmail;
private TextInputLayout mPwd;
private Button mSubmit;
String username, email,password;
private FirebaseAuth mAuth;

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

    mAuth = FirebaseAuth.getInstance();

    mName=(TextInputLayout)findViewById(R.id.pName);
    mEmail=(TextInputLayout)findViewById(R.id.pEmail);
    mPwd=(TextInputLayout)findViewById(R.id.pPassword);
    mSubmit=(Button) findViewById(R.id.regStart);

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

            username= mName.getEditText().getText().toString();
            email= mEmail.getEditText().getText().toString();
            password= mPwd.getEditText().getText().toString();

            Toast.makeText(getApplicationContext(), username+" "+email+" "+password,
                    Toast.LENGTH_SHORT).show();
            register_user(username,email,password);

        }
    });

}

private void register_user(String username, String email, String password)
{

    mAuth.createUserWithEmailAndPassword(email, password)
            .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("yaaayy", "createUserWithEmail:success");

                        Intent i= new Intent(getApplicationContext(),MainActivity.class);
                        startActivity(i);
                        finish();

                    } else {
                        // If sign in fails, display a message to the user.
                        Log.w("oops", "createUserWithEmail:failure", task.getException());
                        Toast.makeText(getApplicationContext(), "Authentication failed.",
                                Toast.LENGTH_SHORT).show();

                    }

                    // ...
                }
            });
} }