public class Login extends AppCompatActivity {

    EditText usuario, senha;
    FrameLayout framePB;

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

        this.usuario = findViewById(R.id.edittextUsuario);
        this.senha = findViewById(R.id.edittextSenha);
        this.framePB = findViewById(R.id.framelayoutProgressBar);
    }

    public void buttonLogin(View view) {

        AsyncLogin login = new AsyncLogin(this.framePB, this.usuario.toString, this.senha.toString);
        login.execute();
}

public class AsyncLogin extends AsyncTask<String, String, String> {

    String usuario, senha;
    FrameLayout framePB;

    public AsyncLogin(FrameLayout framePB, String usuario, String senha) {

        this.framePB = framePB;
        this.usuario = usuario;
        this.senha = senha;
    }

    ...

}

public class Login extends AppCompatActivity {

    public void buttonLogin(View view) {

        String retorno = "";

        AsyncLogin login = new AsyncLogin(this.framePB, this.usuario.toString, this.senha.toString);
        login.execute();

        try {
            retorno = login.get();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

        Toast.makeText(this, retorno, Toast.LENGTH_SHORT).show();
    }

}