在JavaFX中最大化启动应用程序窗口FXML不能正常工作

<AnchorPane fx:controller="com.example.MainController" xmlns:fx="http://javafx.com/fxml">
    <children>
        <!-- 窗口内容 -->
    </children>
    <fx:define>
        <Stage fx:id="mainStage" width="800" height="600" title="My Application" />
    </fx:define>
    <fx:scene>
        <Scene>
            <!-- 窗口场景内容 -->
        </Scene>
    </fx:scene>
</AnchorPane>

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("main.fxml"));
        Parent root = loader.load();
        primaryStage.setTitle("My Application");
        primaryStage.setScene(new Scene(root, 800, 600));
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

public class MainController implements Initializable {
    @FXML
    private Stage mainStage;

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        // 初始化操作
    }

    @FXML
    private void handleMaximizeButtonAction(ActionEvent event) {
        mainStage.setMaximized(true);
    }
}