尝试使用＆＃34; pimaryStage＆＃34;时，JavaFX崩溃

Question

我只是在学习JavaFX而且我正在尝试创建一个自定义标题栏，你可以像普通的那样移动，但是我没有使用移动代码本身，而是操纵窗口。

我正在使用 FXML 来管理布局BTW。

这是我的代码：

主要课程

public class Main extends Application {

    public Stage mainStage;
    @FXML
    Parent root;

    @Override
    public void start(Stage primaryStage) {
        this.mainStage = primaryStage;
        try {
            root = FXMLLoader.load(getClass().getResource("Main.fxml"));
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }

        Scene scene = new Scene(root);

        scene.getStylesheets().add(getClass().getResource("Main.css").toString());
        mainStage.initStyle(StageStyle.TRANSPARENT);
        mainStage.setScene(scene);
        mainStage.sizeToScene();
        mainStage.show();
    }

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

控制器类

public class MainController {
    @FXML
    Parent root;

    double startX;
    double startY;

    public void exit() {
        System.exit(0);
    }

    @FXML
    public void mousePressed(MouseEvent e) {
        System.out.println("Initial:" + e.getX() + "," + e.getY()); //Debug code
        startX = e.getSceneX();
        startY = e.getSceneY();
    }

    @FXML
    public void mouseDragged(MouseEvent e) {
        System.out.println("Dragged:" + (e.getScreenX() - startX) + "," + (e.getScreenY() - startY)); //Debug code
        if (e.getButton() == MouseButton.PRIMARY) {
            Stage stage = (Stage) root.getScene().getWindow();
            stage.setX(e.getScreenX() - startX);
            stage.setY(e.getScreenY() - startY);
        }
    }
}

FXML

<fx:root prefHeight="633.0" prefWidth="1071.0" type="javafx.scene.layout.AnchorPane" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.franga2000.launcher.MainController">
   <children>
      <Pane onMouseDragged="#mouseDragged" onMousePressed="#mousePressed" prefHeight="43.0" prefWidth="1071.0" styleClass="titlebar" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
         <children>
            <Button layoutX="1019.0" layoutY="9.0" onMouseClicked="#exit" text="Quit" />
         </children>
      </Pane>
   </children>
</fx:root>

即使我尝试修改mainStage方法之外的主类中的start()，我总是会遇到同样的崩溃：

Thread [JavaFX Application Thread] (Suspended (exception RuntimeException)) 
    GlassViewEventHandler$MouseEventNotification.run() line: not available [local variables unavailable]    
    GlassViewEventHandler$MouseEventNotification.run() line: not available  
    AccessController.doPrivileged(PrivilegedAction<T>, AccessControlContext) line: not available [native method]    
    GlassViewEventHandler.handleMouseEvent(View, long, int, int, int, int, int, int, int, int, boolean, boolean) line: not available    
    WinView(View).handleMouseEvent(long, int, int, int, int, int, int, int, int, boolean, boolean) line: not available  
    WinView(View).notifyMouse(int, int, int, int, int, int, int, boolean, boolean) line: not available  
    WinApplication._runLoop(String[], Launchable) line: not available [native method]   
    WinApplication.access$100(WinApplication, String[], Launchable) line: not available 
    WinApplication$3$1.run() line: not available    
    Thread.run() line: not available