JavaFX getScene（）在控制器的initialize方法中返回null

Question

我昨天在JavaFX中构建了一个小应用程序。我想在Controller类中获取应用程序的场景。每次我试图在控制器类中获取场景时，我都会出错。我可以在Controller类中的Button上设置OnKeyPested-method，工作正常。但是只有当按钮被选中时，它才工作正常...我可以只在Main类方法replace eSceneContent中获取场景。我已经读过这个问题了，但是我在初始化方法中调用getScene（）-方法？？感谢任何想法！

主要类别：

public class Main extends Application {

private Stage stage;

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

@Override
public void start(Stage primaryStage) throws Exception {
    stage = primaryStage;
    gotoMenu();
    primaryStage.show();
}

public void gotoMenu() {
    try {
        MenuController menu = new MenuController();
        menu = (MenuController) replaceSceneContent("Menu.fxml");
        menu.setApp(this);
    } catch (Exception ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
    }
}

private Node replaceSceneContent(String fxml) throws Exception {
    FXMLLoader loader = new FXMLLoader();
    @SuppressWarnings("resource")
    InputStream in = Main.class.getResourceAsStream(fxml);
    loader.setBuilderFactory(new JavaFXBuilderFactory());
    loader.setLocation(Main.class.getResource(fxml));
    BorderPane page;
    try {
        page = (BorderPane) loader.load(in);
    } finally {
        in.close();
    }
    page.setOnKeyPressed(event -> {
        switch (event.getCode()) {
        case F11:
            if (stage.isFullScreen()) {
                stage.setFullScreen(false);
            } else {
                stage.setFullScreen(true);
            }
            break;
        default:
            break;
        }
    });
    Scene scene = new Scene(page);
    page.prefWidthProperty().bind(scene.widthProperty());
    page.prefHeightProperty().bind(scene.heightProperty());
    stage.setScene(scene);
    return (Node) loader.getController();
}}

控制器类：

public class MenuController extends BorderPane implements Initializable {

Main application;

@FXML
private Button button;

public void setApp (Main application) {
    this.application = application;
}

@Override
public void initialize(URL location, ResourceBundle resources) {
    button.getScene().setOnKeyPressed(e -> {
        switch(e.getCode()) {
        case A:
            System.out.println("A pressed!");
            break;
        default:
            break;
        }
    });
}}}

Answer 1

这是我应用程序的1.1版。我在setOnKeyPressed事件处理程序中添加了一个if子句。控制器初始化完成后，一个方法将布尔控制器运行设置为true。最后我删除了InputStream，它不需要了。

如果有人需要一个例子：

主要类别：

public class Main extends Application {

private Stage stage;
private boolean controllerRunning = false;
MenuController menu;

public void setControllerRunning(boolean controllerRunning) {
    this.controllerRunning = controllerRunning;
}

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

@Override
public void start(Stage primaryStage) throws Exception {
    stage = primaryStage;
    gotoMenu();
    primaryStage.show();
}

public void gotoMenu() {
    try {
        menu = new MenuController();
        menu = (MenuController) replaceSceneContent("Menu.fxml");
        menu.setApp(this);
        menu.keyFunctions();
    } catch (Exception ex) {
        Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
    }
}

private Node replaceSceneContent(String fxml) throws Exception {
    FXMLLoader loader = new FXMLLoader();
    loader.setBuilderFactory(new JavaFXBuilderFactory());
    loader.setLocation(Main.class.getResource(fxml));
    BorderPane page;
    try {
        page = (BorderPane) loader.load();
    } finally {
    }
    page.setOnKeyPressed(event -> {
        if (controllerRunning) {
            switch (event.getCode()) {
            case A:
                menu.printA();
                break;
            default:
                break;
            }
        }
        switch (event.getCode()) {
        case F11:
            if (stage.isFullScreen()) {
                stage.setFullScreen(false);
            } else {
                stage.setFullScreen(true);
            }
            break;
        default:
            break;
        }
    });
    Scene scene = new Scene(page);
    page.prefWidthProperty().bind(scene.widthProperty());
    page.prefHeightProperty().bind(scene.heightProperty());
    stage.setScene(scene);
    return (Node) loader.getController();
}}

控制器类：

public class MenuController extends BorderPane{

Main application;

@FXML
private Button button;

public void setApp (Main application) {
    this.application = application;
}

public void keyFunctions() {
    application.setControllerRunning(true);
}
public void printA() {
    System.out.println("A!");
}
}

Answer 2

你能做到的

private Node replaceSceneContent(String fxml) throws Exception {
    FXMLLoader loader = new FXMLLoader();
    loader.setBuilderFactory(new JavaFXBuilderFactory());
    loader.setLocation(Main.class.getResource(fxml));

    BorderPane page = loader.load();
    MenuController controller = loader.getController();

    page.setOnKeyPressed(event -> {
        switch (event.getCode()) {
        case F11:
            if (stage.isFullScreen()) {
                stage.setFullScreen(false);
            } else {
                stage.setFullScreen(true);
            }
            break;
        default:
            break;
        }
    });
    Scene scene = new Scene(page);
    scene.setOnKeyPressed(event -> {
        if (event.getCode() == KeyCode.A) {
            controller.printA();
        }
    });


    page.prefWidthProperty().bind(scene.widthProperty());
    page.prefHeightProperty().bind(scene.heightProperty());
    stage.setScene(scene);
    return controller ;
}

具有

public class MenuController extends BorderPane{

    // existing code...

    public void printA() {
        System.out.println("A!");
    }

}

只是一个注释：MenuController作为BorderPane（或任何其他UI类）的子类是毫无意义的。我留了下来，以防你在其他地方需要它，但它完全违反了MVC模式。

此外，我不太清楚为什么你希望A的密钥处理程序出现在场景中，而F11的密钥处理程序出现在场景的根目录中。看来这两个都应该在现场登记。但我还是把问题留给了你。