Application和Controller类之间的JavaFX FXML通信

Question

我试图通过我的FXML应用程序中的ProcessBuilder创建并销毁我创建的外部进程,但它无效.这是基于Sergey Grinev给我的有用建议.

我尝试使用/不使用"// myController.setApp(this);"运行 并使用"// super.stop();" 在子类的顶部和底部(请参阅MyApp中该行的注释/输入),但没有组合可行.

这可能与FXML或JavaFX无关,但我认为这是在JavaFX上开发应用程序的常见模式.我想我要求一个Java最佳实践来关闭基于UI的应用程序中的依赖进程(如本例所示:基于FXML/JavaFX),其中有一个控制器类和一个应用程序类.

你能解释一下我做错了什么吗？或者更好:建议我应该做什么呢？谢谢.

在我的应用程序中我这样做:

public class MyApp extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader fxmlLoader = new FXMLLoader();
        Scene scene = (Scene)FXMLLoader.load(getClass().getResource("MyApp.fxml"));
        MyAppController myController = (MyAppController)fxmlLoader.getController();

        primaryStage.setScene(scene);
        primaryStage.show();

//        myController.setApp(this);
    }

    @Override
    public void stop() throws Exception {
//      super.stop();

      // this is called on fx app close, you may call it in an action handler too
      if (MyAppController.getScriptProcess() != null) {
        MyAppController.getScriptProcess().destroy();
      }
      super.stop();
    }
    public static void main(String[] args) {
        launch(args);
    }
}

在我的控制器中,我这样做:

public class MyAppController implements Initializable {

  private Application app;
  private static Process scriptProcess;


  public void setApp(Application a) {
    app = a;
  }

  public static Process getScriptProcess() {
    return scriptProcess;
  }
}

当我使用未注释掉的"注释掉的setApp()" (即,在start方法中保留)运行时的结果如下,在启动后立即(主场景闪烁,然后消失,然后出现此对话框:

"JavaFX Launcher Error:
Exception while running Application"

它还在控制台中提供了"应用程序启动方法中的异常".

结果,当我离开了"注释掉的代码"在我MyApp的上方(也就是,从一开始的方法去除"setApp()"),是我的应用程序确实确实接近,但它关闭时给出了这样的错误:

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1440)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:28)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Node.fireEvent(Node.java:6863)
    at javafx.scene.control.Button.fire(Button.java:179)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:193)
    at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:336)
    at com.sun.javafx.scene.control.skin.SkinBase$4.handle(SkinBase.java:329)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:64)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
    at javafx.event.Event.fireEvent(Event.java:171)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3324)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3164)
    at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3119)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1559)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2261)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:228)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:528)
    at com.sun.glass.ui.View.notifyMouse(View.java:922)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication$3$1.run(GtkApplication.java:82)
    at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1435)
    ... 44 more
Caused by: java.lang.NullPointerException
    at mypackage.MyController.handleCancel(MyController.java:300)
    ... 49 more
Clean up...

Answer 1

方法是对的,但问题很少.

你已经创建了FXMLLoadernamed,fxmlLoader但是你调用的FXMLLoader.load()是静态方法,并且与之前创建的实例没有关联.

使用静态方法进行相互通信也不是很好(想象一下你会想要几个进程).更好地存储myController到字段并在stop()方法中调用它.

更好的方法是将相应的实用工具方法添加到Controller并从主应用程序中调用它,因为主应用程序似乎并没有使用Process它自己.

这里是简短的应用程序来演示所有描述:

public class DoTextAreaLog extends Application {

    private LoggController controller;

    @Override
    public void start(Stage stage) throws IOException{
            FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("logg.fxml"));
            VBox root = (VBox)fxmlLoader.load();
            controller = (LoggController) fxmlLoader.getController();

            stage.setScene(new Scene(root, 400, 300));
            stage.show();
    }

    @Override
    public void stop() throws Exception {
        super.stop();
        controller.destroy();
    }

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

控制器:

public class LoggController implements Initializable {

    @FXML private TextArea textarea;

    @FXML private void onAction(ActionEvent event) {
        destroy();
    }

    private Process p;

    public void destroy() {
        if (p != null) {
            p.destroy();
        }
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        try {
            p = new ProcessBuilder("ping", "stackoverflow.com", "-n", "100").start();

            new Thread(new Runnable() {
                @Override
                public void run() {
                    try {
                        try (BufferedReader bri = new BufferedReader(new InputStreamReader(p.getInputStream()))) {
                            String line;

                            while ((line = bri.readLine()) != null) {
                                log(line);
                            }
                        }
                    } catch (IOException ex) {
                        ex.printStackTrace();
                    }
                }
            }).start();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    private void log(final String st) {
        Platform.runLater(new Runnable() {
            @Override
            public void run() {
                textarea.setText(st + "\n" + textarea.getText());
            }
        });
    }
}

logg.fxml:

<VBox id="root" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml"  fx:controller="fxml.LoggController">
    <TextArea fx:id="textarea"/>
    <Button text="Stop The Madness!" onAction="#onAction"/>
</VBox>