JavaFX. Как добавить текст в TextArea из дочернего класса?

Рейтинг: 0Ответов: 1Опубликовано: 15.05.2023

Есть проект с использованием фреймворка JavaFX, если свести все к минимально воспроизводимому примеру, то выглядит он так:

Main.java

package main;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("/fxml/main.fxml"));
        primaryStage.setScene(new Scene(root, 600, 400));
        primaryStage.show();
    }
    
    public static void main(String[] args)  {
        launch(args);
    }
    
}

main.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextArea?>
<?import javafx.scene.layout.VBox?>

<VBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/19" xmlns:fx="http://javafx.com/fxml/1" fx:controller="main.Controller">
   <children>
      <TextArea fx:id="textArea" editable="false" prefHeight="406.0" prefWidth="600.0" />
      <Button fx:id="button" maxWidth="1.7976931348623157E308" mnemonicParsing="false" onAction="#buttonPressed" prefHeight="26.0" text="Button" />
   </children>
</VBox>

Controller.java

package main;

import java.io.IOException;

import javafx.scene.control.Button;
import javafx.scene.control.TextArea;

public class Controller {
    
    public TextArea textArea;
    public Button button;
    
    public void buttonPressed() throws IOException {
        System.out.println("Button Pressed");
        
        Scan myObj = new Scan();
        myObj.run();
        
    }
    
}

Scan.java

package main;

import java.io.IOException;

public class Scan extends Controller {
    
    public void run() throws IOException {
        
        System.out.println("Scan...");
        
        this.textArea.appendText("Append text to TextArea" + "\n");
        
    }

}

При нажатии на кнопку с fx:id button вызывается действие buttonPressed, в котором создается экземпляр класса Scan (наследуется от Controller) и вызывается метод run. Он в свою очередь должен добавлять текст в элемент TextArea с fx:id textArea:

this.textArea.appendText("Append text to TextArea" + "\n");

Вроде все логично, только вместо желаемого результата я ловлю InvocationTargetException...

Что я делаю не так?

UPD: Привожу полную версию исключения, только вот все равно ничего не понятно...Копаюсь в исходниках JavaFX, пытаюсь разобраться...

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml@20/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1858)
    at javafx.fxml@20/javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1726)
    at javafx.base@20/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at javafx.base@20/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:232)
    at javafx.base@20/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:189)
    at javafx.base@20/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base@20/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base@20/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base@20/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base@20/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base@20/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base@20/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base@20/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base@20/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.base@20/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics@20/javafx.scene.Node.fireEvent(Node.java:8944)
    at javafx.controls@20/javafx.scene.control.Button.fire(Button.java:203)
    at javafx.controls@20/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:207)
    at javafx.controls@20/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
    at javafx.base@20/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
    at javafx.base@20/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at javafx.base@20/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:232)
    at javafx.base@20/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:189)
    at javafx.base@20/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base@20/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base@20/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base@20/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base@20/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base@20/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base@20/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base@20/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base@20/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.base@20/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics@20/javafx.scene.Scene$MouseHandler.process(Scene.java:3980)
    at javafx.graphics@20/javafx.scene.Scene.processMouseEvent(Scene.java:1890)
    at javafx.graphics@20/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2704)
    at javafx.graphics@20/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:411)
    at javafx.graphics@20/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:301)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
    at javafx.graphics@20/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:450)
    at javafx.graphics@20/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
    at javafx.graphics@20/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:449)
    at javafx.graphics@20/com.sun.glass.ui.View.handleMouseEvent(View.java:551)
    at javafx.graphics@20/com.sun.glass.ui.View.notifyMouse(View.java:937)
    at javafx.graphics@20/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics@20/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:185)
    at java.base/java.lang.Thread.run(Thread.java:1623)
Caused by: java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:116)
    at java.base/java.lang.reflect.Method.invoke(Method.java:578)
    at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:72)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
    at java.base/java.lang.reflect.Method.invoke(Method.java:578)
    at javafx.base@20/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:270)
    at javafx.fxml@20/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:84)
    at javafx.fxml@20/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1855)
    ... 46 more
Caused by: java.lang.NullPointerException: Cannot invoke "javafx.scene.control.TextArea.appendText(String)" because "this.textArea" is null
    at MeinPortScanner/main.Scan.run(Scan.java:14)
    at MeinPortScanner/main.Controller.buttonPressed(Controller.java:23)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
    ... 53 more

Ответы

▲ 0Принят

Я понял в чем cоcтоит проблема. Вcе дело в том, что при иcпользовании FXML для поcтроения пользовательcких интерфейcов к его виджетам можно обращатьcя только непоcредcтвенно из cамого контролера. Немного изменил проект и вcе работает.