事件调用时出现 javafx 错误答案

【问题标题】：javafx error when event invokes事件调用时出现 javafx 错误
【发布时间】：2015-11-16 16:19:10
【问题描述】：

我是 javafx 的新手，刚开始在按钮上调用事件时遇到了一堆错误。我在带有 jdk1.8 的 NetBeans 8.1 中使用 SceneBuilder 2.0。我在场景构建器中创建了基本布局

我在我的控制器类中创建了一个简单的方法，它只从 textField 获取文本并将其设置到 textArea 中。我把它设置在一个按钮上。程序运行和构建都很好，但是当我单击按钮时出现错误。

这是我的代码：

package javafxapp;
import java.net.URL;
import java.lang.*;
import java.util.*;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
public class FXMLDocumentController implements Initializable {

@FXML
private TextField chatText;
@FXML
private TextArea chatArea;
@FXML
private void handleButtonAction(ActionEvent event) {
    System.out.println("You clicked me!");

}

@Override
public void initialize(URL url, ResourceBundle rb) {
    // TODO
}    

public void sendMsg(ActionEvent action)
{
chatArea.setText(chatText.getText());
chatText.setText("");
}

}

这是我的主要课程：

package javafxapp;

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


public class JavaFXApp extends Application {

@Override
public void start(Stage stage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("/fxml/FXMLDocument.fxml"));

    Scene scene = new Scene(root);

    stage.setScene(scene);
    stage.show();
}


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

}

现在是错误：

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
	at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1762)
	at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1645)
	at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
	at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
	at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
	at javafx.event.Event.fireEvent(Event.java:198)
	at javafx.scene.Node.fireEvent(Node.java:8216)
	at javafx.scene.control.Button.fire(Button.java:185)
	at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
	at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
	at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
	at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
	at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
	at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
	at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
	at javafx.event.Event.fireEvent(Event.java:198)
	at javafx.scene.Scene$MouseHandler.process(Scene.java:3724)
	at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3452)
	at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1728)
	at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2461)
	at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:348)
	at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:273)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:382)
	at com.sun.glass.ui.View.handleMouseEvent(View.java:553)
	at com.sun.glass.ui.View.notifyMouse(View.java:925)
	at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
	at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102)
	at com.sun.glass.ui.win.WinApplication$$Lambda$37/1147985808.run(Unknown Source)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
	at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1757)
	... 63 more
Caused by: java.lang.NullPointerException
	at javafxapp.FXMLDocumentController.sendMsg(FXMLDocumentController.java:40)
	... 73 more

我不知道是什么导致了错误，但是“handleButtonAction”方法工作正常。 “如果我提出的问题是错误的，请道歉，我以前从未在这里问过任何问题”

【问题讨论】：

您能发布您的 FXML 文档吗？检查您的 chatText 和 chatArea 是否正确连接到 FXML。
是的，错误在于连接元素，发布后我再次检查代码，发现场景构建器中的“fx:id”为空白。我之前没有检查它，因为它应该是自动连接的，所以我手动填充它。可能是软件问题。无论如何感谢您的快速回复:)
太棒了。我添加了答案，所以可能有相同问题的其他人可以看到它。
另外，我在将代码从场景构建器连接到 IDE 时遇到了问题。就像我刚刚将我的方法从“handleButtonAction”更改为“sendMsg”但它仍然停留在第一个，我已经从场景构建器和 IDE 中更改了它，我保存了它并清理了它但仍然相同。我不得不关闭这两个程序并再次运行它。我应该改变我的IDE吗？
如果您将更改保存在那里，我不知道 Scenebuilder 会做什么，因为我不使用它。但我不认为 Netbeans 应该有问题。

标签： javafx scenebuilder

【解决方案1】：

您的元素可能未正确连接到 FXML。检查 chatArea 和 chatText 是否在您的 FXML 中设置为 fx:id。

【讨论】：

【解决方案2】：

好的。所以我知道有两种不同的方法可以解决这个问题。

技术 1) 要按照你已经在做的方式来做，试试这个：

@FXML
    private void handleButtonAction(javafx.event.ActionEvent event) throws IOException
{//etc...}

技术2）您也可以创建一个普通方法，然后从场景构建器中调用它，如下所示：

public void handleButtonAction()
{
      //your code goes here
}

现在，进入场景生成器，单击按钮，导航到侧面板的“代码”部分，然后查找“动作中”。在“On Action”中，输入您的方法的名称，不带括号。因此，在这种情况下，您只需键入“handleButtonAction”。保存文档。

它现在应该可以工作了。

第二种是我在这种情况下推荐的技术。它只是更干净，更好看。

如果这有帮助，请告诉我：)

【讨论】：