如何在具有自定义元素的Scene Builder中打开fxml？

Question

根据我在此question中收到的答案，我在TextFields文件中将所有TextFieldPasteListener替换为fxml。问题是，我无法再在Scene Builder中打开fxml。这是我得到的错误：

java.io.IOException: javafx.fxml.LoadException:
/C:/Users/aljona.gvozdeva/Documents/workspace/AccountingApp/src/home/accounting/view/RegistrationForm.fxml
    at com.oracle.javafx.scenebuilder.kit.fxom.FXOMLoader.load(FXOMLoader.java:92)
    at com.oracle.javafx.scenebuilder.kit.fxom.FXOMDocument.<init>(FXOMDocument.java:82)
    at com.oracle.javafx.scenebuilder.kit.fxom.FXOMDocument.<init>(FXOMDocument.java:97)
    at com.oracle.javafx.scenebuilder.kit.editor.EditorController.updateFxomDocument(EditorController.java:2384)
    at com.oracle.javafx.scenebuilder.kit.editor.EditorController.setFxmlTextAndLocation(EditorController.java:664)
    at com.oracle.javafx.scenebuilder.app.DocumentWindowController.loadFromFile(DocumentWindowController.java:385)
    at com.oracle.javafx.scenebuilder.app.SceneBuilderApp.performOpenFiles(SceneBuilderApp.java:634)
    at com.oracle.javafx.scenebuilder.app.SceneBuilderApp.access$200(SceneBuilderApp.java:84)
    at com.oracle.javafx.scenebuilder.app.SceneBuilderApp$1.invalidated(SceneBuilderApp.java:496)
    at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:137)
    at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
    at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
    at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:103)
    at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
    at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:144)
    at com.oracle.javafx.scenebuilder.kit.library.user.UserLibrary.lambda$updateFirstExplorationCompleted$7(UserLibrary.java:324)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: 
/C:/Users/aljona.gvozdeva/Documents/workspace/AccountingApp/src/home/accounting/view/RegistrationForm.fxml

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
    at javafx.fxml.FXMLLoader.importClass(FXMLLoader.java:2848)
    at javafx.fxml.FXMLLoader.processImport(FXMLLoader.java:2692)
    at javafx.fxml.FXMLLoader.processProcessingInstruction(FXMLLoader.java:2661)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2517)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2425)
    at com.oracle.javafx.scenebuilder.kit.fxom.FXOMLoader.load(FXOMLoader.java:89)
    ... 22 more
Caused by: java.lang.ClassNotFoundException: home.accounting.controller.TextFieldPasteListener
    at java.lang.ClassLoader.findClass(ClassLoader.java:530)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at javafx.fxml.FXMLLoader.loadTypeForPackage(FXMLLoader.java:2916)
    at javafx.fxml.FXMLLoader.loadType(FXMLLoader.java:2905)
    at javafx.fxml.FXMLLoader.importClass(FXMLLoader.java:2846)
    ... 27 more

我在TextFieldPasteListener文件中导入了fxml：

<?import home.accounting.controller.TextFieldPasteListener?>

这是我的TextFieldPasteListener课程：

import com.sun.glass.events.KeyEvent;
import com.sun.glass.ui.Robot;

import javafx.scene.control.TextField;

@SuppressWarnings("restriction")
public class TextFieldPasteListener extends TextField {
    @Override
   public void paste() {
       super.paste();
       try {
           Robot robot = com.sun.glass.ui.Application.GetApplication().createRobot();
           robot.keyPress(KeyEvent.VK_ENTER);
       } catch (Exception e) {
           e.printStackTrace();
       }
   }
}

在添加自定义元素后，有什么方法可以使用Scene Builder编辑fxml吗？