Oracle 的 javaFX 教程中的 FXMLLoader 问题

Question

前段时间我从 Oracle 网站开始学习 javafx 教程。在学习本教程的过程中 https://docs.oracle.com/javase/8/javafx/get-started-tutorial/fxml_tutorial.htm 我遇到了一个问题。这是一个代码：

1) fxml_example.fxml

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

<?import java.net.*?>
<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.text.*?>

<GridPane fx:controller="fxmlexample.FXMLExampleController"
xmlns:fx="http://javafx.com/fxml" alignment="center" hgap="10" vgap="10">
<fx:script>
    function handleSubmitButtonAction(){
    actiontarget.setText("Calling the JavaScript");
    }
</fx:script>
<padding>
    <Insets top="25" right="25" bottom="10" left="25" />
</padding>

<Text text="Welcome" GridPane.columnIndex="0"
    GridPane.columnSpan="2" GridPane.rowIndex="0" />

<Label text="User Name:" GridPane.columnIndex="0"
    GridPane.rowIndex="1" />

<TextField GridPane.columnIndex="1" GridPane.rowIndex="1" />

<Label text="Password:" GridPane.columnIndex="0"
    GridPane.rowIndex="2" />

<PasswordField fx:id="passwordField"
    GridPane.columnIndex="1" GridPane.rowIndex="2" />

<HBox alignment="bottom_right" spacing="10"
    GridPane.columnIndex="1" GridPane.rowIndex="4">

    <Button text="Button" onAction="#handleSubmitButtonAction" />

</HBox>

<Text fx:id="actiontarget" GridPane.columnIndex="0"
    GridPane.columnSpan="2" GridPane.halignment="RIGHT"
    GridPane.rowIndex="6" />
</GridPane>

2) FXMLExample.java

package application;

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

public class FXMLExample extends Application{
    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("fxml_example.fxml"));

    Scene scene = new Scene(root, 300, 275);

    stage.setTitle("FXML Welcome");
    stage.setScene(scene);
    stage.show();
    }

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

3) FXMLExampleController.java

package application;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.text.Text;

public class FXMLExampleController {
    @FXML private Text actiontarget;

    @FXML protected void handleSubmitButtonAction(ActionEvent event) {
        actiontarget.setText("Sign in button pressed");
    }
}

这里是例外列表：

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at         com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.launcher.LauncherHelper$FXHelper.main(Unknown Source)
Caused by: java.lang.RuntimeException: Exception in Application start method
at     com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication4(LauncherImpl.java:182)
at java.lang.Thread.run(Unknown Source)
Caused by: javafx.fxml.LoadException: 
/C:/Users/.../eclipse-workspace/FXMLExample/bin/application    /fxml_example.fxml:10

at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
at javafx.fxml.FXMLLoader.access0(FXMLLoader.java:103)
at     javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:922)
at     javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.    java:971)
at javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:220)
at javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:744)
at javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2707)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2527)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at application.FXMLExample.start(FXMLExample.java:12)
at     com.sun.javafx.application.LauncherImpl.lambda$launchApplication11(Launcher    Impl.java:863)
at     com.sun.javafx.application.PlatformImpl.lambda$runAndWait4(PlatformImpl.jav    a:326)
at com.sun.javafx.application.PlatformImpl.lambda$null2(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater3(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null7(WinApplication.java:177)
... 1 more
Caused by: java.lang.ClassNotFoundException:     fxmlexample.FXMLExampleController
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at     javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:920)
... 22 more
Exception running application application.FXMLExample

那么，FXMLLoader 有问题吗？但是什么？以及如何修复它？

Answer 1

您的 FXML 将 fx:controller 设置为 fxmlexample.FXMLExampleController，但您的包名称是 application，因此 fx:controller 值应该是 application.FXMLExampleController（或者您可以将您的包名称更改为 fxmlexample 以匹配示例代码）。

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