Question

为什么这不起作用？我正在尝试将登录屏幕更改为示例屏幕。尝试使用连接到“提交”按钮的ActionEvent时出错。

引起：java.lang.NullPointerException：位置是必需的。

主：

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 {

    Stage stage;

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

    @Override
    public void start(Stage primaryStage) throws Exception{
        stage = primaryStage;

        Parent root = FXMLLoader.load(getClass().getResource("fxml/login.fxml"));
        stage.setTitle("Delos");

        Scene scene = new Scene(root, 300, 250);
        stage.setScene(scene);
        stage.show();
    }

}

控制器：

package controllers;

import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.stage.Stage;
import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;

public class Controller implements Initializable{


    //@FXML private TextField username;


    @FXML
    private void handleLogin(javafx.event.ActionEvent event) throws IOException {

        Parent blah = FXMLLoader.load(getClass().getResource("fxml/sample.fxml"));
        Scene scene = new Scene(blah);
        Stage appStage = (Stage) ((Node) event.getSource()).getScene().getWindow();
        appStage.setScene(scene);
        appStage.show();
    }

    /**public void handleLogin(ActionEvent actionEvent) {
        System.out.printf("You are logged in %s! %n", username.getText());
    }*/

    @Override
    public void initialize(URL location, ResourceBundle resources) {

    }
}

Login.fxml：

<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.text.Text?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.Pane?>

<GridPane fx:controller="controllers.Controller"
          stylesheets="/css/login.css"
          xmlns:fx="http://javafx.com/fxml">
    <children>
        <Text text="Sign In"
              styleClass="title"
              GridPane.rowIndex="0"
              GridPane.columnSpan="2"
              GridPane.halignment="CENTER"/>

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

        <TextField fx:id="username"
                   GridPane.rowIndex="1"
                   GridPane.columnIndex="1"/>

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

        <TextField fx:id="password"
                   GridPane.rowIndex="2"
                   GridPane.columnIndex="1"/>

        <Pane GridPane.rowIndex="3">
            <children>
                <Button text="Login"
                        onAction="#handleLogin"
                        GridPane.rowIndex="3"
                        GridPane.columnIndex="1"
                        GridPane.halignment="LEFT"/>
            </children>
        </Pane>
    </children>
</GridPane>

sampleController：

package controllers;

/**
 * Created by Basse on 22.11.2016.
 */

import javafx.fxml.Initializable;
import java.net.URL;
import java.util.ResourceBundle;

public class sampleController implements Initializable {

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        System.out.println("View is now loaded!");
    }
}

Sample.fxml：

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<VBox prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml"
      fx:controller="controllers.sampleController">

    <Label text="I love bacon"/>
    <Button text="Submit"/>

</VBox>

编辑：

/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/bin/java -Didea.launcher.port=7537 "-Didea.launcher.bin.path=/Applications/IntelliJ IDEA.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/lib/tools.jar:/Users/Basse/IdeaProjects/Delos/out/production/Delos:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar" com.intellij.rt.execution.application.AppMain Main
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
    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.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:8411)
    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.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$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:416)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
    ... 45 more
Caused by: java.lang.NullPointerException: Location is required.
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
    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 controllers.Controller.handleLogin(Controller.java:24)
    ... 55 more

JavaFX：改变阶段

0 个答案: