参见英文答案 > What is a NullPointerException, and how do I fix it?                                    12个
这是我的主类

package application;

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

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        try {
            Parent root = FXMLLoader.load(getClass().getResource("application/anwendung.fxml"));
            primaryStage.setTitle("Benutzerverwaltung");
            root.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
            primaryStage.setScene(new Scene(root));
            primaryStage.show();
        } catch(Exception e) {
            e.printStackTrace();
        }
    }

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

这是我的Controller类

package application;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.Node;
import javafx.scene.control.Button;
import javafx.scene.input.InputEvent;
import javafx.stage.Stage;

class AnwendungsController {

    @FXML
    public Button closeButton;


    @FXML
    public void handleCloseButtonAction(ActionEvent event) {
        Stage stage = (Stage) closeButton.getScene().getWindow();
        stage.close();
    }
}

这是我的fxml文件

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>

<AnchorPane prefHeight="140.0" prefWidth="350.0"     xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1"     fx:controller="application.AnwendungsController">
  <children>
   <Button fx:id="closeButton" layoutX="18.0" layoutY="100.0" mnemonicParsing="false" onAction="#handleCloseButtonAction" onm ouseClicked="#onMouseClickedCancelBtn" prefHeight="26.0" prefWidth="77.0"  text="Abbrechen" />
   <Label layoutX="10.0" layoutY="27.0" prefHeight="27.0" prefWidth="342.0" text="Sie können das System nun verwenden" textAlignment="CENTER" textOverrun="CLIP">
     <font>
        <Font name="System Bold" size="18.0" />
     </font>
  </Label>
   </children>
  </AnchorPane>

我该如何解决？我从这里尝试一切JavaFX “Location is required.” even though it is in the same package

更新：

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 application.Main.start(Main.java:20)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$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(Unknown Source)

解决方法:

存在两个问题：

1)文件路径

2)控制器设置不正确

Reccomendation：

如果您正在使用SceneBuilder,当您想要查看控制器的方式时,您可以进入View – >显示样本控制器骨架 – >复制 – >粘贴 – >享受生活(直到下一个错误发生：||)

>解决方案

主要课程：

package application;

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

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        try {
            System.out.println(getClass().getResource("anwendung.fxml").getPath());

            //other solution
            //FXMLLoader loader = new FXMLLoader(getClass().getResource("anwendung.fxml"));
            //Parent root = loader.load();

            //Keep in mind that you are calling a static method
            Parent root = FXMLLoader.load(getClass().getResource("anwendung.fxml"));

            primaryStage.setTitle("Benutzerverwaltung");
            root.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
            primaryStage.setScene(new Scene(root));
            primaryStage.show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

控制器：

package application;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.input.MouseEvent;

public class AnwendungsController {

    @FXML
    private Button closeButton;

    @FXML
    void handleCloseButtonAction(ActionEvent event) {

    }

    @FXML
    void onm ouseClickedCancelBtn(MouseEvent event) {

    }

}

FXML：

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>

<AnchorPane prefHeight="140.0" prefWidth="350.0" xmlns="http://javafx.com/javafx/8.0.60" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.AnwendungsController">
  <children>
   <Button fx:id="closeButton" layoutX="18.0" layoutY="100.0" mnemonicParsing="false" onAction="#handleCloseButtonAction" onm ouseClicked="#onMouseClickedCancelBtn" prefHeight="26.0" prefWidth="77.0" text="Abbrechen" />
   <Label layoutX="10.0" layoutY="27.0" prefHeight="27.0" prefWidth="342.0" text="Sie können das Systema nun verwenden" textAlignment="CENTER" textOverrun="CLIP">
     <font>
        <Font name="System Bold" size="18.0" />
     </font>
  </Label>
   </children>
  </AnchorPane>