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i want to create a little quiz app with javafx, scenebuilder and sqlite. right now i struggle to give the created questions i wrote in sqlite over to my controller. i want to call the setQuestions method every time i start the quiz, so i made "ControllerQuiz controllerQuiz = fxmlLoader.getController();"

Here is my Category menu where i want to give the questions from SQLite over:

    @FXML
    private Button Computer;

    @FXML
    private Button Science;

    @FXML
    private Button Java;

    @FXML
    private Button Animal;

    @FXML
    private Button City;

    @FXML
    private Button Country;

    @FXML
    private Label Lable;

    @FXML
    private HBox statusHBox;

    @FXML
    private Circle dbstatuslight;

    @FXML
    private Button OK;

    @FXML
    private Button abort;

    // --------- Arraylist --------
    List<String> categoryList = new ArrayList<String>();

    List<Question> quizQuestionList = new ArrayList<>();

    Database database = new Database();
    QuestionBank questionBank = new QuestionBank();

    @FXML
    void ComputerButton(ActionEvent event) {
            Button button = (Button) event.getSource();
            getCategory(button.getText(),button);
    }

    @FXML
    void ScienceButton(ActionEvent event) {
            Button button = (Button) event.getSource();
            getCategory(button.getText(),button);
    }

    @FXML
    void JavaButton(ActionEvent event) {
            Button button = (Button) event.getSource();
            getCategory(button.getText(),button);
    }

    @FXML
    void AnimalButton(ActionEvent event) {
            Button button = (Button) event.getSource();
            getCategory(button.getText(),button);
    }

    @FXML
    void CityButton(ActionEvent event) {
            Button button = (Button) event.getSource();
            getCategory(button.getText(), button);
    }

    @FXML
    void CountryButton(ActionEvent event) {
            Button button = (Button) event.getSource();
            getCategory(button.getText(), button);
    }

    //------- HBox --------

    @FXML
    void OKButton(ActionEvent event) {

            for (String category: categoryList) {
                    questionBank.loadCategoryQuestions(database.getStatement(), category);
            }

            quizQuestionList = questionBank.getQuestionList();

            for (Question question: quizQuestionList) {
                    System.out.println("ID: " + question.getQuestion_id());
            }

            Button okButton = (Button) event.getSource();
            Stage stage = (Stage) okButton.getScene().getWindow();
            stage.close();

            try {
                    startQuiz();
            } catch (IOException e) {
                    e.printStackTrace();
            }
    }

    @FXML
    void abortButton(ActionEvent event) {
            Computer.setDisable(false);
            Java.setDisable(false);
            Science.setDisable(false);
            City.setDisable(false);
            Country.setDisable(false);
            Animal.setDisable(false);
            statusHBox.setDisable(true);
            Lable.setText(" ");
    }

    @Override
    public void initialize(URL location, ResourceBundle resources) {
            statusHBox.setDisable(true);

            //Database connection
            boolean dbConnection = database.open();

            if(dbConnection) {
                    dbstatuslight.setFill(Color.GREEN);
            } else {
                    dbstatuslight.setFill(Color.RED);
            }
    }

    //---------- methods ----------
    private void getCategory(String category, Button button) {
            categoryList.add(category);
            Lable.setText(Lable.getText() + " " + category);

            button.setDisable(true);
            statusHBox.setDisable(false);
    }

    private void startQuiz() throws IOException {
            Stage stage3 = new Stage();
            stage3.setTitle("Quiz");

            FXMLLoader fxmlLoader = new FXMLLoader();

            AnchorPane root = (AnchorPane) fxmlLoader.load(new File("src/main/java/org/example/quizapp/controller/quiz.fxml").toURI().toURL());
            //AnchorPane root = (AnchorPane)  fxmlLoader.load(getClass().getClassLoader().getResource("/main/java/org/example/quizapp/controller/quiz.fxml").openStream());

            ControllerQuiz controllerQuiz = fxmlLoader.getController();
            controllerQuiz.setQuestions((ArrayList<Question>) quizQuestionList);


            Scene scene3 = new Scene(root);

            stage3.setScene(scene3);
            stage3.setResizable(false);
            stage3.show();

    }

}

my Controller for that category menu:

@FXML
private Label Question;

@FXML
private Button YES;

@FXML
private Button NO;

@FXML
private Label questionCounter;

@FXML
private Label score;

@FXML
private Label Highscore;

private ArrayList<Question> questionList = new ArrayList<>();

@FXML
void answerButton(ActionEvent event) {

}

//methods
public void setQuestions(ArrayList<org.example.quizapp.menu.questions.Question> qList) {
    questionList = qList;

    for (Question question: questionList) {
        System.out.println(question.getQuestion_id());
    }
}

}

the question bank:

private List<Question> questionList = new ArrayList<>();

public void loadCategoryQuestions (Statement statement, String categoryTable) {
    String QUERY_DATA_FROM_TABLE = "SELECT * FROM " + categoryTable;
    ResultSet resultSet = null;

    try {
        resultSet = statement.executeQuery(QUERY_DATA_FROM_TABLE);

        while (resultSet.next()) {
            int question_id = resultSet.getInt(1);
            String question_text = resultSet.getString(2);
            boolean question_answer;
            if (resultSet.getInt(3) == 1) {
                question_answer = true;
            } else {
                question_answer = false;
            }
            String question_complement = resultSet.getString(4);

            Question question = new Question(question_id, question_text, question_answer, question_complement);

            questionList.add(question);

        }
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

public List<Question> getQuestionList() {
    return questionList;
}

public void setQuestionList(List<Question> questionList) {
    this.questionList = questionList;
}

}

the error log i get when i try to compile:

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1787)
at javafx.fxml/javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1670)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Node.fireEvent(Node.java:8885)
at javafx.controls/javafx.scene.control.Button.fire(Button.java:203)
at javafx.controls/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:206)
at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3890)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1885)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2618)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:409)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:299)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:447)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:412)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:446)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
at javafx.graphics/com.sun.glass.ui.mac.MacView.notifyMouse(MacView.java:127)

Caused by: java.lang.reflect.InvocationTargetException at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:564) at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:76) at jdk.internal.reflect.GeneratedMethodAccessor2.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:564) at javafx.base/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:273) at javafx.fxml/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:83) at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1782) ... 44 more Caused by: java.lang.NullPointerException at quizapp/org.example.quizapp.menu.category.CategoryMenu.startQuiz(CategoryMenu.java:178) at quizapp/org.example.quizapp.menu.category.CategoryMenu.OKButton(CategoryMenu.java:127) ... 55 more

Caused by: java.lang.reflect.InvocationTargetException at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:564) at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:76) at jdk.internal.reflect.GeneratedMethodAccessor2.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:564) at javafx.base/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:273) at javafx.fxml/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:83) at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1782) ... 44 more Caused by: java.lang.NullPointerException at quizapp/org.example.quizapp.menu.category.CategoryMenu.startQuiz(CategoryMenu.java:178) at quizapp/org.example.quizapp.menu.category.CategoryMenu.OKButton(CategoryMenu.java:127)
ポリゴンD
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    It will be helpful if you can also show stacktrace. – Ankit Beniwal Jun 02 '20 at 17:49
  • 2
    1. You're calling the `static` `FXMLLoader.load(URL)` method to load the FXML. Because this method is `static`, it doesn't affect the `FXMLLoader` instance, and `loader.getController()` will return null. Instead, set the location on the `FXMLLoader` instance and call the *instance* method `loader.load()` with no parameters. 2. Your FXML path is almost certainly wrong. Why are you trying to reference the source directory at runtime? See https://stackoverflow.com/questions/61531317. 3. Please post the complete stack trace in the question. It would also help if you created a minimal example. – James_D Jun 02 '20 at 17:50
  • i added the stack trace, thanks for the comments – ポリゴンD Jun 02 '20 at 18:32

0 Answers0