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I am trying to call the showRecords method in MainApp.java from LoginController.java, but I am facing some difficulties while trying to accomplish this. When I use the constructor so that I can use showRecords, a InvocationTargetException was thrown and I have no idea how to fix. I have tried to follow the answers in other similar questions, but I could not manage to fix the code myself.

How can I call showRecords and methods in other classes in the future?

MainApp.java

package com.fivefourdee.aglaea;

import java.io.IOException;

import com.fivefourdee.aglaea.record.model.Person;

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class MainApp extends Application{
    static final String title = "title";
    private Stage primaryStage;
    private BorderPane rootLayout;
    private ObservableList<Person> personData = FXCollections.observableArrayList();
    @Override
    public void start(Stage primaryStage){
        this.primaryStage = primaryStage;
        this.primaryStage.setTitle(getAppTitle());
        initRootLayout();
        showLogin();
    }
    public MainApp(){
    }
    public void initRootLayout(){
        try{
            FXMLLoader loader = new FXMLLoader();
            loader.setLocation(MainApp.class.getResource("record/view/RootLayout.fxml"));
            rootLayout = (BorderPane)loader.load();
            Scene scene = new Scene(rootLayout);
            primaryStage.setScene(scene);
            primaryStage.show();
        }catch(IOException e){
            e.printStackTrace();
        }
    }
    public void showLogin(){
        try{
            FXMLLoader loader = new FXMLLoader();
            loader.setLocation(MainApp.class.getResource("login/view/LoginPanel.fxml"));
            BorderPane records = (BorderPane)loader.load();
            rootLayout.setCenter(records);
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    public void showRecords(){
        try{
            FXMLLoader loader = new FXMLLoader();
            loader.setLocation(MainApp.class.getResource("record/view/RecordViewer.fxml"));
            AnchorPane records = (AnchorPane)loader.load();
            rootLayout.setCenter(records);
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    public static void main(String[] args){
        launch(args);
    }
    public static String getAppTitle(){
        return title;
    }
    public ObservableList<Person> getPersonData(){
        return personData;
    }
    public Stage getPrimaryStage(){
        return primaryStage;
    }
}

LoginController.java:

package com.fivefourdee.aglaea;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.paint.Color;

public class LoginController{
    int trials=5;
    @FXML
    private TextField userfield;
    @FXML
    private PasswordField passwordfield;
    @FXML
    private void onLogin(ActionEvent event){
        if(userfield.getText().equals("admin")&&passwordfield.getText().equals("admin")){
            /* do other things */
            MainApp mainapp = new MainApp();
            mainapp.showRecords();
        }
        else{
            /* do other things */
        }
    }
}

Exception:

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1770)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1653)
    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:8390)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.skin.ButtonSkin.lambda$new$279(ButtonSkin.java:102)
    at com.sun.javafx.scene.control.skin.ButtonSkin$$Lambda$154/400371281.run(Unknown Source)
    at com.sun.javafx.scene.KeyboardShortcutsHandler.processAccelerators(KeyboardShortcutsHandler.java:347)
    at com.sun.javafx.scene.KeyboardShortcutsHandler.dispatchBubblingEvent(KeyboardShortcutsHandler.java:163)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8390)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.forwardToParent(TextInputControlBehavior.java:432)
    at com.sun.javafx.scene.control.behavior.TextFieldBehavior.fire(TextFieldBehavior.java:183)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callAction(TextInputControlBehavior.java:178)
    at com.sun.javafx.scene.control.behavior.BehaviorBase.callActionForEvent(BehaviorBase.java:218)
    at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callActionForEvent(TextInputControlBehavior.java:127)
    at com.sun.javafx.scene.control.behavior.BehaviorBase.lambda$new$75(BehaviorBase.java:135)
    at com.sun.javafx.scene.control.behavior.BehaviorBase$$Lambda$88/263344979.handle(Unknown Source)
    at com.sun.javafx.event.CompositeEventHandler$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$KeyHandler.process(Scene.java:3965)
    at javafx.scene.Scene$KeyHandler.access$1800(Scene.java:3911)
    at javafx.scene.Scene.impl_processKeyEvent(Scene.java:2040)
    at javafx.scene.Scene$ScenePeerListener.keyEvent(Scene.java:2502)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:197)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$KeyEventNotification.run(GlassViewEventHandler.java:147)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleKeyEvent$349(GlassViewEventHandler.java:228)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$$Lambda$179/475935975.get(Unknown Source)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:404)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:227)
    at com.sun.glass.ui.View.handleKeyEvent(View.java:546)
    at com.sun.glass.ui.View.notifyKey(View.java:956)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
    at com.sun.glass.ui.win.WinApplication$$Lambda$36/2117255219.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1765)
    ... 67 more
Caused by: java.lang.NullPointerException
    at com.fivefourdee.aglaea.MainApp.showRecords(MainApp.java:59)
    at com.fivefourdee.aglaea.LoginController.onLogin(LoginController.java:24)
    ... 77 more
54D
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  • The `MainApp` instance you create is different from the one you launch and call `initRootLayout` for, therefore yielding a NPE on `rootLayout.setCenter(records);`. You can make this work by passing the launched `MainApp` instance as described in the first dupe... – fabian Oct 06 '17 at 17:10
  • I see, then how do I get the launched `MainApp` instance for passing?? – 54D Oct 08 '17 at 05:59
  • It's available in the `start` method (or any instance methods of the same instance) via `this`. – fabian Oct 08 '17 at 08:44
  • Sorry, I don't seem to get it >_ – 54D Oct 08 '17 at 15:41

0 Answers0