Niezrozumiały dla mnie log kompilacji

Question

Zaczynam programować w JavaFX i natknąłem się na problem, którego nie mogę naprawić. Otóż taki log kompilacji: 

Exception in Application start method
Exception in thread "main" 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$launchApplication$155(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: 
/C:/Users/Jonatan/IdeaProjects/Social%20Network/target/classes/FXML_LoginRegisterPanel/Main.fxml
 
    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2571)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
    at LoginRegisterPanel.Main.start(Main.java:22)
    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)
    ... 1 more
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.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.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2566)
    ... 12 more
Caused by: java.lang.NullPointerException: Children: child node is null: parent = StackPane[id=mainStackPane]
    at javafx.scene.Parent$2.onProposedChange(Parent.java:435)
    at com.sun.javafx.collections.VetoableListDecorator.add(VetoableListDecorator.java:206)
    at LoginRegisterPanelController.MainController.setScreen(MainController.java:43)
    at LoginRegisterPanelController.MainController.loadLoginPanel(MainController.java:38)
    at LoginRegisterPanelController.MainController.initialize(MainController.java:21)
    ... 23 more 

prawdopodobnie podczas

public void setScreen(Pane pane) {
        mainStackPane.getChildren().clear();
        mainStackPane.getChildren().add(pane);
    }

Answer 1

Ciężko z samych logów coś wymyślić no ale jak dla mnie to debugger w dłoń i sprawdzić czemu mainStackPane ma child nulla...

Comments

package LoginRegisterPanel;

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

/**
 * Created by Jonatan on 2016-12-06.
 */
public class Main extends Application {

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

    @Override
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader loader = new FXMLLoader(this.getClass().getResource("/FXML_LoginRegisterPanel/Main.fxml"));

        StackPane stackPane = loader.load();

        Scene scene = new Scene(stackPane, 330, 250);

        primaryStage.setScene(scene);

        primaryStage.show();
    }
}

import java.io.IOException;

/**
 * Created by Jonatan on 2016-12-06.
 */
public class MainController {

    @FXML
    StackPane mainStackPane;

    @FXML
    public void initialize() {
        loadLoginPanel();
    }

    public void loadLoginPanel() {
        FXMLLoader loader = new FXMLLoader(this.getClass().getResource("/FXML_LoginRegisterPanel/Login.fxml"));

        Pane pane = null;

        try {
            pane = loader.load();
        } catch(IOException e) {

        }

        LoginController loginController = loader.getController();
        loginController.setMainController(this);

        setScreen(pane);
    }

    public void setScreen(Pane pane) {
        mainStackPane.getChildren().clear();
        mainStackPane.getChildren().add(pane);
    }

    public void setScreen(GridPane gridPane) {
        mainStackPane.getChildren().clear();
        mainStackPane.getChildren().add(gridPane);
    }
}

Wywala błąd przy 

mainStackPane.getChildren().add(pane);

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Dodaj do bloku catch obsługe wyjątków i sprawdź czy load prawidłowo pobiera pane. Bo w twoim logu masz null pointer exeption tak jakby pane nadal było nulem

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Po ponad 4 godzinach znalazłem błąd. W jednym miejscu w kontrolerze dla zmiennej dałem typ Label zamiast CheckBox. Dzięki za pomocne sugestie.