如何在JavaFX控制器文件中创建brandnew对象？

Question

今天我想为我的按钮提供动作。所以，我想要对新对象（用户）进行内联，并在其上做一些事情。但是我遇到了一些错误。我不能单独处理它。

用户类

package HomePlanner;

import javafx.beans.property.DoubleProperty;
import javafx.beans.property.StringProperty;

import java.time.LocalDate;
import java.util.ArrayList;
import java.util.Date;

/**
 * Created by mscib on 11.08.2016.
 */
public class User {
    private ArrayList<Expenses> listOfExpenses = new ArrayList<>();
    private DoubleProperty cash;


    public double getCash() {
        return cash.get();
    }

    public DoubleProperty cashProperty() {
        return cash;
    }

    public void setCash(double cash) {
        this.cash.set(cash);
    }

    public void addExpense(String name, String category, LocalDate date, double cost){
        if(name != null && category != null && date != null && (cash.getValue()-cost)>0){
            Expenses exp = new Expenses(category,name,cost,date);
            listOfExpenses.add(exp);
        }
    }

    public User(double cash){
        setCash(cash);
    }


}

费用等级

package HomePlanner;

import javafx.beans.property.DoubleProperty;
import javafx.beans.property.StringProperty;

import java.time.LocalDate;
import java.util.Date;
import java.util.Set;
import java.util.TreeSet;

/**
 * Created by mscib on 11.08.2016.
 */
public class Expenses {
    private String category;

    public String getCategory() {
        return category;
    }
    LocalDate date;

    private String name;

    public String getName() {
        return name;
    }

    private DoubleProperty cost;

    public double getCost() {
        return cost.get();
    }

    public DoubleProperty costProperty() {
        return cost;
    }

    public void setCost(double cost) {
        this.cost.set(cost);
    }

    public Expenses(String cat, String name, double cost,LocalDate date){
        this.date= date;
        category = cat;
        this.name=name;
        setCost(cost);
    }
}

控制器类

package HomePlanner;

import com.sun.javafx.css.converters.StringConverter;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.DatePicker;
import javafx.scene.control.TextField;
import javafx.scene.text.Text;
import javafx.event.ActionEvent;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class Controller {

    @FXML
    TextField nameField;
    @FXML
    TextField costField;
    @FXML
    DatePicker datePicker;
    @FXML
    ComboBox<String> categoryCombo;

    @FXML
    Button addButton;
    @FXML
    Button deleteButton;
    @FXML
    Button editButton;



    @FXML
    public void initialize(){
        User newUser = new User(100.0);
        categoryCombo.getItems().clear();
        categoryCombo.getItems().addAll(
                "Dom","Jedzenie","Odzież","Rozrywka"
        );

        addButton.setOnAction(event -> System.out.println(newUser.getCash()));

    }

}

主类

package HomePlanner;

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

public class Main extends Application {
    Parent root;
    @Override
    public void start(Stage primaryStage) throws Exception{
        FXMLLoader loader = new FXMLLoader(getClass().getResource("ExpensesOverview.fxml"));
        Parent root = loader.load();

        Controller myController = loader.getController();

        myController.initialize();
        Scene scene = new Scene(root);
        primaryStage.setScene(scene);
        primaryStage.show();
        primaryStage.sizeToScene();
    }


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

错误列表：

Exception in Application start method
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 com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    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.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException: 
/C:/Users/mscib/IdeaProjects/HomePlanner3/out/production/HomePlanner3/HomePlanner/ExpensesOverview.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 HomePlanner.Main.start(Main.java:16)
    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.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.loadImpl(FXMLLoader.java:2566)
    ... 12 more
Caused by: java.lang.NullPointerException
    at HomePlanner.User.setCash(User.java:27)
    at HomePlanner.User.<init>(User.java:38)
    at HomePlanner.Controller.initialize(Controller.java:37)
    ... 22 more
Exception running application HomePlanner.Main

祝福， 米哈尔。