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java - 无法使用包中的方法将对象存储在 List 中？
转载 作者：太空宇宙 更新时间：2023-11-04 13:20:01 25 4
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所以有人请让我知道我在这里做错了什么。我的目标是将摩托车添加到 mInventory(我已创建并从单独的包导入)。但是，我的代码中仍然出现错误。我参加了 Treehouse 的 Java 类(class)，现在我正尝试使用 IntelliJ，但我不禁觉得他们真的只是把我们扔到那里，而没有真正解释 IntelliJ 的工作原理。有人给我一些建议吗？？？

这是 Main.java:

package sample;

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

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("/fxml/sample.fxml"));

        primaryStage.setTitle("Store Motorcycle");
        primaryStage.setScene(new Scene(root, 500, 400));
        primaryStage.show();
    }


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

这是我的 Controller 类:

package sample;

import javafx.event.ActionEvent;
import sample.com.gardnerwebideas.Inventory;
import sample.com.gardnerwebideas.Motorcycle;

import javafx.fxml.FXML;
import javafx.scene.control.TextField;

import java.util.ArrayList;

public class Controller {

    @FXML private TextField bikeYear;
    @FXML private TextField bikeMake;
    @FXML private TextField bikeModel;
    @FXML private TextField bikeColor;
    @FXML private TextField bikePrice;

    private Inventory mInventory = new Inventory();

    public void userCreateBike(ActionEvent actionEvent) {
        Motorcycle motorcycle = newMotorcycle();
        System.out.printf("Adding: %s", motorcycle);
        mInventory.addMotorcycle(motorcycle);
    }

    public Motorcycle newMotorcycle() {
        String year = bikeYear.getText();
        String make = bikeMake.getText();
        String model = bikeModel.getText();
        String color = bikeColor.getText();
        String price = bikePrice.getText();
        return new Motorcycle(year, make, model, color, price);
    }

}

这是我的库存类:

package sample.com.gardnerwebideas;

import java.util.ArrayList;
import java.util.List;

public class Inventory {

    private List<Motorcycle> mInventory;

    public Inventory() {
        mInventory = new ArrayList<>();
    }

    public void addMotorcycle(Motorcycle motorcycle) {
        mInventory.add(motorcycle);
    }

    public int getInventoryCount() {
        return mInventory.size();
    }

    @Override
    public String toString() {
        return "Inventory{" +
                "mInventory=" + mInventory +
                '}';
    }
}

最后是摩托车类:

package sample.com.gardnerwebideas;

public class Motorcycle {

    private String mYear;
    private String mMake;
    private String mModel;
    private String mColor;
    private String mPrice;

    public Motorcycle(String year, String make, String model, String color, String price) {
        mYear = year;
        mMake = make;
        mModel = model;
        mColor = color;
        mPrice = price;
    }

    public String getYear() {
        return mYear;
    }

    public String getMake() {
        return mMake;
    }

    public String getModel() {
        return mModel;
    }

    public String getColor() {
        return mColor;
    }

    public String getPrice() {
        return mPrice;
    }

    @Override
    public String toString() {
        return "Motorcycle:" +
                "Year: " + mYear + "\n" +
                "Make: " + mMake + "\n" +
                "Model: " + mModel + "\n" +
                "Color: " + mColor + "\n" +
                "Price: " + mPrice + "\n";
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Motorcycle that = (Motorcycle) o;

        if (mYear != null ? !mYear.equals(that.mYear) : that.mYear != null) return false;
        if (mMake != null ? !mMake.equals(that.mMake) : that.mMake != null) return false;
        if (mModel != null ? !mModel.equals(that.mModel) : that.mModel != null) return false;
        if (mColor != null ? !mColor.equals(that.mColor) : that.mColor != null) return false;
        return !(mPrice != null ? !mPrice.equals(that.mPrice) : that.mPrice != null);

    }

    @Override
    public int hashCode() {
        int result = mYear != null ? mYear.hashCode() : 0;
        result = 31 * result + (mMake != null ? mMake.hashCode() : 0);
        result = 31 * result + (mModel != null ? mModel.hashCode() : 0);
        result = 31 * result + (mColor != null ? mColor.hashCode() : 0);
        result = 31 * result + (mPrice != null ? mPrice.hashCode() : 0);
        return result;
    }
}

FXML:

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

<?import java.lang.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.text.*?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.text.Text?>
<?import javafx.scene.control.TextField?>

<GridPane alignment="CENTER"
          stylesheets="/css/style.css"
          xmlns="http://javafx.com/javafx/8"
          xmlns:fx="http://javafx.com/fxml/1"
          fx:controller="sample.Controller">

   <children>

       <Text styleClass="title"
             text="Add a motorcycle:"
             GridPane.columnSpan="2"
             GridPane.halignment="CENTER"
             GridPane.rowIndex="0" />

       <Text styleClass="textTitle"
             text="Year:"
             GridPane.columnIndex="0"
             GridPane.rowIndex="1" />

       <TextField fx:id="bikeYear"
                  GridPane.columnIndex="1"
                  GridPane.rowIndex="1" />

       <Text styleClass="textTitle"
             text="Make:"
             GridPane.columnIndex="0"
             GridPane.rowIndex="2" />

       <TextField fx:id="bikeMake"
                  alignment="TOP_LEFT"
                  GridPane.columnIndex="1"
                  GridPane.rowIndex="2" />

       <Text styleClass="textTitle"
             text="Model:"
             GridPane.columnIndex="0"
             GridPane.rowIndex="3" />

       <TextField fx:id="bikeModel"
                  GridPane.columnIndex="1"
                  GridPane.rowIndex="3" />

       <Text styleClass="textTitle"
             text="Color:"
             GridPane.columnIndex="0"
             GridPane.rowIndex="4" />

       <TextField fx:id="bikeColor"
                  GridPane.columnIndex="1"
                  GridPane.rowIndex="4" />

       <Text styleClass="textTitle"
             text="Price:"
             GridPane.columnIndex="0"
             GridPane.rowIndex="5" />

       <TextField fx:id="bikePrice"
                  GridPane.columnIndex="1"
                  GridPane.rowIndex="5" />

       <Button onAction="#userCreateBike"
               styleClass="button"
               text="Submit"
               GridPane.columnSpan="2"
               GridPane.halignment="CENTER"
               GridPane.rowIndex="6" />

   </children>

</GridPane>

如果有任何不清楚的地方，让我重复一遍...导致我出现问题的是以下行:mInventory.addMotorcycle(摩托车);除此之外，我的代码可以工作。它从我的 TextFields 获取信息，甚至将其打印到控制台......但它不会将新的摩托车添加到 mInventory。

哦...这是我收到的错误消息...

java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
    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:8411)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$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$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:352)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:275)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$355(GlassViewEventHandler.java:388)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:387)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
    ... 45 more
Caused by: java.lang.NullPointerException
    at sample.Controller.userCreateBike(Controller.java:26)
    ... 55 more

最佳答案

您的 Controller 没有构造函数，也没有 initialize() 方法。

首先在现在所在的位置定义成员private Inventory mInventory;，然后在构造函数或initialize()方法中创建新对象(mInventory = new Inventory();)。

关于java - 无法使用包中的方法将对象存储在 List<Object> 中？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33159848/

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