java - 将值/字符串返回到 JTextField，IndexoutofboundsException

Question

根据另一个 Headfirst 练习，我在用车辆数据填充 GUI 时遇到了麻烦。我使用 Controller 类来管理我的车辆对象类。由于某种原因，我遇到了索引超出范围异常。

GUI类

public class ShowroomDriver{
    public static Showroom Cars = new Showroom("Cars");
    public static void main(String[] args) {           
        Showroom Cars = new Showroom("Cars");
        Vehicle vechicle1 = new Vehicle("Ford"); 

        Cars.addVehicle(vechicle1);
        GuiInterface gui = new GuiInterface("Car Showroom");
    }

    private static class GuiInterface extends JFrame {
        private JButton saleButton, previousButton, nextButton;
        private static JTextField textField1;
        private JLabel label1;
        private JPanel[] p = new JPanel[5];
        public GuiInterface(String sTitle) {
            super(sTitle);
            setLayout(new FlowLayout());
            previousButton = new JButton("Previous Car");
            nextButton = new JButton("Next Car");
            saleButton = new JButton("Sale");          

            for(int i = 0; i < 5; i++){
                p[i] = new JPanel();
            }

            Container contentPane = getContentPane();
            contentPane.setLayout(new BorderLayout());
            JPanel formPanel = new JPanel(new GridLayout(1, 2));


            textField1 = new JTextField(10);            
            label1 = new JLabel("Manufacture");

            p[0].add(label1);
            p[1].add(textField1);


            for(int i = 0; i < 2; i++){
                formPanel.add(p[i]);
            }

            contentPane.add(formPanel, BorderLayout.CENTER);

            this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            this.setSize(300,300);
            this.setResizable(false);
            this.setLocationRelativeTo(null);
            getField();

            this.setVisible(true);
        }

        private void getField(){
            textField1.setText(Cars.currentVehicle().getManufacutre());
        }
    }
}

Controller 类

public class Showroom{
    private ArrayList<Vehicle> vehiclesSold = new ArrayList();
    private ArrayList<Vehicle> theVehicles;
    private String vechicleType;
    private int arrayPosition = 0;

    public Showroom(String type){
        vechicleType = type;
        theVehicles = new ArrayList<Vehicle>();
    }

    public boolean addVehicle(Vehicle newVehicle){
        theVehicles.add(newVehicle);
        return true;
    }

    public Vehicle currentVehicle(){
        return theVehicles.get(arrayPosition);
    }

    public void getVehicles(){
        System.out.println("---Vehicle Type: " + vechicleType +"---");
        for(Vehicle nextVehicle : theVehicles){
            System.out.println(nextVehicle.toString());
        }
    }
}

车辆类别

public class Vehicle{
    private String Manufacture
    Vehicle(String Manufacture){ //There are more
        this.Manufacture = Manufacture;
        }
    }

    @Override
    public String toString(){
        String s = "Maufacture: " + getManufacutre()
                "\n";
        return s;
    }

    public String getManufacutre() { return this.Manufacture; }
}

Answer 1

如果没有更多代码，就无法判断错误来自何处。但从这段代码来看，唯一可能出现 IndexOutOfBoundsException 的地方是

return theVehicles.get(arrayPosition);

你的问题是，arrayPosition是错误的。
尝试调试您的代码以找出到底出了什么问题，或发布更多代码

编辑:您似乎对 static 关键字的作用有误解。
静态对象或方法是只在运行时实例化一次的东西。
例如，您在 class ShowhroomDriver 中声明 Cars 属性意味着该类 ShowroomDriver 有一个single 类属性名为Cars(顺便说一句 - 不要让属性以大写字符开头。这非常令人困惑)。

您想要的是将 ShowRoom 实例(您的 Cars 属性)传递给您的类 GuiInterface (同时删除 >static 关键字)通过其构造函数，如下所示:

// ...
private Showroom cars;
public GuiInterface(String sTitle, Showroom cars) {
    // ...
    this.cars = cars;
    // ...
}

然后，而不是

private void getField(){
    textField1.setText(Cars.currentVehicle().getManufacutre());
}

你写

private void getField(){
    textField1.setText(this.cars.currentVehicle().getManufacutre());
}

同时删除除 main 方法中的关键字之外的所有 static 关键字。