我正在尝试扩展 Uni 提供给我们的 Java 程序，但我无法让该程序使用新 class 中的方法

Question

所以，首先我是一个非常业余的 Java 程序员，它只是一个模块，然后就结束了。

条件是覆盖我们的 TurtleGraphics 程序中预定义的 'about()' 命令。

如果我将覆盖放在 GUI class 和其他所有内容中，我可以让它工作，但是当我尝试创建一个 'ExtendedTurtleGraphics' class 并尝试调用它时，它什么都不做，不抛出错误，什么也不做。

这是扩展的Class和内容

public class ExtendedTurtleGraphics extends TurtleGraphics {
TurtleGraphics TG = new TurtleGraphics();
theTurtle turtle = new theTurtle();
String Command;
@Override
public void about() {
    super.about();
    System.out.print("Testing..."); //Working!
    Command = "backward 100";
    turtle.getCommand(Command, this);
    Command = "penDown";
    turtle.getCommand(Command, this);
    Command = "forward 200";
    turtle.getCommand(Command, this);
    Command = "turnright 120";
    turtle.getCommand(Command, this);
    Command = "forward 50";
    turtle.getCommand(Command, this);
}

/*@Override
public void circle(int radius) {
    super.circle(radius);

    }*/
}

这是整个 GUI class，关于部分在后面

public class myGUI extends JPanel{

    static JTextField commandbox;
    boolean isSaved = false;
    TurtleGraphics TG = new TurtleGraphics();
    theTurtle turtle = new theTurtle();
    TurtleGraphics ETG = new ExtendedTurtleGraphics();
    public myGUI()
    {
        JFrame MFrame = new JFrame();
        setLayout(new BorderLayout());
        setBackground(Color.white);
        commandbox = new JTextField(5);
        MenuBr mb = new MenuBr();
        MFrame.setJMenuBar(mb);
        MFrame.add(commandbox, BorderLayout.SOUTH);
        commandbox.addActionListener(new MyActionListener());
        MFrame.add(TG);
        MFrame.setSize(640, 480);
        MFrame.setVisible(true);
        MFrame.validate();
        MFrame.repaint();
        ExtendedTurtleGraphics ETG;

    }
    public static void infoBox(String infoMessage, String titleBar)
    {
        JOptionPane.showMessageDialog(null, infoMessage, titleBar, JOptionPane.INFORMATION_MESSAGE);
    }
    class MenuBr extends JMenuBar implements ActionListener {
        JMenu fileMnu = new JMenu("File");
        JMenuItem newMnuI = new JMenuItem("New");
        JMenuItem openMnuI = new JMenuItem("Load");
        JMenuItem saveMnuI = new JMenuItem("Save");
        JMenuItem closeMnuI = new JMenuItem("Exit");
        JMenu helpMnu = new JMenu("Help");
        JMenuItem aboutMnuI = new JMenuItem("About");


        MenuBr() {
            add(fileMnu);
            fileMnu.add(newMnuI);
            fileMnu.add(openMnuI);
            fileMnu.add(saveMnuI);
            fileMnu.add(closeMnuI);
            newMnuI.addActionListener(this);
            openMnuI.addActionListener(this);
            saveMnuI.addActionListener(this);
            closeMnuI.addActionListener(this);
            add(helpMnu);
            helpMnu.add(aboutMnuI);
            aboutMnuI.addActionListener(this);
        }

        public void actionPerformed(ActionEvent e) {
            if (e.getSource() == newMnuI) {
                TG.reset();
                TG.turnLeft(90);
                TG.clear();
                TG.penDown();
            }
            if (e.getSource() == openMnuI) {
                if (isSaved == true) {
                    String loadName = JOptionPane.showInputDialog("Enter Load File Path (Excluding .png) :");
                    loadName = loadName + ".png";
                    try {
                        BufferedImage loadedImage = ImageIO.read(new File(loadName));
                        TG.setBufferedImage(loadedImage);
                    } catch (IOException exception) {
                        System.out.println(exception.getMessage());
                    }
                } else if (isSaved == false) {
                    int n = JOptionPane.showConfirmDialog(null, "Save before loading?", "Are you sure?", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
                    System.out.println(n);
                    if (n == 0) {
                        Graphics g = TG.getGraphicsConext();
                        BufferedImage i = TG.getBufferedImage();
                        String fileName = JOptionPane.showInputDialog("Enter Save File Path (Excluding .png): ");
                        fileName = fileName + ".png";
                        File file = new File(fileName);
                        try {
                            ImageIO.write(i, "png", file);
                        } catch (IOException el) {
                            el.printStackTrace();
                        }
                        String loadName = JOptionPane.showInputDialog("Enter Load File Path (Excluding .png) :");
                        loadName = loadName + ".png";
                        try {
                            BufferedImage loadedImage = ImageIO.read(new File(loadName));
                            TG.setBufferedImage(loadedImage);
                        } catch (IOException exception) {
                            System.out.println(exception.getMessage());
                        }
                    } else if (n == 1) {
                        String loadName = JOptionPane.showInputDialog("Enter Load File Path (Excluding .png) :");
                        loadName = loadName + ".png";
                        try {
                            BufferedImage loadedImage = ImageIO.read(new File(loadName));
                            TG.setBufferedImage(loadedImage);
                        } catch (IOException exception) {
                            System.out.println(exception.getMessage());
                        }
                    }
                }
            }
            if (e.getSource() == saveMnuI) {
                isSaved = true;
                Graphics g = TG.getGraphicsConext();
                BufferedImage i = TG.getBufferedImage();
                String fileName = JOptionPane.showInputDialog("Enter File Path (Excluding .png): ");
                fileName = fileName + ".png";
                File file = new File (fileName);
                try{
                    ImageIO.write(i, "png", file);
                } catch (IOException el) {
                    el.printStackTrace();
                }
            }
            if (e.getSource() == closeMnuI) {
                if (isSaved == true)
                {
                    System.exit(0);
                }
                else
                {
                    int n = JOptionPane.showConfirmDialog(null, "Save before quitting?", "Are you sure?", JOptionPane.YES_NO_OPTION, JOptionPane.QUESTION_MESSAGE);
                    System.out.println(n);
                    if (n == 0)
                    {
                        Graphics g = TG.getGraphicsConext();
                        BufferedImage i = TG.getBufferedImage();
                        String fileName = JOptionPane.showInputDialog("Enter File Path (Excluding .png): ");
                        fileName = fileName + ".png";
                        File file = new File (fileName);
                        try{
                            ImageIO.write(i, "png", file);
                        } catch (IOException el) {
                            el.printStackTrace();
                        }
                        System.exit(0);
                    }
                    else if (n == 1)
                    {
                        System.exit(0);
                    }
                }
            }

这是关于部分

        if (e.getSource() == aboutMnuI) {
            ETG.clear();
            ETG.about();
            ImageIcon icon = new ImageIcon("FilePath");
            JOptionPane.showMessageDialog(null, "Turtle Graphics\nJoe Bloggs\n4FS1\nOOP Assessment 2020", "About", JOptionPane.INFORMATION_MESSAGE, icon);
            }
        }
    }
    class MyActionListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {

            if (e.getSource() == commandbox) {

                String command = commandbox.getText();
                isSaved = false;
                turtle.getCommand(command, TG);
                commandbox.setText("");

            }
        }
    }

}

theTurtle Java Class.

public class theTurtle {
    //ArrayList<String> oldCommands = new ArrayList<>();

    public void getCommand(String command, TurtleGraphics TG)
    {
        String[]entries = command.split(" ");
        int var = -1;
        String norm = entries[0];
        if (entries.length == 2)
        {
            var = Integer.parseInt(entries[1]);
        }
        getMethod(norm, var, TG);
    }
    private void getMethod(String command, int var, TurtleGraphics TG)
    {
        if (command.toLowerCase().equals("penup"))
        {
            TG.penUp();
        }
        else if (command.toLowerCase().equals("pendown"))
        {
            TG.penDown();
        }
        else if (command.toLowerCase().equals("turnleft"))
        {
            if (var==-1)
            {
                TG.turnLeft();
            }
            else{
                TG.turnLeft(var);
            }
        }
        else if (command.toLowerCase().equals("turnright"))
        {
            if (var==-1)
            {
                TG.turnRight();
            }
            else{
                TG.turnRight(var);
            }
        }
        else if (command.toLowerCase().equals("forward"))
        {
            if (var == -1 || var <= 0)
            {
                errorEcho(1);
            }
            else{
                TG.forward(var);
            }
        }
        else if (command.toLowerCase().equals("backward"))
        {
            if (var == -1 || var <= 0)
            {
                errorEcho(1);
            }
            else{
                TG.turnRight(180);
                TG.forward(var);
                TG.turnRight(180);
            }
        }
        else if (command.toLowerCase().equals("black"))
        {
            TG.setPenColour(Color.black);
        }
        else if (command.toLowerCase().equals("red"))
        {
            TG.setPenColour(Color.red);
        }
        else if (command.toLowerCase().equals("green"))
        {
            TG.setPenColour(Color.green);
        }
        else if (command.toLowerCase().equals("reset"))
        {
            TG.reset();
            TG.turnLeft(90);
            TG.clear();
            TG.penDown();
        }
        else if (command.toLowerCase().equals("circle"))
        {
            if (var == -1 || var <= 0)
            {
                errorEcho(1);
            }
            else{
                TG.circle(var);
            }
        }
        else{
           myGUI.infoBox("Invalid Command", "ERROR!");
        }

    }
    private void errorEcho(int errorCode)
    {

        myGUI.infoBox("Missing Parameters", "ERROR!");
    }

}

The variables that are show stepping through about

Answer 1

删除TurtleGraphics TG = new TurtleGraphics();
将TG替换为this

这应该会让您朝着正确的方向前进。

@编辑

好吧，我们没有 TurtleGraphics 的代码，所以我们不能 100% 判断但是：

首先：在你的 gui 类中定义

TurtleGraphics TG = new TurtleGraphics();
theTurtle turtle = new theTurtle();
TurtleGraphics ETG = new ExtendedTurtleGraphics();

所以你在这里创建的结构是这样的

TurtleGraphics TG
theTurtle turtle
ExtendedTurtleGraphics ETG {
    TurtleGraphics TG      // You define a new instanct of TurtleGraphics called TG in the ETG object
    theTurle turtle  // You defined a new instance of theTurtle called turtle in the ETG object
}

请注意，您现在有两个 turtle 对象和两个 TurtleGraphicsObject（或者实际上是三个，因为 ETG 在扩展 TurtleGraphics 后也是一个 TurtleGraphics）

好吧，那么在 ExtendedTurtleGraphics 的 "about" 函数中，您运行对 "turtle" 命令，但请注意，这些命令是在以下海龟上执行的：

TurtleGraphics TG
theTurtle turtle
ExtendedTurtleGraphics ETG {
    TurtleGraphics TG    
    theTurle turtle     //  <- this one 
}

所以基本上，当您在 ETG 上运行 "about" 方法时，您在 "myGUI" class 中定义的 "turtle" 不会改变。这解释了为什么控制台输出在 about 方法中工作，但您看不到任何事情发生。

解决方法是删除 MyGui 初始化时的两行：

TurtleGraphics TG = new TurtleGraphics(); // remove this one
theTurtle turtle = new theTurtle();  // remove this one
TurtleGraphics ETG = new ExtendedTurtleGraphics();

然后从 ExtendedTurtleGraphics 中删除这一行：

TurtleGraphics TG = new TurtleGraphics(); // Remove this one

在 ExtendedTurtleGraphics 中创建 Turtle public。在这之后你的结构现在看起来像这样：

我的图形用户界面： ExtendedTurtleGraphic ETG { // ExtendedTurtleGraphics 对象是一个 TurtleGraphic
乌龟 }

现在，在 myGui class 中，将所有出现的 "TG" 替换为 "ETG"，将所有出现的 "turtle" 替换为 "ETG.turtle"

这意味着每次您想对海龟进行某些操作时，您都可以从 ETG 访问海龟实例，然后在调用 ExtendedTurtleGraphics 中的 "about" 方法时修改同一个对象。

@二次编辑：

使用参数 ETG 向 MyActionListener 添加构造函数，如下所示：

class MyActionListener implements ActionListener {

    private ExtendedTurtleGraphics ETG;

    public MyActionListener(ExtendedTurtleGraphics ETG){
        this.ETG = ETG;
    }

    @Override
    public void actionPerformed(ActionEvent e) {

        if (e.getSource() == commandbox) {

            String command = commandbox.getText();
            isSaved = false;
            ETG.turtle.getCommand(command, ETG);
            commandbox.setText("");

        }
    }
}

在 MyGui 中更改 Action 侦听器注册，如下所示：

commandbox.addActionListener(new MyActionListener(ETG));

我正在尝试扩展 Uni 提供给我们的 Java 程序，但我无法让该程序使用新 class 中的方法

I'm trying to extend a Java program given to us at Uni, and I can't get the program to use the methods in the new class

java

turtle-graphics