如何获得我的MenuItems来从单独的类中调用方法？

Question

I currently have a project with three different classes. I have a driver class (main), a GUI panel with all the button listeners and gui components in and then a third class with the methods the Graphics Panel abides to.

I'm wondering how I would go about getting my JMenuItem "new" to call upon the clear method from my GraphicsPanel class.

Main Method:

import java.awt.Dimension;

import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;

public class guiDriver {

    public static void main(String[] args) {


    JFrame frame = new JFrame("Pen Simulator");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        GUIPanel panel = new GUIPanel();
        frame.add(panel);
        // there is a method to set minimum size
        frame.setMinimumSize(new Dimension(600, 400));

        JMenuBar menuBar = new JMenuBar();

        // File Menu
        JMenu fileMenu = new JMenu("File");
        JMenu helpMenu = new JMenu("Help");
        menuBar.add(fileMenu);
        menuBar.add(helpMenu);

        JMenuItem item1 = new JMenuItem("New");

        JMenuItem item2 = new JMenuItem("Load");

        JMenuItem item3 = new JMenuItem("Save");

        JMenuItem item4 = new JMenuItem("Exit");

        fileMenu.add(item1);
        fileMenu.add(item2);
        fileMenu.add(item3);
        fileMenu.add(item4);

        // Help Menu

        JMenuItem about = new JMenuItem("About");
        helpMenu.add(about);

        frame.setJMenuBar(menuBar); // setting the Frames menubar as the newly
                                    // created menubar
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

    }

}

GUIPANEL:

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class GUIPanel extends JPanel {

    private JTextField userCommand;
    private JLabel instruction1;
    private JButton instruct, clear;
    private GraphicsPanel graphics;
    private int penX, penY, angle;
    private int currentDirection = 0;

    private boolean penIsUp = false;
    private Color penColour;

    public GUIPanel() {

        graphics = new GraphicsPanel();

        setLayout(new BorderLayout());

        // SOUTH PANEL CONSTRUCTOR
        JPanel command = new JPanel();
        command.setLayout(new BoxLayout(command, BoxLayout.LINE_AXIS));
        instruction1 = new JLabel("Enter Command:");

        // BUTTO
        instruct = new JButton("Execute");
        instruct.addActionListener(new ButtonListener());
        clear = new JButton("Clear Graphics");

        // TEXT FIELD
        userCommand = new JTextField(10);

        command.add(instruction1);
        command.add(Box.createRigidArea(new Dimension(4, 0)));
        command.add(userCommand);
        command.add(Box.createRigidArea(new Dimension(2, 0)));
        command.add(instruct);
        command.add(Box.createRigidArea(new Dimension(2, 0)));
        command.add(clear);

        add(command, BorderLayout.SOUTH);
        add(graphics, BorderLayout.CENTER);

        init();

    }

    public void init() {

        penX = graphics.getWidth() / 2;
        penY = graphics.getHeight() / 2;
    }

    public void moveForward() {

        String command = userCommand.getText().toLowerCase();
        int distance = Integer.parseInt(command.replace("forward ", ""));

        userCommand.setText("");

        if (penIsUp == false) {
            if (currentDirection == 0) {
                graphics.drawLine(penColour, penX, penY, penX, (penY - distance));
                penY = penY - distance;
            }
            if (currentDirection == 1) {
                graphics.drawLine(penColour, penX, penY, penX + distance, penY);
                penX = penX + distance;
            }
            if (currentDirection == 2) {
                graphics.drawLine(penColour, penX, penY, penX, (penY + distance));
                penY = penY + distance;
            }
            if (currentDirection == 3) {
                graphics.drawLine(penColour, penX, penY, penX - distance, penY);
                penX = penX - distance;
            }
            graphics.repaint();

        } else if (penIsUp == true) {
            penY = penY - distance;

        }
    }

    public void moveBackward() {

        String command = userCommand.getText().toLowerCase();
        int distance = Integer.parseInt(command.replace("backward ", ""));

        userCommand.setText("");

        if (penIsUp == false) {
            graphics.drawLine(penColour, penX, penY, penX, (penY + distance));
            graphics.repaint();
            penY = penY + distance;

        } else if (penIsUp == true) {
            penX = penX + distance;
        }

    }

    public void penUp() {
        penIsUp = true;
        userCommand.setText("");
    }

    public void penDown() {
        penIsUp = false;
        userCommand.setText("");
    }

    class ButtonListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {

            if (userCommand.getText().equalsIgnoreCase("something")) {

                System.out.println("you typed something");
                userCommand.setText("");
            }

            else if (userCommand.getText().equalsIgnoreCase("turnleft")) {
                currentDirection = currentDirection - 1;
                if (currentDirection == -1) {
                    currentDirection = 3;
                }
                userCommand.setText("");

            }

            else if (userCommand.getText().equalsIgnoreCase("turnright")) {
                currentDirection = currentDirection + 1;
                if (currentDirection == 4) {
                    currentDirection = 0;
                }
                userCommand.setText("");
            }

            else if (userCommand.getText().startsWith("forward ")) {

                try {
                    moveForward();

                } catch (NumberFormatException e1) {
                    System.out.println("Invalid command");
                }
            }

            else if (userCommand.getText().startsWith("backward ")) {

                try {
                    moveBackward();
                }

                catch (NumberFormatException e1) {
                    System.out.println("Invalid command");
                }
            }

            else if (userCommand.getText().equalsIgnoreCase("black")) {

                penColour = Color.BLACK;
                userCommand.setText("");
            }

            else if (userCommand.getText().equalsIgnoreCase("green")) {

                penColour = Color.GREEN;
                userCommand.setText("");

            }

            else if (userCommand.getText().equalsIgnoreCase("red")) {

                penColour = Color.RED;
                userCommand.setText("");
            }

            else if (userCommand.getText().equalsIgnoreCase("reset")) {

                graphics.clear();
                penX = 0;
                penY = 0;
                userCommand.setText("");
                graphics.repaint();

            }

            else if (userCommand.getText().equalsIgnoreCase("penUp")) {
                penUp();
                userCommand.setText("");
            }

            else if (userCommand.getText().equalsIgnoreCase("penDown")) {
                penDown();
                userCommand.setText("");
            }

        }
    }
}

GraphicsPanel:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;

import javax.swing.JPanel;


@SuppressWarnings("serial")
public class GraphicsPanel extends JPanel {

    /**
     * The default BG colour of the image.
     */
    private final static Color BACKGROUND_COL = Color.DARK_GRAY;

    /**
     * The underlying image used for drawing. This is required so any previous
     * drawing activity is persistent on the panel.
     */
    private BufferedImage image;

    public GraphicsPanel() {

        Dimension resolution = Toolkit.getDefaultToolkit().getScreenSize();

        int width = (int) resolution.getWidth(); // casting the screen width to
                                                    // integer
        int height = (int) resolution.getHeight(); // casting the scren height
                                                    // to integer

        image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // Set max size of the panel, so that is matches the max size of the
        // image.
        setMaximumSize(new Dimension(image.getWidth(), image.getHeight()));

        clear();

    }

    public void drawLine(Color color, int x1, int y1, int x2, int y2) {

        Graphics g = image.getGraphics();
        g.setColor(color);
        g.translate(getWidth() / 2, getHeight() / 2);

        g.drawLine(x1, y1, x2, y2);
    }

    /**
     * Clears the image contents.
     */
    public void clear() {

        Graphics g = image.getGraphics();

        g.setColor(BACKGROUND_COL);

        g.fillRect(0, 0, image.getWidth(), image.getHeight());

    }

    @Override
    public void paint(Graphics g) {

        // render the image on the panel.
        g.drawImage(image, 0, 0, null);
    }

}   

Where possible I would also like to be able to add a scroller so that when my drawing goes outside of the graphicspanel it creates a scroller however adding a scroller didn't seem to work for that.

Any help and direction appreciated.

Edit:

    item1.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            clear();

        }

    });

Answer 1

Add an ActionListener (or use a lambda expression if you are on Java 8 or newer) to your new-button and there call the clear() method.

Besides that, you should not override paint() but paintComponent() .

And to get the JScrollPane working correctly, you need to set the preferred size of your panel, either by calling setPreferredSize() if the content sizes changes, or maybe by overriding getPreferredSize() . Furthermore you need to get the JScrollPane to recalculate whether scrollbars are necessary after the preferred size of your panel changed, thus you have to call revalidate() on your panel after the preferred size changed.