如何将Jmenubar添加到mouseclick程序？

Question

I'm writing a code that display a rectangle on the mouse click and store it in arraylist and I wanted to add a menu to give the option to the user to save the shape in a file and load it.

So I combined and old menu class that I've been working on with the mouse click class and when I run, I only get an empty JFrame box with no menu and no rect appear when I click anywhere. and there's an illegalArgumentExpression in the console.

The code worked perfectly until I added the third class, so which part is wrong?

First Class:

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class MouseClick{
    private static int x,y;
    private static DrawingObjects object = new DrawingObjects();
    private static MenuDemo menu = new MenuDemo();

    public static void main(String[] args){

        JFrame frame = new JFrame("MouseClick");
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);
        frame.add(object);
        frame.add(menu);
        object.addMouseListener(new AL());
    }
    static class AL extends MouseAdapter{
        public void mouseClicked (MouseEvent e){
            x = e.getX();
            y = e.getY();
            object.drawing(x, y);
        }
    }
}

Second Class:

import javax.swing.*;
import java.awt.*;
import java.util.*;
public class DrawingObjects extends JPanel{
    private ArrayList<Point> points = new ArrayList<>();


    public void drawing(int x, int y){
        points.add(new Point(x, y));
        repaint();
    }
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        for(Point p : points){
            g.fillRect(p.x, p.y, 20, 20);

        }
    }
    }

Third Class:

import java.awt.*;
import javax.swing.*;

public class MenuDemo extends JFrame {
    JMenu mnuFile, mnuExit, mnuitemSaveAs;
    JMenuItem mnuitemNew, mnuitemSave, mnuitemDoc, mnuitemTxt, mnuitemDat;
    public MenuDemo(){
        Container container = getContentPane();
        container.setLayout(new FlowLayout());

        mnuFile = new JMenu("File");
        mnuExit = new JMenu("Exit");

        mnuitemNew = new JMenuItem("New");
        mnuitemSave = new JMenuItem("Save");
        mnuitemSaveAs = new JMenu ("Save As");

        mnuitemDoc = new JMenuItem(".doc");
        mnuitemTxt = new JMenuItem(".txt");
        mnuitemDat= new JMenuItem(".dat");

// menu bar 
        JMenuBar jmb = new JMenuBar();
        setJMenuBar(jmb);

        mnuFile.add(mnuitemNew);
        mnuFile.add(mnuitemSave);
        mnuFile.add(mnuitemSaveAs);
        mnuitemSaveAs.add(mnuitemDoc);
        mnuitemSaveAs.add(mnuitemTxt);
        mnuitemSaveAs.add(mnuitemDat);

        jmb.add(mnuFile);
        jmb.add(mnuExit);

    }
    }

Answer 1

Your MenuDemo class extends JFrame. You cannot add a JFrame to another JFrame. The main method in your MouseClick class must call frame.setJMenuBar .

I suggest you alter your MenuDemo class to store its JMenuBar in a field, just like all the menus and menu items, so other classes (like MouseClick) are able to access it.