Question

我正在尝试编写一个可以复制/粘贴并保存到txt文件的剪贴板程序。当程序有效时，我试图将按钮更改为带有MenuItems的菜单，但是，我无法弄清楚如何正确使用菜单项，因为我无法将其添加到面板。

请注意我使用的是AWT而不是Swing，所以没有JPanel / JFrame等。任何提示/帮助都表示赞赏。

这是我的代码，并尝试将其更改为菜单，请让我知道我做错了什么：

import java.awt.*;
import java.awt.event.*;
import java.io.*;

public class CheesyWP extends Frame implements ActionListener {

    /**
     * @param args
     */

    //new panel for menu
    Panel north;

    //original
    Panel center;
    Panel south;
    Button save;
    Button load;
    Button clip;
    Button finish;
    Menu mn;
    MenuItem mSave;
    MenuItem mLoad;
    MenuItem mClip;
    MenuItem mFinish;
    TextArea ta;

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        CheesyWP cwp = new CheesyWP();
        cwp.doIt();

    }

    public void doIt() {
        center = new Panel();
        south = new Panel();
        clip = new Button("Open Clipboard");
        save = new Button("Save");
        load = new Button("Load");
        finish = new Button("Finish");

        //menu items
        north = new Panel();
        mn = new Menu();
        mSave = new MenuItem("Save");
        mLoad = new MenuItem("Load");
        mClip = new MenuItem("Open Clipboard");
        mFinish = new MenuItem("Finish");
        mn.add(mSave);
        mn.add(mLoad);
        mn.add(mClip);
        mn.add(mFinish);
        mSave.addActionListener(this);
        mLoad.addActionListener(this);
        mClip.addActionListener(this);
        mFinish.addActionListener(this);
        //north.add(mn); <-------//PROBLEM HERE

        clip.addActionListener(this);
        save.addActionListener(this);
        load.addActionListener(this);
        finish.addActionListener(this);
        ta = new TextArea(20, 80);
        center.add(ta);
        south.add(load);
        south.add(save);
        south.add(clip);
        south.add(finish);
        this.add(center, BorderLayout.CENTER);
        this.add(south, BorderLayout.SOUTH);
        this.setSize(600, 300);
        this.setVisible(true);
    }

    public void actionPerformed(ActionEvent ae) {
        if (ae.getSource() == save) {
            try {
                File junk = new File("junk.txt");
                FileWriter fw = new FileWriter(junk);
                fw.write(ta.getText()); // write whole TextArea contents
                fw.close();
            } catch (IOException ioe) {
            }
        }// ends if
        if (ae.getSource() == load) {
            String temp = "";
            try {
                File junk = new File("junk.txt");
                FileReader fr = new FileReader(junk);
                BufferedReader br = new BufferedReader(fr);
                while ((temp = br.readLine()) != null) {
                    ta.append(temp + "\n");
                }
                br.close();
            } catch (FileNotFoundException fnfe) {
            } catch (IOException ioe) {
            }
        }
        if (ae.getSource() == finish) {
            System.exit(0);
        }
        if(ae.getSource()==clip){
            new ClipBoard();
        }
    }

    class ClipBoard extends Frame {
        public ClipBoard() { // a constructor
            this.setTitle("Clipboard");
            this.setLayout(new FlowLayout());
            this.add(new TextArea(10, 50));
            this.setSize(400, 160);
            this.setVisible(true);
        }
    }
}

Answer 1

this.validate();

Swing组件的默认状态为无效，除非经过验证（通过在组件本身或其中一个父容器上调用.validate（）方法），否则不会将其绘制到屏幕上。

Answer 2

只需更改此

 Panel north;

到此

MenuBar north;

因为使用awt库，你不能将菜单添加到Panel，但是你可以将菜单添加到MenuBar

Java菜单AWT进入Panel

2 个答案: