java swing 记事本

//面板容器    和 JPanel 不是个一个东西 //边界内容管理器 到底是什么 ？？ package com.NotePad;import java.awt.BorderLayout;import java.awt.Container;import java.awt.Dimension;import java.awt.FileDialog;import java.awt.Frame;import java.awt.Toolkit;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.JButton;import javax.swing.JDialog;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.JMenu;import javax.swing.JMenuBar;import javax.swing.JMenuItem;import javax.swing.JOptionPane;import javax.swing.JPanel;import javax.swing.JScrollPane;import javax.swing.JTextArea;public class NotePad {    public static void main(String[] args) {        MyFrame notepad = new MyFrame("记事本");    }}class MyFrame extends JFrame{ // 默认边界布局管理器    private JTextArea tv_area = null;    private JScrollPane s_pane = null;//带滚动条的面板    private JMenuBar mb = null;//菜单栏    private JMenu m_file = null;//文件菜单    private JMenu m_help = null;//帮助菜单    private JMenuItem item_new = null;//新建    private JMenuItem item_open = null;//打开    private JMenuItem item_exit = null;//退出    private JMenuItem item_about = null;//关于    public MyFrame(String title){        super(title);        init();        resigerListener();    }    // 初始化相关组件    private void init() {      tv_area = new JTextArea();      s_pane = new JScrollPane(tv_area);      s_pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);//当内容超过窗体长度时出现水平滚动条      Container cpane = this.getContentPane();//得到的是一个面板容器    和 JPanel 不是个一个东西       cpane.add(s_pane,BorderLayout.CENTER);//添加到中央      this.setSize(500, 300);//设置窗体大小      // 初始化菜单      mb = new JMenuBar();      m_file = new JMenu("文件");      item_new = new JMenuItem("新建");      item_open = new JMenuItem("打开");      item_exit = new JMenuItem("退出");      m_file.add(item_new);      m_file.add(item_open);      m_file.add(item_exit);      m_help = new JMenu("帮助");      item_about = new JMenuItem("关于");      m_help.add(item_about);      mb.add(m_file);      mb.add(m_help);      // 把菜单栏添加到窗体中      this.setJMenuBar(mb);      this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//关闭窗口的时候退出应用程序      //设置窗口居中显示      //定义一个工具包      Toolkit kit = Toolkit.getDefaultToolkit();//获得屏幕大小尺寸      Dimension screenSize = kit.getScreenSize();      int screenWidth = screenSize.width;//获得屏幕宽度      int screenHeight = screenSize.height;//获得屏幕高度;      int i = this.getWidth();//获得当前窗体的宽度      int j = this.getHeight();//获得当前窗体的高度      this.setLocation((screenWidth-i)/2, (screenHeight-j)/2);      this.setVisible(true);//显示窗体    }    // 给相关组件设置事件监听器    private void resigerListener(){//委托监听器接口的实现类对象处理        item_new.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent e) {                newFile();            }        });        item_open.addActionListener(new ActionListener() {            @Override            public void actionPerformed(ActionEvent e) {                openFile();            }        });        item_exit.addActionListener(new ActionListener() {            @Override            public void actionPerformed(ActionEvent e) {                exit();            }        });        item_about.addActionListener(new ActionListener() {            @Override            public void actionPerformed(ActionEvent e) {                new AboutDialog(MyFrame.this, "关于-记事本", true);            }        });    }    //新建的功能    private void newFile(){        if(!tv_area.getText().equals("")) {            int res = JOptionPane.showConfirmDialog(null, "是否保存?","提示信息",JOptionPane.YES_NO_CANCEL_OPTION);            if(res==JOptionPane.YES_OPTION) {                //弹出文件保存对话框 JDK 自带的功能                FileDialog fd = new FileDialog(this,"保存文件",FileDialog.SAVE);                fd.setVisible(true);            }else{                tv_area.setText("");            }        }    }    //打开文件    private void openFile(){        FileDialog fd = new FileDialog(this,"打开文件",FileDialog.LOAD);        fd.setVisible(true);    }    private void exit(){        newFile();        System.exit(0);    }}class AboutDialog extends JDialog{    private JLabel desc = null;    private JPanel panel = null;    private JButton btn = null;    public AboutDialog(Frame frame,String title,boolean model){        super(frame,title,model);        init();        resigerListener();    }    private void init() {        desc = new JLabel();        desc.setText("<html>这是一个自定义的记事本，开发初期阶段，还请<br/>大家多多指教</html>");        desc.setHorizontalAlignment(JLabel.CENTER);        panel = new JPanel();        btn = new JButton("OK");        panel.add(btn);        this.add(desc);//默认放在边界内容管理器的中间        this.add(panel,BorderLayout.SOUTH);        this.setSize(300, 200);    }    private void resigerListener() {        btn.addActionListener(new ActionListener() {            @Override            public void actionPerformed(ActionEvent e) {                AboutDialog.this.dispose();//退出对话框            }        });        //设置窗口居中显示          //定义一个工具包          Toolkit kit = Toolkit.getDefaultToolkit();//获得屏幕大小尺寸          Dimension screenSize = kit.getScreenSize();          int screenWidth = screenSize.width;//获得屏幕宽度          int screenHeight = screenSize.height;//获得屏幕高度;          int i = this.getWidth();//获得当前窗体的宽度          int j = this.getHeight();//获得当前窗体的高度          this.setLocation((screenWidth-i)/2, (screenHeight-j)/2);        this.setVisible(true);    }}