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("这是一个自定义的记事本，开发初期阶段，还请
大家多多指教");
        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);
    }
}