Java编程之图形化写字板

问题描述：请使用Java编程语言实现图形化的写字板，能够完成写字寄存和擦除的功能。

程序源码：

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.io.*;
import javax.swing.*;
import javax.swing.text.*;

public class JNotePadUI extends JPanel 
{
	// 变量定义
	JTextArea jta = new JTextArea("", 24, 40);
	JScrollPane jsp = new JScrollPane(jta);
	// 菜单条
	JMenuBar jmb = new JMenuBar();
	JMenu file = new JMenu("文件(F)", true);
	JMenu edit = new JMenu("编辑(E)", true);
	JMenu help = new JMenu("帮助(H)", true);
	// 工具条
	JToolBar toolBar = new JToolBar();
	// 菜单内容
	JMenuItem jmi;
	// 实例化剪切板
	Clipboard clipbd = getToolkit().getSystemClipboard();
	String text = "";

	// 构造函数
	public JNotePadUI() 
	{
		class newL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				jta.setDocument(new PlainDocument());
			}
		}
		// 打开功能
		class openL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				JFileChooser fc = new JFileChooser();
				int returnVal = fc.showDialog(JNotePadUI.this, "打开");
				if (returnVal == JFileChooser.APPROVE_OPTION) 
				{
					String file = fc.getSelectedFile().getPath();
					if (file == null) 
					{
						return;
					}
					// 读取文件
					try 
					{
						Reader in = new FileReader(file);
						char[] buff = new char[4096];
						int nch;
						while ((nch = in.read(buff, 0, buff.length)) != -1) 
						{
							jta.setDocument(new PlainDocument());
							jta.append(new String(buff, 0, nch));
						}
					} 
					catch (IOException io) 
					{
						System.err.println("IOException: " + io.getMessage());
					}
				} 
				else 
				{
					return;
				}
			}
		}
		// 保存文件
		class saveL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				JFileChooser fc = new JFileChooser();
				int returnVal = fc.showSaveDialog(JNotePadUI.this);
				if (returnVal == JFileChooser.APPROVE_OPTION) 
				{
					String savefile = fc.getSelectedFile().getPath();
					if (savefile == null) 
					{
						return;
					} 
					else 
					{
						String docToSave = jta.getText();
						if (docToSave != null) 
						{
							FileOutputStream fstrm = null;
							BufferedOutputStream ostrm = null;
							try 
							{
								fstrm = new FileOutputStream(savefile);
								ostrm = new BufferedOutputStream(fstrm);
								byte[] bytes = null;
								try 
								{
									bytes = docToSave.getBytes();
								} 
								catch (Exception e1) 
								{
									e1.printStackTrace();
								}
								ostrm.write(bytes);
							} 
							catch (IOException io) 
							{
								System.err.println("IOException: "+ io.getMessage());
							} 
							finally 
							{
								try 
								{
									ostrm.flush();
									fstrm.close();
									ostrm.close();
								} 
								catch (IOException ioe) 
								{
									System.err.println("IOException: "+ ioe.getMessage());
								}
							}
						}
					}
				} 
				else 
				{
					return;
				}
			}
		}
		
		// 退出
		class exitL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				System.exit(0);
			}
		}
		// 复制
		class copyL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				String selection = jta.getSelectedText();
				StringSelection clipString = new StringSelection(selection);
				clipbd.setContents(clipString, clipString);
			}
		}
		// 剪切
		class cutL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				String selection = jta.getSelectedText();
				StringSelection clipString = new StringSelection(selection);
				clipbd.setContents(clipString, clipString);
				jta.replaceRange("", jta.getSelectionStart(), jta.getSelectionEnd());
			}
		}
		// 粘贴
		class pasteL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				Transferable clipData = clipbd.getContents(JNotePadUI.this);
				try 
				{
					String clipString = (String) clipData.getTransferData(DataFlavor.stringFlavor);
					jta.replaceRange(clipString, jta.getSelectionStart(), jta.getSelectionEnd());
				} 
				catch (Exception ex)
				{
					
				}
			}
		}
		// 删除
		class deleteL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				jta.replaceRange("", jta.getSelectionStart(), jta.getSelectionEnd());
			}
		}
		//帮助
		class help_h implements ActionListener
		{
			public void actionPerformed(ActionEvent e)
			{
				JOptionPane.showMessageDialog(jta,"写字板支持拖入文本读取\n" + "由于对编码不熟悉做得\n不是很好 \n ", "帮助主题", JOptionPane.INFORMATION_MESSAGE);
			}
		}
		//关于
		class help_a implements ActionListener
		{
			public void actionPerformed(ActionEvent e)
			{
				JOptionPane.showMessageDialog(jta,"有不懂的地方联系\n" + "   " + "     JAVA图形界面练习\n", "关于记事本", JOptionPane.INFORMATION_MESSAGE);
			}
		}
		// 事件监听
		class jtaL implements ActionListener 
		{
			public void actionPerformed(ActionEvent e) 
			{
				
			}
		}
		// 快捷键设置
		file.add(jmi = new JMenuItem("新建N", 'N'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N, InputEvent.CTRL_MASK));
		jmi.addActionListener(new newL());
		
		file.add(jmi = new JMenuItem("打开O", 'O'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O, InputEvent.CTRL_MASK));
		jmi.addActionListener(new openL());
		
		file.add(jmi = new JMenuItem("保存S", 'S'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S, InputEvent.CTRL_MASK));
		jmi.addActionListener(new saveL());
		file.addSeparator();
		
		file.add(jmi = new JMenuItem("退出E", 'E'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_E, InputEvent.CTRL_MASK));
		jmi.addActionListener(new exitL());
		
		edit.add(jmi = new JMenuItem("复制C", 'C'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_C, InputEvent.CTRL_MASK));
		jmi.addActionListener(new copyL());
		
		edit.add(jmi = new JMenuItem("剪切X", 'X'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X, InputEvent.CTRL_MASK));
		jmi.addActionListener(new cutL());
		
		edit.add(jmi = new JMenuItem("粘帖V",'V'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_V, InputEvent.CTRL_MASK));
		jmi.addActionListener(new pasteL());
		
		edit.add(jmi = new JMenuItem("删除D", 'D'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_D, InputEvent.CTRL_MASK));
		jmi.addActionListener(new deleteL());
		edit.addSeparator();
		
		help.add(jmi = new JMenuItem("帮助(H)", 'H'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_H, InputEvent.CTRL_MASK));
		jmi.addActionListener(new help_h());
		
		help.add(jmi = new JMenuItem("关于(A)", 'A'));
		jmi.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_A, InputEvent.CTRL_MASK));
		jmi.addActionListener(new help_a());
		
		help.addSeparator();
		setLayout(new BorderLayout());
		file.setMnemonic('F');
		edit.setMnemonic('E');
		help.setMnemonic('H');
		jmb.add(file);
		jmb.add(edit);
		jmb.add(help);
		toolBar.setFloatable(true);
		add(jmb, BorderLayout.NORTH);
		add(toolBar, BorderLayout.CENTER);
		add(jsp, BorderLayout.SOUTH);

		jta.getCaret().setVisible(true);
		jta.setCaretPosition(0);
	}

	// 关闭窗口
	protected static final class appCloseL extends WindowAdapter 
	{
		public void windowClosing(WindowEvent e) 
		{
			System.exit(0);
		}
	}

	// 主函数，程序入口
	public static void main(String args[]) 
	{
		JFrame f = new JFrame();
		JNotePadUI applet = new JNotePadUI();
		f.setTitle("写字板");
		f.setBackground(Color.lightGray);
		f.getContentPane().add(applet, BorderLayout.CENTER);
		f.addWindowListener(new appCloseL());
		f.setSize(800, 500);
		f.setLocation(500,170);
		f.setVisible(true);
		f.pack();
		f.setResizable(false);
	}
}