今天准备分析一个java的记事本

先附上源码:

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

public class EditorFrame extends Frame implements ActionListener
{
TextArea textArea = new TextArea();
MenuBar menuBar = new MenuBar();
Menu fileMenu = new Menu("File");
MenuItem newItem = new MenuItem("New");
MenuItem openItem = new MenuItem("Open");
MenuItem saveItem = new MenuItem("Save");
MenuItem saveAsItem = new MenuItem("Save As");
MenuItem exitItem = new MenuItem("Exit");
Menu editMenu = new Menu("Edit");
MenuItem selectItem = new MenuItem("Select All");
MenuItem copyItem = new MenuItem("Copy");
MenuItem cutItem = new MenuItem("Cut");
MenuItem pasteItem = new MenuItem("Paste");
String fileName = null;
Toolkit toolKit=Toolkit.getDefaultToolkit();//?
Clipboard clipBoard=toolKit.getSystemClipboard();//?

private FileDialog openFileDialog= new FileDialog(this,"Open File",FileDialog.LOAD);
private FileDialog saveAsFileDialog= new FileDialog(this,"Save File As",FileDialog.SAVE);

public EditorFrame( ) // EditorFrame initialzation
{
setTitle("NotePad");
setFont(new Font("Times New Roman",Font.PLAIN,12));
setBackground(Color.white);
setSize(400,300);
fileMenu.add(newItem);
fileMenu.add(openItem);
fileMenu.addSeparator();
fileMenu.add(saveItem);
fileMenu.add(saveAsItem);
fileMenu.addSeparator();
fileMenu.add(exitItem);
editMenu.add(selectItem);
editMenu.addSeparator();
editMenu.add(copyItem);
editMenu.add(cutItem);
editMenu.add(pasteItem);
menuBar.add(fileMenu);
menuBar.add(editMenu);
setMenuBar(menuBar);//?
add(textArea);
addWindowListener(new WindowAdapter()//添加窗体的关闭事件
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}

}
);

newItem.addActionListener(this);
openItem.addActionListener(this);
saveItem.addActionListener(this);
saveAsItem.addActionListener(this);
exitItem.addActionListener(this);
selectItem.addActionListener(this);
copyItem.addActionListener(this);
cutItem.addActionListener(this);
pasteItem.addActionListener(this);
}
public void actionPerformed(ActionEvent e)
{
Object eventSource = e.getSource();//
if(eventSource == newItem)
{
textArea.setText("");
}
else if(eventSource == openItem)
{
openFileDialog.show();
fileName = openFileDialog.getDirectory()+openFileDialog.getFile();
if(fileName != null)
readFile(fileName);
}
else if (eventSource == saveItem)
{
if(fileName != null)
writeFile(fileName);
}
else if(eventSource == saveAsItem)
{
saveAsFileDialog.show();
fileName = saveAsFileDialog.getDirectory()+saveAsFileDialog.getFile();
if (fileName!= null)
writeFile(fileName);
}
else if(eventSource == selectItem)
{
textArea.selectAll();
}
else if(eventSource == copyItem)
{
String text=textArea.getSelectedText();
StringSelection selection=new StringSelection(text);
clipBoard.setContents(selection,null);
}
else if(eventSource == cutItem)
{
String text=textArea.getSelectedText();
StringSelection selection=new StringSelection(text);
clipBoard.setContents(selection,null);
textArea.replaceRange("",textArea.getSelectionStart(),textArea.getSelectionEnd());
}
else if(eventSource == pasteItem)
{
Transferable contents=clipBoard.getContents(this);
if(contents==null) return;
String text;
text="";
try{
text=(String)contents.getTransferData(DataFlavor.stringFlavor);
}catch(Exception exception){ }
textArea.replaceRange(text,textArea.getSelectionStart(),textArea.getSelectionEnd());
}
else if(eventSource == exitItem)
{
System.exit(0);
}
}

public void readFile(String fileName)
{
try{
File file = new File(fileName);
FileReader readIn = new FileReader(file);
int size = (int)file.length();
int charsRead = 0;
char[] content = new char[size];
while(readIn.ready())
charsRead += readIn.read(content, charsRead, size - charsRead);
readIn.close();
textArea.setText(new String(content, 0, charsRead));
}catch(IOException e)
{
System.out.println("Error opening file");
}
}
public void writeFile(String fileName)
{
try{
File file = new File (fileName);
FileWriter writeOut = new FileWriter(file);
writeOut.write(textArea.getText());
writeOut.close();
}catch(IOException e)
{
System.out.println("Error writing file");
}
}
public static void main(String[] args)
{
Frame frame = new EditorFrame();
frame.show();
}
}
本程序的主要按如下思路编写的:1初始化一个编辑框的类,在其中添加需要用到的控件.2在编辑框中添加各个需要用到的各个组件,事实上在第一步中只是一个组件声明,在这一步中才为组件分配内存空间.在本步中实现窗体的关闭功能.3添加各个组件的事件.实现各自的功能.4实现编辑本的的输入输出功能.5设立mainmethord.
MenuBar:是一个菜单条,但是不能直接用,先离开了,以后会继续写