AWT实现的一个简单文本显示程序

在这个例子中，我们使用了Java中的awt包来实现可视化的功能，然后可以把一个文件的内容显示出来。里面用到了IO的知识，还有可视化的一些内容。这个例子，我们只要想说的就是IO部分，至于可视化，不是重点。

package chapter03;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class FileViewer extends Frame implements ActionListener{
	
	String directory;
	TextArea textarea;
	public FileViewer(){
		this(null,null);
	}	
	public FileViewer(String directory,String filename){
		super();
                  //添加窗体关闭事件
		addWindowListener(new WindowAdapter(){
			public void windowClosing(WindowEvent e){
				System.exit(0);
			}
		});
		textarea=new TextArea("",24,80);
		textarea.setFont(new Font("MonoSpaced",Font.PLAIN,12));
		textarea.setEditable(false);
		this.add("Center",textarea);
		Panel p=new Panel();
		p.setLayout(new FlowLayout(FlowLayout.RIGHT,10,5));
		this.add(p,"South");
		
		Font font=new Font("SansSerif",Font.BOLD,14);
		Button openfile=new Button("open file");
		Button close=new Button("close");
		openfile.addActionListener(this);
		openfile.setActionCommand("open");
		openfile.setFont(font);
		close.addActionListener(this);
		close.setActionCommand("close");
		close.setFont(font);
		p.add(openfile);
		p.add(close);
		this.pack();
		if(directory==null){
			File f;
			if((filename!=null) && (f=new File(filename)).isAbsolute()){
				directory=f.getParent();
				filename=f.getName();
			}else{
				directory=System.getProperty("user.dir");
			}
		}
		this.directory=directory;
		setFile(directory,filename);
	}
	
	public void setFile(String directory,String filename){
		if((filename==null)|| (filename.length()==0)){
			return ;
		}
		File f;
		FileReader in=null;
		try{
			f=new File(directory,filename);
			in=new FileReader(f);
                           //定义一个数组
			char [] buffer=new char[4096];
			int len;
			textarea.setText(" ");
                            //读取文件
			while((len=in.read(buffer))!=-1){
				//System.out.println(len);
				String msg=new String(buffer,0,len);
                                     //将读取出来的内容添加到窗体上
				textarea.setText(msg);
			}
			this.setTitle("FileViewer: "+filename);
			textarea.setCaretPosition(0);
		}catch(IOException e){
			textarea.setText(e.getClass().getName()+" : "+e.getMessage());
			this.setTitle("FileViewer :"+filename+" :I/O Exception");
		}finally{
			if(in!=null){
				try {
					in.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		
	}
	
	public void actionPerformed(ActionEvent e) {
		String cmd=e.getActionCommand();
		if(cmd.equals("open")){
			FileDialog f=new FileDialog(this,"Open File",FileDialog.LOAD);
			f.setDirectory(directory);
			f.setVisible(true);
			directory=f.getDirectory();
			setFile(directory,f.getFile());
			f.dispose();
		}else if(cmd.equals("close")){
			System.exit(0);
		}
	}

	public static void main(String [] args)throws IOException{
		FileViewer f=new FileViewer("e:\\java\\","Hello.java");
		f.setVisible(true);
	}
}

不错！