java 输入/输出流小记 (3)

一个简单的读取字符流，显示的例子

package cn.lokvin.examples.io;

import java.awt.Button;
import java.awt.FileDialog;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;

public class FileViewer extends Frame implements ActionListener {
	String directory; // 显示 dialog 的目录
	TextArea textarea; // 显示文件内容区域
	
	public FileViewer () {
		this(null, null);
	}
	
	public FileViewer(String fileName) {
		this(null, fileName);
	}
	
	public FileViewer(String directory, String fileName) {
		super(); //创建 Frame
		
		//添加关闭Frame 响应事件
		this.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				dispose();
			}
		});
		
	    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);
			char[] buffer = new char[4096];
			int len;
			textarea.setText("");
			
			while((len = in.read(buffer)) != -1) {
				String s = new String(buffer, 0, len);
				textarea.append(s);
			}
			
			this.setTitle("FileViewer: " + fileName);//设置窗口名称
			textarea.setCaretPosition(0);//到文件起始位置
			
		}catch(IOException e) {
			textarea.setText(e.getClass().getName() + " : " + e.getMessage());
			this.setTitle("FileViewer: " + fileName + ": I/O Exception");
		}finally {
			try {
				if(in != null) in.close();
			}catch(IOException e){}
		}
		
		
		
	}

	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);
			
			//显示对话框等待用户响应
			f.show();
			
			directory = f.getDirectory();
			setFile(directory, f.getFile());
			f.dispose();
		}else if(cmd.equals("close")) {
			this.dispose();
		}
		
		
	}
	
	public static void main(String[] args) throws IOException {
		Frame f = new FileViewer((args.length == 1 ? args[0]:null));
		
		f.addWindowListener(new WindowAdapter() {
			public void windowClosed(WindowEvent e) {
				System.exit(0);
			}
		});
		
		f.show();
	}
	
	
	

}