listenermcard.java

J2ME程序设计实例教程的源码

import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import javax.microedition.io.file.*;
import java.util.Enumeration;
import java.io.*;
import javax.microedition.io.*;

public class ListenerMCard extends MIDlet 
                implements FileSystemListener, CommandListener {
    private List rootsList;
    private Command cmdExit = new Command("退出", Command.EXIT, 1);
    private Display display;
    
    public ListenerMCard() {
        rootsList = new List("系统根目录列表", List.IMPLICIT);
        rootsList.addCommand(cmdExit);
        rootsList.setCommandListener(this);
        
        //添加文件系统监视器
        FileSystemRegistry.addFileSystemListener(this);
    }
    
    public void startApp() {
        display = Display.getDisplay(this);
        updateList();
        display.setCurrent(rootsList);
        
        try {
            String fileUrl = "file:///root1/Phone/Hello.txt";
            FileConnection fcFile = (FileConnection)Connector.open(fileUrl);
            long size = fcFile.fileSize();
            OutputStream os = fcFile.openOutputStream(size);
            byte[] buf = "我们一起学习J2ME编程！".getBytes();
            os.write(buf, 0, buf.length);
            
            InputStream is = fcFile.openInputStream();
            byte[] buffer = new byte[240];
            int n = is.read(buffer, 0, buffer.length);
            String s = new String(buffer, 0, n);
            System.out.println(s);
            
            fcFile.close();
        }
        catch(IOException ioe) {
            System.out.println("error: "+ioe.toString());
        }

    }
    
    public void pauseApp() {
    }
    
    public void destroyApp(boolean unconditional) {
    }
    
    public void commandAction(Command cmd, Displayable d) {
        if(cmd == cmdExit) {
            notifyDestroyed();
        }
    }
    
    //文件系统监视器中的方法。如果有存储卡插拔时，监视器将调用该方法。
    //state表示存储卡状态，只能取FileSystemListener接口中定义的常量
    //rootName表示存储卡对应的文件根目录名
    public void rootChanged(int state, String rootName) {
        Alert alert = new Alert("消息", "", null, AlertType.INFO);
        if(state == FileSystemListener.ROOT_ADDED) {    //插入存储卡
            alert.setString("您插入了一个新的存储卡，映射为文件根目录：" + rootName);
        }
        else if(state == FileSystemListener.ROOT_REMOVED) {   //拔出存储卡
            alert.setString("您拔出了存储卡，对应的文件根目录\"" + 
                                rootName+ "\"从系统中删除！");
        }
        alert.setTimeout(2000);
        display.setCurrent(alert, rootsList);
        updateList();
    }
    
    private void updateList() {
        rootsList.deleteAll();
        Enumeration e = FileSystemRegistry.listRoots();
        while(e.hasMoreElements()) {
            rootsList.append((String)e.nextElement(), null);
        }
    }
}