The FileConnection API specified in JSR-75 gives Access to the local file systems on devices like PDA. In order to overcome security issues MIDlet needs to include requested file permission in its JAD file under MIDLet-Permission property.The example below has a file browser to move around the file system, select and read images stored in its local image Directory.
import Java.util.*;
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.io.file.*;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class FileMidlet extends MIDlet implements CommandListener
{
private String currDirName;
private Command view = new Command("View", Command.ITEM, 1);
private Command back = new Command("Back", Command.BACK, 2);
private Command exit = new Command("Exit", Command.EXIT, 3);
private final static String UP_DIRECTORY = "..";
private final static String MEGA_ROOT = "/";
private final static String SEP_STR = "/";
private final static char SEP = '/';
public FileMidlet()
{
currDirName = MEGA_ROOT;
}
public void startApp()
{
boolean isAPIAvailable = false;
if (System.getProperty(
"microedition.io.file.FileConnection.version") != null)
{
isAPIAvailable = true;
try
{
showCurrDir();
}
catch (SecurityException e)
{}
catch (Exception e) {}
}
else
{
StringBuffer splashText = new StringBuffer(
getAppProperty("MIDlet-Name")).append("\n").append(
getAppProperty("MIDlet-Vendor")).
append(isAPIAvailable?"":"\nFileConnection API not available");
Alert splashScreen = new Alert(null,splashText.toString(),
null,AlertType.INFO);
splashScreen.setTimeout(3000);
Display.getDisplay(this).setCurrent(splashScreen);
}
}
public void pauseApp() {}
public void destroyApp(boolean cond)
{
notifyDestroyed();
}
public void commandAction(Command c, Displayable d)
{
if (c == view)
{
List curr = (List)d;
final String currFile = curr.getString(curr.getSelectedIndex());
new Thread(new Runnable()
{
public void run()
{
if (currFile.endsWith(SEP_STR)
currFile.equals(UP_DIRECTORY))
{
traverseDirectory(currFile);
} else
{
showFile(currFile);
}
}
}).start();
}
else if (c == back)
{
showCurrDir();
}
else if (c == exit)
{
destroyApp(false);
}
}
void showCurrDir()
{
Enumeration e;
FileConnection currDir = null;
List browser;
try
{
if (MEGA_ROOT.equals(currDirName))
{
e = FileSystemRegistry.listRoots();
browser = new List(currDirName, List.IMPLICIT);
}
else
{
currDir = (FileConnection)Connector.open(
"file://localhost/" + currDirName);
e = currDir.list();
browser = new List(currDirName, List.IMPLICIT);
browser.append(UP_DIRECTORY);
}
while (e.hasMoreElements())
{
String fileName = (String)e.nextElement();
if (fileName.charAt(fileName.length()-1) == SEP)
{
browser.append(fileName);
}
else
{
browser.append(fileName);
}
}
browser.setSelectCommand(view);
browser.addCommand(exit);
browser.setCommandListener(this);
if (currDir != null)
{
currDir.close();
}
Display.getDisplay(this).setCurrent(browser);
}
catch (IOException ioe)
{}
}
void traverseDirectory(String fileName)
{
if (currDirName.equals(MEGA_ROOT))
{
if (fileName.equals(UP_DIRECTORY))
{
// can not go up from MEGA_ROOT
return;
}
currDirName = fileName;
}
else if (fileName.equals(UP_DIRECTORY))
{
// Go up one directory
// TODO use setFileConnection when implemented
int i = currDirName.lastIndexOf(SEP, currDirName.length()-2);
if (i != -1)
{
currDirName = currDirName.substring(0, i+1);
}
else
{
currDirName = MEGA_ROOT;
}
}
else
{
currDirName = currDirName + fileName;
}
showCurrDir();
}
void showFile(String fileName)
{
try
{
FileConnection fc = (FileConnection)
Connector.open("file://localhost/" + currDirName + fileName);
if (!fc.exists())
{
throw new IOException("File does not exists");
}
InputStream fis = fc.openInputStream();
byte[] b = new byte[1024];
int length = fis.read(b, 0, 1024);
fis.close();
fc.close();
TextBox tb = new TextBox("View File: " + fileName, null, 1024,
TextField.ANY TextField.UNEDITABLE);
tb.addCommand(back);
tb.addCommand(exit);
tb.setCommandListener(this);
if (length > 0)
{
tb.setString(new String(b, 0, length));
}
Display.getDisplay(this).setCurrent(tb);
}
catch (Exception e) {}
}
}
（出处：http://www.knowsky.com）