Navigation in files/directory

package com.AndroidListFiles;

import java.io.File;
import java.util.ArrayList;
import java.util.List;

import android.app.ListActivity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

public class AndroidListFilesActivity extends ListActivity {

private List<String> fileList = new ArrayList<String>();

   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
      
       File root = new File(Environment
         .getExternalStorageDirectory()
         .getAbsolutePath());
       ListDir(root);

   }
  
   @Override
protected void onListItemClick(ListView l, View v, int position, long id) {
 // TODO Auto-generated method stub
    File selected = new File(fileList.get(position));
    if(selected.isDirectory()){
     ListDir(selected);
    }else {
     Toast.makeText(AndroidListFilesActivity.this,
       selected.toString() + " selected",
       Toast.LENGTH_LONG).show();
    }
}

void ListDir(File f){
    File[] files = f.listFiles();
    fileList.clear();
    for (File file : files){
     fileList.add(file.getPath()); 
    }
   
    ArrayAdapter<String> directoryList
    = new ArrayAdapter<String>(this,
      android.R.layout.simple_list_item_1, fileList);
    setListAdapter(directoryList);
   }

}

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