List files/directory in Android

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.widget.ArrayAdapter;

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);

    }
    
    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); 
    }

}

next:
- Navigation in files/directory