public class ListLibraryActivity extends ListActivity {
    private File sdDir;
    private File[] files;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
            sdDir = new File(Environment.getExternalStorageDirectory().getPath());
            files = sdDir.listFiles();
            ArrayAdapter<File> adapter = new ArrayAdapter<File>(this, android.R.layout.simple_list_item_1, files);
            setListAdapter(adapter);

    }