获得sd卡中指定类型的文件

public class FileList extends Activity{
ListView filelist;
private static final String MEDIA_PATH = "/sdcard/";
List<String> txt = new ArrayList<String>();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.dialog);
filelist=(ListView)findViewById(R.id.filelist);
filelist.setOnItemClickListener(txtlistlistener);
updateTxtList();
}
public void updateTxtList() {
File home = new File(MEDIA_PATH);
if (home.listFiles(new TxtFilter()).length > 0) {
for (File file : home.listFiles(new TxtFilter())) {
txt.add(file.getName());
}
ArrayAdapter<String> adapter_txts = new ArrayAdapter<String>(this,
android.R.layout.simple_expandable_list_item_1, txt);
filelist.setAdapter(adapter_txts);
}
}
private class TxtFilter implements FilenameFilter {
@Override
public boolean accept(File dir, String name) {
// TODO Auto-generated method stub
return (name.endsWith(".txt"));
}
}
OnItemClickListener txtlistlistener = new OnItemClickListener() {

@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int position,
long id) {
// TODO Auto-generated method stub
String path = txt.get(position);
Intent intent_path = new Intent();
intent_path.setClass(FileList.this, Login.class);
Bundle bundle_path = new Bundle();
bundle_path.putString("path", MEDIA_PATH + path);
intent_path.putExtras(bundle_path);
startActivity(intent_path);
}

};