Android应用中怎么对SDCARD文件进行遍历

private String mResult = new String(); private String[] mFileList = null;

File flist = new File("/mnt/sdcard");
  mFileList = flist.list();
  for(String str: mFileList){
    mResult += str;
    mResult += "\n";
  }
TextView tv = (TextView)findViewById(R.id.result);
tv.setText(mResult.toString());

FilenameFilter fnf = new FilenameFilter(){
    public boolean accept(File dir, String filename) {
      if(filename.endsWith(".mp3")) return true;
      return false;
    }
  };

  mFileList = flist.list(fnf);

  for(String str: mFileList){
    mResult += str;
    mResult += "\n";
  }

FileFilter ff = new FileFilter(){
    public boolean accept(File pathname) {
      return pathname.isDirectory();
    }
  };
File[] fileDir = flist.listFiles(ff);
for (int i = 0; i < fileDir.length; i++) {
    String str = fileDir[i].getName();
    mResult += str;
    mResult += "\n";
  }