Android中如何判斷內存卡是否存在

if (Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
        {
            /* 得到SD卡得路徑 */
            mRecAudioPath = Environment.getExternalStorageDirectory();
            /* 更新所有錄音文件到List中 */
            musicList();
        }
        else
        {
            Toast.makeText(Record.this, "沒有SD卡", Toast.LENGTH_LONG).show();
        }