在SD卡讀寫

    		//MEDIA_UNKNOWN:不能識別sd卡
    		//MEDIA_REMOVED:沒有sd卡
    		//MEDIA_UNMOUNTED:sd卡存在但是沒有掛載
    		//MEDIA_CHECKING:sd卡正在準備
    		//MEDIA_MOUNTED：sd卡已經掛載，可用
    		if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
    		
	    		//返回一個File對象，其路徑是sd卡的真實路徑 
	    		File file = new File(Environment.getExternalStorageDirectory(), "info.txt");
	//    		File file = new File("sdcard/info.txt");
	    		FileOutputStream fos;
				try {
					fos = new FileOutputStream(file);
					fos.write((name + "##" + pass).getBytes());
					fos.close();
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
    		}
    		else{
    			Toast.makeText(this, "sd卡不可用喲親麼麼噠", 0).show();
    		}