android 之檔案下載的實現思路

    從網上下載檔案,寫入sd卡.思路如下:
    1.建立一個http訪問
        HttpURLConnection httpcon=(HttpURLConnection)url.openConnection()
    2.從HttpURLConnection中擷取一個輸入資料流
        InputStream httpInputStream=httcon.getInputStream()
    3.解析流
        一般用BufferedReader來擷取.
        BufferedReader bfReader=new BufferedReader(new InputSreamReader(InputSream in))
        String line=bfReader.readLine();
    4.建立檔案,產生對應的writer
        File fileWrite=new File(localPath);
        FileOutputStream fstream=new FileOutputStream(fileWrite);
        BufferedWriter bfWriter=new BufferedWriter(new OutputStreamWriter(fstream));
        bfWriter.writer(line,0,line.length())
    5.最後記得關閉流的reader和writer
   
    如果是非文字檔的話,最好還是按位元組來讀取和寫入.

    最後,需要注意的是,要在android manifest.xml中定義使用者權限
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>