Question

我有一个网址，我必须从中下载一个xls文件。我发布编码数据，响应将是一个xls文件。但我不确定如何将此xls文件下载到我的外部存储。当我运行网络电话时，我得到了一个 java.io.FileNotFoundException

它说

Attempt to invoke virtual method 'void java.io.BufferedReader.close()' on a null object reference

我不知道如何将响应作为文件获取。这是我的代码。

try{
        // TODO Auto-generated method stub
        String data=URLEncoder.encode("job_id","UTF-8")
                +"="+URLEncoder.encode(String.valueOf(responseText),"UTF-8");
        data+="&"+URLEncoder.encode("m_id","UTF-8")+"="
                +URLEncoder.encode(logedinUserId,"UTF-8");
        data+="&"+URLEncoder.encode("start","UTF-8")+"="
                +URLEncoder.encode(start,"UTF-8");
        data+="&"+URLEncoder.encode("end","UTF-8")+"="
                +URLEncoder.encode(endDate,"UTF-8");

        Log.e("data",""+data);

        String text="";
        BufferedReader reader=null;

        // Send data
        try{

            // Defined URL  where to send data
            URL url=new URL("url here");

            // Send POST data request

            URLConnection conn=url.openConnection();
            conn.setDoOutput(true);
            OutputStreamWriter wr=new OutputStreamWriter(conn.getOutputStream());
            wr.write(data);
            wr.flush();

            // Get the server response

            reader=new BufferedReader(new InputStreamReader(conn.getInputStream()));
            StringBuilder sb=new StringBuilder();
            String line=null;

            // Read Server Response
            while((line=reader.readLine())!=null){
                // Append server response in string
                sb.append(line+"\n");
            }


            text=sb.toString();
        }catch(Exception ex)

        {
            ex.printStackTrace();
        }finally{
            try{
                reader.close();
            }catch(Exception ex){
                ex.printStackTrace();

            }
        }

        Log.e("response x",""+text);


    }catch(UnsupportedEncodingException e){
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Answer 1

首先，您必须将下载过程放在 asyncTask 中，以便 UI线程不会被阻止。然后尝试此代码，它将帮助您下载文件。

  private class FetchFileURlFromServer extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread
     * Show Progress Bar Dialog
     */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        onCreateDialog(progress_bar_type);
    }

    /**
     * Downloading file in background thread
     */
    @SuppressWarnings("ResultOfMethodCallIgnored")
    @Override
    protected String doInBackground(String... f_url) {
        String path = "";
        int responseCode = 0;
        StringBuilder response = null;
        try {
            if (f_url[0] != null && !f_url[0].equals(""))
                f_url[0] = f_url[0].replace("your url");


            URL obj = new URL(f_url[0]);
            HttpURLConnection con = (HttpURLConnection)
                    obj.openConnection();
            con.setRequestMethod("GET");
            con.setDoOutput(true);

            BufferedReader in = new BufferedReader(new 
            InputStreamReader(con.getInputStream()));
            String inputLine;
            response = new StringBuilder();

            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();

            System.out.println("Response : -- " + response.toString());

           //              path = connection.getInputStream().toString();

        } catch (Exception e) {
          Log.e("Error: ", e.getMessage());
        }

        return response != null ? response.toString() : null;
 //            return path;
    }

    /**
     * Updating progress bar
     */
    protected void onProgressUpdate(String... progress) {
        // setting progress percentage
        progressDialogForDownload.setProgress(Integer.parseInt(progress[0]));
    }

    /**
     * After completing background task
     * Dismiss the progress dialog
     **/

    @Override
    protected void onPostExecute(String fileURL) {
        // dismiss the dialog after the file was downloaded
        if (progressDialogForDownload.isShowing() && progressDialogForDownload != null) {
            progressDialogForDownload.dismiss();
            progressDialogForDownload = null;
        }

       // you can open your file using intents or whatever you want to use.
            startActivity(browserIntent);
            Log.d("", "onButtonClickView: " + fileURL);
        }

    }
}

希望它对你有所帮助。

从URL下载文件时获取文件未找到异常

1 个答案: