android - 下载 XML 文件时出现异常

Question

我正在开发一个 Android 应用程序，我正在尝试从该 URL 下载 XML 文件http://data.gov.in/sites/default/files/Date-Wise-Prices-all-Commodity.xml并尝试将此文件保存到我的 sd 卡中。

单击按钮时，我想下载文件。所以，我在我的按钮点击上使用以下代码..

try
    {
        URL url = new URL("http://data.gov.in/sites/default/files/Date-Wise-Prices-all-Commodity.xml");

        //create the new connection

        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

        //set up some things on the connection

        urlConnection.setRequestMethod("GET");

        urlConnection.setDoOutput(true);

        //and connect!

        urlConnection.connect();

        //set the path where we want to save the file

        //in this case, going to save it on the root directory of the

        //sd card.

        File SDCardRoot = new File("/sdcard/"+"XML_folder/");

        //create a new file, specifying the path, and the filename

        //which we want to save the file as.

        File file = new File(SDCardRoot,"webservice.xml");

        //this will be used to write the downloaded data into the file we created

        FileOutputStream fileOutput = new FileOutputStream(file);

        //this will be used in reading the data from the internet

        InputStream inputStream = urlConnection.getInputStream();

        //this is the total size of the file

        int totalSize = urlConnection.getContentLength();

        //variable to store total downloaded bytes

        int downloadedSize = 0;

        //create a buffer...

        byte[] buffer = new byte[1024];

        int bufferLength = 0; //used to store a temporary size of the buffer

        //now, read through the input buffer and write the contents to the file

        while ( (bufferLength = inputStream.read(buffer)) > 0 ) 

        {

        //add the data in the buffer to the file in the file output stream (the file on the sd card

        fileOutput.write(buffer, 0, bufferLength);

        //add up the size so we know how much is downloaded

        downloadedSize += bufferLength;

        int progress=(int)(downloadedSize*100/totalSize);

        //this is where you would do something to report the prgress, like this maybe

        //updateProgress(downloadedSize, totalSize);

        }

        //close the output stream when done

        fileOutput.close();
    }
    catch(Exception e)
    {
        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
    }

因为我已经使用try and catch它捕获异常并向我显示此消息data.gov.in (java.net.UnknownHostException: data.gov.in)

那么，现在该怎么办？

Answer 1

检查您的清单文件，是否授予权限，并使用 AsyncTask 或线程概念进行 url 连接（后台工作）。

         ibut.setOnClickListener(new View.OnClickListener() 
        {
       public void onClick(View v) 
          {
            new Thread(new Runnable() 
                {
                  public void run() 
                    {
                try
                 {
                     //http connection code. 
                 }      
                          catch(Exception e) 
                         {
                        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_SHORT).show(); 
                         }

                }).start();


        }}); 

Answer 2

此错误即将到来

1. <uses-permission android:name="android.permission.INTERNET"/>如果你忘了写这个
2. 如果您的互联网速度很慢或无法正常工作
3. 最后，如果您的服务器出于任何原因没有响应您的请求。

Answer 3

尝试这个..

URL url = new URL(Your URL);

                //create the new connection

                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

                //set up some things on the connection

                urlConnection.setRequestMethod("GET");

                urlConnection.setDoOutput(true);

                //and connect!

                urlConnection.connect();

                //set the path where we want to save the file

                //in this case, going to save it on the root directory of the

                //sd card.

                File SDCardRoot = new File("/sdcard/");

                //create a new file, specifying the path, and the filename

                //which we want to save the file as.

                File file = new File(SDCardRoot,"hello.xml");

                //this will be used to write the downloaded data into the file we created

                FileOutputStream fileOutput = new FileOutputStream(file);

                //this will be used in reading the data from the internet

                InputStream inputStream = urlConnection.getInputStream();

                //this is the total size of the file

                int totalSize = urlConnection.getContentLength();

                //variable to store total downloaded bytes

                int downloadedSize = 0;

                //create a buffer...

                byte[] buffer = new byte[1024];

                int bufferLength = 0; //used to store a temporary size of the buffer

                //now, read through the input buffer and write the contents to the file

                while ( (bufferLength = inputStream.read(buffer)) > 0 ) 

                {

                //add the data in the buffer to the file in the file output stream (the file on the sd card

                fileOutput.write(buffer, 0, bufferLength);

                //add up the size so we know how much is downloaded

                downloadedSize += bufferLength;

                int progress=(int)(downloadedSize*100/totalSize);

                //this is where you would do something to report the prgress, like this maybe

                //updateProgress(downloadedSize, totalSize);

                }

                //close the output stream when done

                fileOutput.close();

Answer 4

将权限放入清单文件

<uses-permission android:name="android.permission.INTERNET"/>

试试这个代码找不到文件

//set the path where we want to save the file

    //in this case, going to save it on the root directory of the

    //sd card.

    File SDCardRoot = new File("/sdcard/"+"XML_folder/");

    if(SDCardRoot.exists() == false){
         SDCardRoot.mkdirs();  
    }

    //create a new file, specifying the path, and the filename

    //which we want to save the file as.

    File file = new File(SDCardRoot,"webservice.xml");