从 Internet 下载的 android 文件出现异常

Question

我正在尝试从 Internet 下载文件。我已授予所有权限。但我的应用程序给出了一些异常(exception)。这是我的源代码............

  private void write()
        {


            try {
               URL url = new URL("http://wordpress.org/plugins/about/readme.txt");
                // URL url = new URL("http://androidsaveitem.appspot.com/downloadjpg");
                HttpURLConnection c = (HttpURLConnection) url.openConnection();
                c.setRequestMethod("GET");

             //  c.setReadTimeout(10000); // millis
             //  c.setConnectTimeout(15000); // millis

                c.setDoOutput(true);


              c.connect();

                String PATH = Environment.getExternalStorageDirectory()
                        + "/download/";

                File file = new File(PATH);
                file.mkdirs();

                String fileName = "Sap.txt";


                File outputFile = new File(file, fileName);
                FileOutputStream fos = new FileOutputStream(outputFile);

                InputStream is = c.getInputStream();

                byte[] buffer = new byte[1024];
                int len1 = 0;
                while ((len1 = is.read(buffer)) != -1) {

                    fos.write(buffer, 0, len1);

                }
                fos.close();
                is.close();

                // }
            } catch (IOException e) {
                MessageBox(e.getMessage());
            }

        }



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

c.connect();//这个 connect() 函数给出了一个异常。我无法确定问题所在。

请有人帮助我......

Answer 1

在main函数中添加

new AsyncTaskRunner().execute("");

在main函数后面添加

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

            @Override
            protected void onPostExecute(String result) {
                    try
                    {

                        MessageBox(result);

                        /*
                        String PATH = Environment.getExternalStorageDirectory()
                                + "/download/";

                        File file = new File(PATH);
                        file.mkdirs();

                        String fileName = "Sap.txt";

                        File outputFile = new File(file, fileName);
                        FileOutputStream fos = new FileOutputStream(outputFile);

                        InputStream is = c;

                        byte[] buffer = new byte[1024];
                        int len1 = 0;
                        while ((len1 = is.read(buffer)) != -1) {

                            fos.write(buffer, 0, len1);

                        }
                        fos.close();
                        is.close();
                        */
                    }
                    catch(Exception ex)
                    {
                        MessageBox(ex.getMessage()+"error ");
                    }

            }

            @Override
            protected String doInBackground(String... params) {
                try
                {
                    URL url = new URL("http://wordpress.org/plugins/about/readme.txt");
                    // URL url = new
                    // URL("http://androidsaveitem.appspot.com/downloadjpg");
                    HttpURLConnection c = (HttpURLConnection) url.openConnection();
                    c.setRequestMethod("GET");

                    // c.setReadTimeout(10000); // millis
                    // c.setConnectTimeout(15000); // millis

                    //c.setDoOutput(true);

                    c.connect();
                    InputStream is = c.getInputStream();

                    String PATH = Environment.getExternalStorageDirectory()
                            + "/download/";

                    File file = new File(PATH);
                    file.mkdirs();

                    String fileName = "Sap.txt";

                    File outputFile = new File(file, fileName);
                    FileOutputStream fos = new FileOutputStream(outputFile);

                    //InputStream is = c;

                    byte[] buffer = new byte[1024];
                    int len1 = 0;
                    while ((len1 = is.read(buffer)) != -1) {

                        fos.write(buffer, 0, len1);

                    }
                    fos.close();
                    is.close();

                    Log.v("esty", "Successfully");

                    return "Successfully";
                }
                catch(Exception ex)
                {
                    Log.v("esty", ex.getMessage());
                    return "failed"+ex.getMessage();
                }
            }

希望能解决你的问题! :)