java - 如果多次使用，InputStream 不起作用

Question

我在使用 InputStream 时遇到了一些问题。我正在编写一个小的 Android 应用程序，其中一部分必须从网站获取 HTML 代码。一般来说，它工作正常，但有时(通常是第二次调用，但也可能需要几次尝试重现)它会跳过 InputStream(我注意到这一点，因为它在调试时需要几秒钟，但每次它失败了，它会立即跳到下一行)。任何想法可能导致此问题以及如何解决它？

    private class fetchdata extends AsyncTask<Void, Void, Void> {
            public Activity activity;      
            public fetchdata(Activity a)
            {
                activity = a;
            }  
            protected Void doInBackground(Void...voids)
            {
                String[] page = new String[16384]; //Number is just for testing, don't worry
                try {
                                page = executeHttpGet();
                        } catch (Exception e) {
                                page[0] = "Error";
                        }
                displayFetchedData(page);
                return null;
            }
    public String[] executeHttpGet() throws Exception {
         URL u;
        InputStream is = null;
        DataInputStream dis = null;
        String s;
        int i = 0;
        int hostselection;
        boolean skip;
        String[] page = new String[16384];
        String[] serverurls = new String[2];
        addSecurityException();
        SharedPreferences dataprefs = getSharedPreferences("serverdata", Context.MODE_PRIVATE);        
        hostselection = dataprefs.getInt("selectedhost", 0);
        SharedPreferences preferences;
        preferences = PreferenceManager.getDefaultSharedPreferences(activity);
        serverurls[0] = preferences.getString("server01", "");
        serverurls[1] = preferences.getString("server02", "");
        for (int j = 0; j < 2; j++)
        {
         skip = false;
         if (j == 0)
         {
                         if (hostselection == 0 || hostselection == 1)
                             {
                                 Authenticator.setDefault(new MyAuthenticator(activity, false));
                             }
                         else
                         {
                                 skip = true;
                         }
         }
         if (j == 1)
         {
                         if (hostselection == 0 || hostselection == 2)
                             {
                                 Authenticator.setDefault(new MyAuthenticator(activity, true));
                             }
                         else
                         {
                                 skip = true;
                         }
         }
         if (skip == false)
         {
                         try {
                            u = new URL(serverurls[j]);
                            is = u.openStream();        //LINE IN QUESTION
                            dis = new DataInputStream(new BufferedInputStream(is));
                            while ((s = dis.readLine()) != null)
                            {
                                if (s.length() > 18)
                                {
                                        page[i] = s;
                                        i++;
                                }
                            }
                         }
                         catch (IOException ioe)
                         {
                                 ioe.printStackTrace();
                         }
                         is.close();
                      }
        }
        return page;
   }

Answer 1

从您获得的输入流中创建一个BufferedInputStream，然后调用mark()以输入流长度作为参数的方法。下次需要重用流时调用reset()。