Question

我这里有一个将数据从远程服务器下载到文件的功能。我对我的代码仍然没有信心。我的问题是，如果在读取流并将数据保存到文件中并且突然我在互联网上断开连接时，下面的这些捕获异常会真的能够捕获到那种事件吗？如果没有，你能否建议如何处理这类事件？

注意：我在一个线程中调用此函数，以便不阻止UI。

public static boolean getFromRemote(String link, String fileName, Context context){ 
        boolean dataReceived = false;
        ConnectivityManager connec =  (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);

            if (connec.getNetworkInfo(0).isConnected() || connec.getNetworkInfo(1).isConnected()){
                try {
                        HttpClient httpClient = new DefaultHttpClient();
                        HttpGet httpGet = new HttpGet(link);
                        HttpParams params = httpClient.getParams();
                        HttpConnectionParams.setConnectionTimeout(params, 30000);
                        HttpConnectionParams.setSoTimeout(params, 30000);
                        HttpResponse response;
                        response = httpClient.execute(httpGet);
                        int statusCode = response.getStatusLine().getStatusCode();
                        if (statusCode == 200){
                            HttpEntity entity = response.getEntity();



                            InputStream in = null;
                            OutputStream output = null;

                            try{
                                in = entity.getContent();

                                String secondLevelCacheDir = context.getCacheDir() + fileName;

                                File imageFile = new File(secondLevelCacheDir);

                                output= new FileOutputStream(imageFile);
                                IOUtilities.copy(in, output);
                                output.flush();
                            } catch (IOException e) {
                                Log.e("SAVING", "Could not load xml", e);
                            } finally {
                                IOUtilities.closeStream(in);
                                IOUtilities.closeStream(output);
                                dataReceived = true;

                            }
                        }
                    }catch (SocketTimeoutException e){  
                        //Handle not connecting to client !!!!
                        Log.d("SocketTimeoutException Thrown", e.toString());
                        dataReceived = false;

                    } catch (ClientProtocolException e) {
                        //Handle not connecting to client !!!!
                        Log.d("ClientProtocolException Thrown", e.toString());
                        dataReceived = false;

                    }catch (MalformedURLException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                        dataReceived = false;
                        Log.d("MalformedURLException Thrown", e.toString());
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                        dataReceived = false;
                        Log.d("IOException Thrown", e.toString());
                    } 
                }
            return dataReceived;

        }

Answer 1

在开始网络通信之前，我使用以下代码段来检查网络是否可用（预防比治疗更好？）。一旦通信开始，我只能希望网络始终可用。如果没有，我会抛出异常抛出并向用户显示一条消息。

public boolean isNetworkAvailable() {
   Context context = getApplicationContext();
   ConnectivityManager connectivity = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
   if (connectivity == null) {
      boitealerte(this.getString(R.string.alert),"getSystemService rend null");
   } else {
      NetworkInfo[] info = connectivity.getAllNetworkInfo();
      if (info != null) {
         for (int i = 0; i < info.length; i++) {
            if (info[i].getState() == NetworkInfo.State.CONNECTED) {
               return true;
            }
         }
      }
   }
   return false;
}

如果在异常提升代码中未被捕获任何异常，您可以使用任何线程附加DefaultThreadHandler。

[编辑：添加示例代码]

//attaching a Handler with a thread using the static function
Thread.setDefaultUncaughtExceptionHandler(handler);

//creating a Handler
private Thread.UncaughtExceptionHandler handler=
        new Thread.UncaughtExceptionHandler() {
        public void uncaughtException(Thread thread, Throwable ex) {
            Log.e(TAG, "Uncaught exception", ex);
            showDialog(ex);
        }
    };

void showDialog(Throwable t) {
        AlertDialog.Builder builder=new AlertDialog.Builder(mContext);
            builder
                .setTitle("Exception")
                .setMessage(t.toString())
                .setPositiveButton("Okay", null)
                .show();
    }

Android：下载数据时处理意外的互联网断开连接

1 个答案: