如何处理应用程序，如果服务器不可用

Question

在那里。我有一个基于远程服务器的应用程序。我的应用程序工作完美，如果服务器正在运行，并崩溃，如果服务器不可用。我测试应用程序在本地主机，所以我想处理它，我的异步任务代码如下。

public class UserBackgroundTask extends AsyncTask<String, Void, String> { 
    Context context; 
    public ProgressDialog progressDialog; 

    public UserBackgroundTask(Context context) { 
     this.context = context; 
    } 

    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     progressDialog = new ProgressDialog(MainActivity.this); 
     progressDialog.setMessage("Verifying Username and Password..."); 
     progressDialog.show(); 
    } 


    @Override 
    protected String doInBackground(String... params) { 

     String login_url = "http://10.0.3.2/newRsNepal/Login.php"; 
     HttpURLConnection httpURLConnection = null; 
     String method = params[0]; 

     if (method.equals("login")) { 
      String login_user = params[1]; 
      String login_password = params[2]; 

      try { 
       URL url = new URL(login_url); 
       httpURLConnection = (HttpURLConnection) url.openConnection(); 
       httpURLConnection.setRequestMethod("POST"); 
       httpURLConnection.setDoOutput(true); 
       httpURLConnection.setDoInput(true); 
       OutputStream outputStream = httpURLConnection.getOutputStream(); 
       BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8")); 
       String data = URLEncoder.encode("username", "UTF-8") + "=" + URLEncoder.encode(login_user, "UTF-8") + "&" + 
         URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode(login_password, "UTF-8"); 
       bufferedWriter.write(data); 
       bufferedWriter.flush(); 
       bufferedWriter.close(); 
       outputStream.close(); 
       InputStream inputStream = httpURLConnection.getInputStream(); 
       BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1")); 
       String response = ""; 
       String line = ""; 
       while ((line = bufferedReader.readLine()) != null) { 
        response += line; 
       } 
       bufferedReader.close(); 
       inputStream.close(); 
       httpURLConnection.disconnect(); 
       return response; 
      } catch (MalformedURLException e) { 
       e.printStackTrace(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
     } 
     return null; 
    } 

    @Override 
    protected void onPostExecute(String result) { 

     if (result.equalsIgnoreCase("1")) { 
      progressDialog.dismiss(); 
      Intent intent = new Intent(getApplicationContext(), InnerActivity.class); 
      intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); 
      intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); // Add new Flag to start new Activity 
      startActivity(intent); 
      finish(); 
     } else { 
      progressDialog.dismiss(); 
      Toast.makeText(context, "Invalid username and Password", Toast.LENGTH_LONG).show(); 
      textUser.setText(""); 
      textUser.setText(""); 
     } 
    } 

    @Override 
    protected void onProgressUpdate(Void... values) { 
     super.onProgressUpdate(values); 
    } 
} 

Answer 1

在PostExecute使用此代码：

if (result.length>1) { 
    Toast.makeText(YourActivity.this,"Your msg", Toast.LENGTH_SHORT).show(); 
} 

或

if (result.size>1) { 
    Toast.makeText(YourActivity.this,"Your msg", Toast.LENGTH_SHORT).show(); 
    } 

或

if (result==null) { 
    } 

Answer 2

把下面的代码在MainActivity文件

//this function check internet connection 
    private boolean isNetworkAvailable() { 
       ConnectivityManager connectivityManager 
         = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); 
       NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo(); 
       return activeNetworkInfo != null && activeNetworkInfo.isConnected(); 
      } 

//put your code here 
if(isNetworkAvailable() == true) 
{ 
     //internet connection available put your code here 
     new UserBackgroundTask().execute(); 
} 
else 
{ 
     //internet connection not available  
}