How do I catch error when access server

Question

I create my util to request data from the server :

public class PushServer {
      public static ArrayList<DataBean> getAllData() {
        ArrayList<DataBean> data = new ArrayList<DataBean>();

        String uriJson = "http://api.mydomain.com/news.html";
        String resp = Utils.getResponseText1(uriJson);

        try {
            JSONObject json = new JSONObject(resp);
            JSONArray jArray = json.getJSONArray("items");

            for (int i=0; i<jArray.length(); i++) {
                JSONObject jData = jArray.getJSONObject(i);

                DataBean bean = new DataBean();             
                bean.setMenu_ID(jData.getString("ID"));
                bean.setIsDisplay(jData.getString("First_Data"));
                bean.setCategoryName(jData.getString("Second_Data"));

                data.add(bean);
            }
        }
        catch(Exception e) {
            e.printStackTrace();
        }
        return data;
    }
 }

When i call my util in AsyncTask :

protected void onPreExecute() {
    super.onPreExecute();
    pgBar.setVisibility(View.VISIBLE);
}

protected Void doInBackground(Void... params) {
    try {
        databean = PushServer.getAllData();
    } catch (Exception e) {
        netError.setVisibility(View.VISIBLE);
    }
    return null;
}

I don't get an error response. My screen is blank when my connection is down... How do I make a response if the URL API can not be accessed by my android application, such as the Troubled connection, etc.

@MT8 I use ProgressBar pgBar.setVisibility(View.VISIBLE) in `onPreExecute` — Bertho Joris, Nov 12 '13 at 18:01
If you want to catch exceptions when calling your function, don't swallow all exceptions. — SLaks, Nov 12 '13 at 18:02
does it shows? i think when progress bar is shown then black screen doesnt appers — KOTIOS, Nov 12 '13 at 18:02
@MT8 My ProgressBar is show...But then disappeared as I put `pgBar.setVisibility(View.GONE)` in `onPostExecute` — Bertho Joris, Nov 12 '13 at 18:05
Alright thats fine , so it indicates that doInbackground task is completed — KOTIOS, Nov 12 '13 at 18:06
@SLaks I want my code `netError.setVisibility(View.VISIBLE)` show..I have made a design for this case — Bertho Joris, Nov 12 '13 at 18:06
@BerthoJoris: You need to understand what the inner `catch` block is doing and why you don't want it. — SLaks, Nov 12 '13 at 18:09
@SLaks I have tried removing the `try catch` block. But when the application tries to read the data and then the app turns problematic connection myapp directly experienced the force close. That's why I use `try catch`. How the best way? — Bertho Joris, Nov 12 '13 at 18:14

score 2 · Accepted Answer · edited May 23 '17 at 12:19

There are a few issues in your code. Most are not that important, but conceptually, there is a big one : you should not use an asynctask to access the network on android.

The flaws of AsyncTasks are explained in this thread.

Moreover, when it comes to your problem of catching an exception the right way, AsyncTasks are even worse : there is no error handling built-in. You could still have some kind of manual error handling implemented (retain the exception, and make it accessible via a getter, then ask if any exception was received when your asynctasks is done).

But more and more libs offer much more interesting alternatives when it comes to the network, and most of them propose a nice error handling model for async exceptions. Have a look at the thread I mentionned, RoboSpice is among the alternatives. And if you don't like it, it also lists all other well known alternatives at the end of the readme on github.

Interesting explanation... I will look and try this library – Bertho Joris Nov 12 '13 at 18:21 — Bertho Joris, Nov 12 '13 at 18:21

score 1 · Answer 2 · edited Nov 13 '13 at 16:42

You can use the droidQuery library to simplify this and provide error handling:

final ArrayList<DataBean> data = new ArrayList<DataBean>();
$.ajax(new AjaxOptions().url("http://api.mydomain.com/news.html").success(new Function() {
    @Override
    public void invoke($ d, Object... args) {
        JSONObject json = (JSONObject) args[0];
         JSONArray jArray = json.getJSONArray("items");
         for (int i=0; i<jArray.length(); i++) {
             JSONObject jData = jArray.getJSONObject(i);
              DataBean bean = new DataBean();             
              bean.setMenu_ID(jData.getString("ID"));
              bean.setIsDisplay(jData.getString("First_Data"));
              bean.setCategoryName(jData.getString("Second_Data"));
              data.add(bean);

              //hear you may want to make a call to handle the "next step" for how to process this bean.
         }
     }
}).error(new Function() {
    @Override
    public void invoke($ d, Object... args) {
        AjaxError error = (AjaxError) args[0];
        //print the error status code and reason to logcat
        Log.e("Ajax", "Error " + error.status + ": " + error.reason);
    }
}));

How do I catch error when access server

2 Answers2