Android: How handle message error from the server using Volley?

I’ve implemented something similar to this, and it’s relatively simple. Your log message is printing out what looks like gibberish, because response.data is really a byte array – not a String. Also, a VolleyError is really just an extended Exception, so Exception.getMessage() likely wouldn’t return what you are looking for unless you override the parsing methods for parsing your VolleyError in your extended Request class. A really basic way to handle this would be to do something like:

//In your extended request class
@Override
protected VolleyError parseNetworkError(VolleyError volleyError){
        if(volleyError.networkResponse != null && volleyError.networkResponse.data != null){
                VolleyError error = new VolleyError(new String(volleyError.networkResponse.data));
                volleyError = error;
            }

        return volleyError;
    }
}

If you add this to your extended Request classes, your getMessage() should at least not return null. I normally don’t really bother with this, though, since it’s easy enough to do it all from within your onErrorResponse(VolleyError e) method.

You should use a JSON library to simplify things — I use Gson for example or you could use Apache’s JSONObjects which shouldn’t require an additional external library. The first step is to get the response JSON sent from your server as a String (in a similar fashion to what I just demonstrated), next you can optionally convert it to a JSONObject (using either apache’s JSONObjects and JsonArrays, or another library of your choice) or just parse the String yourself. After that, you just have to display the Toast.

Here’s some example code to get you started:

public void onErrorResponse(VolleyError error) {
     String json = null;

     NetworkResponse response = error.networkResponse;
     if(response != null && response.data != null){
         switch(response.statusCode){
             case 400:
                  json = new String(response.data);
                  json = trimMessage(json, "message");
                  if(json != null) displayMessage(json);
                  break;
             }
            //Additional cases
     }
}

public String trimMessage(String json, String key){
    String trimmedString = null;

    try{
        JSONObject obj = new JSONObject(json);
        trimmedString = obj.getString(key);
    } catch(JSONException e){
        e.printStackTrace();
        return null;
    }

    return trimmedString;
}

//Somewhere that has access to a context
public void displayMessage(String toastString){
    Toast.makeText(context, toastString, Toast.LENGTH_LONG).show();
}