Post a JSONArray with volley and retrieve a String

Question

I am pretty new to android developing and working with volley and got a few questions. I am trying to send a JSONArray via Post with volley and try to get back a String as response.

I have downloaded the volley files via github and got within the toolbox the JsonArrayRequest.java. This file contains a lot of information which I need for my task so I decided to mix it with the StringRequest.java and got out following:

New class called SendingJsonArray.java

package com.android.volley.toolbox;
import com.android.volley.NetworkResponse;
import com.android.volley.ParseError;
import com.android.volley.Response;
import com.android.volley.Response.ErrorListener;
import com.android.volley.Response.Listener;
import org.json.JSONArray;
import org.json.JSONException;
import java.io.UnsupportedEncodingException;
/**
 * A request for retrieving a {@link JSONArray} response body at a given URL.
 */
public class SendingJsonArray extends JsonRequest<JSONArray> {
 /**
 * Creates a new request.
 * @param url URL to fetch the JSON from
 * @param listener Listener to receive the JSON response
 * @param errorListener Error listener, or null to ignore errors.
 */
 public SendingJsonArray(String url, JSONArray JsonArry, Listener<JSONArray> listener, ErrorListener errorListener) {
 super(Method.POST, url, JsonArry, listener, errorListener);
 }
 @Override
 protected Response<JSONArray> parseNetworkResponse(NetworkResponse response) {
 try {
 String jsonString =
 new String(response.data, HttpHeaderParser.parseCharset(response.headers));
 return Response.success(new JSONArray(jsonString),
 HttpHeaderParser.parseCacheHeaders(response));
 } catch (UnsupportedEncodingException e) {
 return Response.error(new ParseError(e));
 } catch (JSONException je) {
 return Response.error(new ParseError(je));
 }
 }
}

1. The first strange thing is that SendingJsonArray() doesn't contain a int method? It compiles and seems to work without it.

2. Than I changed the Method.GET to Method.POST. It compiles and seems to work again.

3. Than I added the "JSONArray JsonArry" within the SendingJsonArray and get following error:

   error: no suitable constructor found for JsonRequest(int,String,JSONArray,Listener<JSONArray>,ErrorListener)
   [javac] super(Method.POST, url, JsonArry, listener, errorListener);
   [javac] ^
   [javac] constructor JsonRequest.JsonRequest(int,String,String,Listener<JSONArray>,ErrorListener) is not applicable
   [javac] (actual argument JSONArray cannot be converted to String by method invocation conversion)
   [javac] constructor JsonRequest.JsonRequest(String,String,Listener<JSONArray>,ErrorListener) is not applicable
   [javac] (actual and formal argument lists differ in length)
   [javac] 1 error
   

OK I know what the problem is but I don t know how to solve this. Where is the original constructor and how can I modify mine that this will work?

4. If I get this working there will be the response listener left. I would try to copy the listener of StringRequest.java and hope that this will work?

   @Override
   protected void deliverResponse(String response) {
    mListener.onResponse(response);
   }
   @Override
   protected Response<String> parseNetworkResponse(NetworkResponse response) {
    String parsed;
    try {
    parsed = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
    } catch (UnsupportedEncodingException e) {
    parsed = new String(response.data);
    }
    return Response.success(parsed, HttpHeaderParser.parseCacheHeaders(response));
   }
   

Why are there two and what exactly are they created for? Sorry but the documentation about that isn't really helpful for me :/

Thanks for your help! :)

• TommySM: this might help with GET : stackoverflow.com/questions/29761634/… and this might help with POST: stackoverflow.com/questions/29779447/…

Answer 1

In order to send a JSONArray as param with volley library I implemented this class called JSONPostArrayRequest, which extends JSONRequest, maybe it can help you:

public class JsonPostArrayRequest extends JsonRequest<JSONObject> {
 JSONArray params;
 public JsonPostArrayRequest(String url, Response.Listener<JSONObject> listener, Response.ErrorListener errorListener,JSONArray params) {
 super(Method.POST, url, null, listener, errorListener);
 this.params=params;
 }
 @Override
 public byte[] getBody() {
 if ( this.params != null && this.params.length() > 0) {
 return encodeParameters( this.params, getParamsEncoding());
 }
 return null;
 }
 private byte[] encodeParameters(JSONArray params, String paramsEncoding) {
 try {
 return params.toString().getBytes(paramsEncoding);
 } catch (UnsupportedEncodingException uee) {
 throw new RuntimeException("Encoding not supported: " + paramsEncoding, uee);
 }
 }
 @Override
 protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) {
 try {
 String jsonString =
 new String(response.data, HttpHeaderParser.parseCharset(response.headers));
 return Response.success(new JSONObject(jsonString),
 HttpHeaderParser.parseCacheHeaders(response));
 } catch (UnsupportedEncodingException e) {
 return Response.error(new ParseError(e));
 } catch (JSONException je) {
 return Response.error(new ParseError(je));
 }
 }
}