How can I return value from function onResponse of Volley?

Question

public class getString  { String tag_string_req = "string_raq"; String url = "http://10.0.2.2/eat/locations/index.json"; String result="";  public String get_String() {     StringRequest strReq = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {         @Override         public void onResponse(String response) {             result=response;             System.out.println(response);             ;          }     }, new Response.ErrorListener() {         @Override         public void onErrorResponse(VolleyError volleyError) {             System.out.println(volleyError.getMessage());         }     });     AppController.getInstance().addToRequestQueue(strReq, tag_string_req);     return result; }} 

I would to build an object of getString and call get_String in other fields. But it seems that it is hard to get the result out from the onResponse. I know it cannot work in this current way. Could anyone help me to settle this problem?

Answer 1

You want to use callback interfaces like so:

public void getString(final VolleyCallback callback) {     StringRequest strReq = new StringRequest(Request.Method.GET, url, new     Response.Listener<String>() {         @Override         public void onResponse(String response) {             ...  // (optionally) some manipulation of the response              callback.onSuccess(response);         }     }... }} 

Where the callback is defined as

public interface VolleyCallback{     void onSuccess(String result); } 

Example code inside activity:

public void onResume(){     super.onResume();      getString(new VolleyCallback(){          @Override          public void onSuccess(String result){              ... //do stuff here          }     }); } 

You can also make VolleyCallback more robust, using generic types if you want to do processing, or adding start(), failed(Exception e), complete(), etc methods to do a little more fine-grained state checking.

Keep in mind this is an async call, so you will have to update views, etc when you get the result back (inside success()).