Unable to access response data out of VolleyRequest, attempted callbacks - android-volley

Question

I have tried using callback similar to my fragments and other people suggestion on callbacks, However I've had no luck i could be doing the callbacks wrong. The Toast inside the onResponse method of JsonArrayRequest returns an array size of 2. But i get 0 on the toast outside of the request. consignment.class implements parcelable
public class BackgroundTask{
String json_url;
Gson gson;
Type listType;
ProgressDialog pDialog;
ArrayList<Consignment> arrayList = new ArrayList<>();
AppController appController;
ConsAdapter adapter;
Context context;
public BackgroundTask(Context context){
this.context = context;
listType = new TypeToken<List<Consignment>>(){}.getType();
appController = AppController.getInstance();
gson = new Gson();
}
public void getAllCons(final GetAllConsListener callBack) {
String tag_json_obj = "json_obj_req";
//showProgressDialog();
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET, json_url,null,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
callBack.onSuccess(response.toString());
//hideProgressDialog();
Toast.makeText(context, "Consignments:"+arrayList.size(), Toast.LENGTH_LONG).show();
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
//Toast.makeText(context, "Error...", Toast.LENGTH_SHORT).show();
error.printStackTrace();
//hideProgressDialog();
}
});
appController.addToRequestQueue(jsonArrayRequest);
}
Activity Class:
public class GetConsActivity extends AppCompatActivity {
RecyclerView recyclerView;
ConsAdapter adapter;
RecyclerView.LayoutManager layoutManager;
ArrayList<Consignment> arrayList;
TextView txtView;
BackgroundTask backgroundTask;
Type listType;
Gson gson;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_get_cons);
recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setHasFixedSize(true);
gson = new Gson();
listType = new TypeToken<ArrayList<Consignment>>(){}.getType();
BackgroundTask backgroundTask = new BackgroundTask(GetConsActivity.this);
backgroundTask.getAllCons(new GetAllConsListener() {
#Override
public void onSuccess(String response) {
ArrayList<Consignment> list = parseResponse(response);
updateUI(list);
//Toast.makeText(GetConsActivity.this, "Consignments:"+arrayList.size(), Toast.LENGTH_LONG).show();
Log.d("ONSUCCESS", "ARRAYSIZE: "+arrayList.size());
}
});
}
public ArrayList<Consignment> parseResponse(String response){
ArrayList<Consignment> list = new ArrayList<>();
try {
JSONArray jsonArray = new JSONArray(response);
Log.d("PARSE", "parseResponse: "+jsonArray.length());
JSONObject jsonObject = jsonArray.getJSONObject(0);
for (int i = 0; i<jsonArray.length();i++){
Consignment con = null;
Log.d("PARSE", "parseID: "+jsonObject.getInt("conid"));
con.setConid(jsonObject.getInt("conid"));
Log.d("PARSE", "conID: "+con.getConid());
con.setDescription(jsonObject.getString("description"));
list.add(con);
}
Log.d("PARSED", "parsedResponse: "+list.size());
} catch (JSONException e) {
e.printStackTrace();
}
//arrayList =gson.fromJson(response,new TypeToken<ArrayList<Consignment>>(){}.getType());
//updateUI(arrayList);
return list;
}
public void updateUI(ArrayList<Consignment> consignments){
this.arrayList = consignments;
Log.d("UPDATE", "parseResponse: "+consignments.size());
if (adapter == null) {
adapter = new ConsAdapter(consignments,GetConsActivity.this);
recyclerView.setAdapter(adapter);
}else{
adapter.setConsignments(consignments);
adapter.notifyDataSetChanged();
}
}
Error:
D/mali_winsys: EGLint new_window_surface(egl_winsys_display*, void*, EGLSurface, EGLConfig, egl_winsys_surface**, egl_color_buffer_format*, EGLBoolean) returns 0x3000, [1440x2560]-format:1
E/RecyclerView: No adapter attached; skipping layout
I/qtaguid: Untagging socket 51
D/ViewRootImpl: MSG_RESIZED_REPORT: ci=Rect(0, 84 - 0, 0) vi=Rect(0, 84 - 0, 0) or=1
E/RecyclerView: No adapter attached; skipping layout
D/PARSE: parseResponse: 4
D/PARSE: parseID: 123456789
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.angel.createcon, PID: 26952
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.angel.createcon.Consignment.setConid(int)' on a null object reference
at com.angel.createcon.GetConsActivity.parseResponse(GetConsActivity.java:80)
at com.angel.createcon.GetConsActivity$2.onSuccess(GetConsActivity.java:56)
at com.angel.createcon.BackgroundTask$2.onResponse(BackgroundTask.java:50)
at com.angel.createcon.BackgroundTask$2.onResponse(BackgroundTask.java:47)
at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65)
at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:7331)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
I/Process: Sending signal. PID: 26952 SIG: 9
Application terminated.

Answer 1

So I'll take a stab at this - having the activity implement the listener that way is a bit strange, though I don't think that's the issue. I also don't understand why you chose to save the list type to a variable - I've not seen anyone do that before.
However, getting to your question about the toast and why it's 0 - If you're talking about the toast that comes after the getAllCons call -it's because that code is executed before the callback code. completes.
Try something like this and see what it does.
public class BackgroundTask{
String json_url;
Gson gson;
Type listType;
Context context;
public BackgroundTask(Context context){
this.context = context;
listType = new TypeToken<List<Consignment>>(){}.getType();
appController = AppController.getInstance();
gson = new Gson();
}
public void getAllCons(final GetAllConsListener callBack) {
String tag_json_obj = "json_obj_req";
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET, json_url,null,
new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
callBack.onSuccess(response.toString());
Toast.makeText(context, "Consignments:"+arrayList.size(), Toast.LENGTH_LONG).show();
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
error.printStackTrace();
}
});
appController.addToRequestQueue(jsonArrayRequest);
}
public class GetConsActivity extends AppCompatActivity {
RecyclerView recyclerView;
ConsAdapter adapter;
RecyclerView.LayoutManager layoutManager;
TextView txtView;
BackgroundTask backgroundTask;
Gson gson;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_get_cons);
recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setHasFixedSize(true);
gson = new Gson();
BackgroundTask backgroundTask = new BackgroundTask(GetConsActivity.this);
backgroundTask.getAllCons(new GetAllConsListener() {
#Override
public void onSuccess(String response) {
List<Consignment> values = parseResponse(response);
updateUI(values);
}
});
//code may execute here but callback is not yet complete.
}
public List<Consignment> parseResponse(String response){
return gson.fromJson(response,listType);
}
private void updateUI(List<Consignment> consignments){
if(adapter == null){
adapter = new ConsAdapter(consignments)
recyclerView.setAdapter(adapter);
} else {
adapter.consignments = consignments;
adapter.notifyDataSetChanged();
}
}