Develop Reference

Nested volley request with Singleton class returns null

I am getting a error in my code. The outer request returns a data but the inner loop returns null.
What I am doing here is: I am requesting some data and again using the id that I get from the first request, i use it to send another request. Although I am receiving the first response, I am getting ERRORNull message in the second nested request.
I am sure that the url is correct. I have not been able to find the solution to this problem.
private ArrayList<Item> fetchApiData(){
String url="http://www.gadgetsinnepal.com.np/wp-json/wp/v2/posts/";
JsonArrayRequest jsArrayRequest = new JsonArrayRequest
(Request.Method.GET, url, null, new Response.Listener<JSONArray>() {
#Override
public void onResponse(JSONArray response) {
try {
// Parsing json array response
// loop through each json object
for (int i = 0; i < response.length(); i++) {
JSONObject item = (JSONObject) response
.get(i);
String id = item.getString("id");
String date = item.getString("date");
JSONObject titleobj = item
.getJSONObject("title");
String title= titleobj.getString("rendered");
String featuredMedia= item.getString("featured_media");
Toast.makeText(getApplicationContext(), "ID :" + id +" Date: "+ date+ " Title "+ title + featuredMedia,
Toast.LENGTH_SHORT).show();
JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
"http://www.gadgetsinnepal.com/wp-json/wp/v2/media/"+featuredMedia, null, new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject nested_response) {
try {
// Parsing json object response
// response will be a json object
JSONObject guilld = nested_response.getJSONObject("guid");
String featured_img_url = guilld.getString("rendered");
String nestid=nested_response.getString("id");
Toast.makeText(getApplicationContext(),nested_response.toString()+"IMAGE" + nestid,Toast.LENGTH_LONG).show();
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getApplicationContext(),
"ERROR"+error.getMessage(), Toast.LENGTH_LONG).show();
}
});
MySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsonObjReq);
}
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
// TODO Auto-generated method stub
}
});
MySingleton.getInstance(this).addToRequestQueue(jsArrayRequest);
}

This problem was solved by carefully examining where the error log was giving.
Having unique logs in your methods will make finding the place where the problem occurs easier to find.
In this case we found that something was happening in:
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getApplicationContext(),
"ERROR"+error.getMessage(), Toast.LENGTH_LONG).show();
}
Further investigation showed we got a response code 503 message there.
Reasons for this to happen: lifewire.com/503-service-unavailable-explained-2622940
Increasing the time out of the request seems to prevent this from occurring again.

How to return string in java methods?

I have a problem where i am unable to return a string from this method. I was unsuccessful when I tried creating a new variable outside the Response.Listener. This is probably very simple but how do I go about returning a string from this method. The string I want to return is the 'featured_img_url' string.
public String secondServiceCall(String featuredmedia){
JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
"http://www.gadgetsinnepal.com/wp-json/wp/v2/media/"+featuredmedia, null, new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject nested_response) {
try {
JSONObject guilld = nested_response.getJSONObject("guid");
String featured_img_url = guilld.getString("rendered");
Toast.makeText(getApplicationContext(),"IMAGE :" + featured_img_url,Toast.LENGTH_LONG).show();
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getApplicationContext(),
"ERROR "+error.getMessage(), Toast.LENGTH_LONG).show();
}
});
MySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsonObjReq);
return featured_img_url;
}

update your code to:
String featured_img_url = null;
public String secondServiceCall(String featuredmedia){
JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
"http://www.gadgetsinnepal.com/wp-json/wp/v2/media/"+featuredmedia, null, new Response.Listener<JSONObject>() {
#Override
public void onResponse(JSONObject nested_response) {
try {
JSONObject guilld = nested_response.getJSONObject("guid");
featured_img_url = guilld.getString("rendered");
Toast.makeText(getApplicationContext(),"IMAGE :" + featured_img_url,Toast.LENGTH_LONG).show();
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error: " + e.getMessage(),
Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getApplicationContext(),
"ERROR "+error.getMessage(), Toast.LENGTH_LONG).show();
}
});
MySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsonObjReq);
return featured_img_url;
}

Here, you should simply pass the instance that call this methods to execute the methods from the response.
So change the methods to :
public void secondServiceCall(String featuredmedia, final MyClass caller){
Note that this will return nothing. And the caller instance need to be final to be used in the inner class JsonObjectRequest.
and in the response, you need to pass the value to the instance of MyClass. So add a method in MyClass
public void setFeatureImgUrl(String featuredImgUrl){ ... }
and you just need to call this in the response.
public void onResponse(JSONObject nested_response) {
...
caller.setFeatureImgUrl(feature_img_url);
...
}
Note : This could be done with an Observer pattern but I know that some people doesn't like it. I could add an example of it if needed.

Volley:Cannot refer to the non-final local variable in android

I have a following method, which submits http request using Volley:
private boolean SaveInformationToServer(Information information)
{
RequestQueue queue = Volley.newRequestQueue(this);
StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
try{
return true;
}
catch (Exception ex){
return false;
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
return false;
}
});
queue.add(stringRequest);
}
I require this method to return either true or false but currently it's giving error void method cannot return a value. I tried a variable, then I got cannot refer to the non-final local variable inside an inner class.
How can I make this method return a boolean value to its caller?

The return type of onResponse is void plus it's a function of an anonymous class so you can't return value from anonymous class to your caller of volley request.
You can create your function can call them on volley response and put your code to execute the result instead of keeping a flag, this will keep your code more structural and readable(you can also set you flags in your onSuccess).
void onSuccess(String response){
// do what you want to do
}
void onError(VolleyError error){
// do what you want to do
}
private void SaveInformationToServer(Information information)
{
RequestQueue queue = Volley.newRequestQueue(this);
StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
onSuccess(response);
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
onError(error);
}
});
queue.add(stringRequest);
}

Android, Volley Request, the response is blocking main thread

Something bad is happening when using Volley to treat a large response:
String url = AppHelper.DOMAIN + "/service/pages/profile_update.json";
this.infoTextView.setText(getString(R.string.profile_info_updating));
final StringRequest stringRequest = new StringRequest(Request.Method.POST, url,
new Response.Listener<String>() {
#Override
public void onResponse(String response) {
try {
JSONObject json = new JSONObject(response);
if (json.getBoolean("success")) {
// manage JSON object here
} else {
Toast.makeText(ProfileActivity.this,
getString(R.string.connection_problem_server),
Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
ProfileActivity.this.infoTextView.setText(
getString(R.string.profile_info_updating_error));
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
#Override
public void onErrorResponse(VolleyError error) {
ProfileActivity.this.infoTextView.setText(
getString(R.string.profile_info_updating_error));
if (error.networkResponse != null && error.networkResponse.statusCode == 401) {
Toast.makeText(ProfileActivity.this,
getString(R.string.connection_problem_permission),
Toast.LENGTH_LONG).show();
}
new android.os.Handler().postDelayed(new Runnable() {
#Override
public void run() {
if (ProfileActivity.this.swipeRefreshLayout != null) {
ProfileActivity.this.swipeRefreshLayout.setRefreshing(false);
}
}
}, 1000);
error.printStackTrace();
}
}) {
#Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<>();
params.put("auth_token", ProfileActivity.this.defaultUser.getAuthenticationToken());
return params;
}
#Override
public Map<String, String> getHeaders() throws AuthFailureError {
Map<String, String> params = new HashMap<>();
params.putAll(super.getHeaders());
params.put("Accept-Encoding", "gzip,deflate");
return params;
}
#Override
protected Response<String> parseNetworkResponse(NetworkResponse response) {
StringBuilder output = new StringBuilder();
try {
GZIPInputStream gStream = new GZIPInputStream(new ByteArrayInputStream(response.data));
InputStreamReader reader = new InputStreamReader(gStream);
BufferedReader in = new BufferedReader(reader, 16384);
String read;
while ((read = in.readLine()) != null) {
output.append(read).append("\n");
}
reader.close();
in.close();
gStream.close();
} catch (IOException error) {
error.printStackTrace();
return Response.error(new ParseError());
}
return Response.success(output.toString(), HttpHeaderParser.parseCacheHeaders(response));
}
};
stringRequest.setRetryPolicy(new RetryPolicy() {
#Override
public int getCurrentTimeout() {
// 40 seconds
return 40000;
}
#Override
public int getCurrentRetryCount() {
return DefaultRetryPolicy.DEFAULT_MAX_RETRIES;
}
#Override
public void retry(VolleyError error) throws VolleyError {
throw error;
}
});
Volley.newRequestQueue(this).add(stringRequest);
this code block the main thread, freezing the application.
Additionally, I set some header values to allow gzip response and a code to handle the data. But it is not the piece that make the undesired behavior. The application freeze only when onResponse(String response) starts.
What can I do to avoid this?

onResponse and onErrorResponse is called on UI thread hence any heavy operation done inside these methods will make you application less responsive. I guess you are trying to parse the response in onResponse() which is incorrect.
You have to move to parsing logic to parseNetworkResponse since this
is the method which is called in background thread. Refer the below link for more details :
https://developer.android.com/training/volley/request-custom.html

If it help someone , try to create a new thread in a method inside onResponse , inside that thread execute your parsing data. I hope the answer works for you

Sending POST Request and Receive Json Responds using Retrofit Unable to use Responds data I need to pass it to another activity

I am using Retrofit for sending POST request.Server return's a JSON Response and i am able to parse the response in the callback method. I need to pass the data from server to another activity. But i can't use the response data outside.
api.LoginUser(
Email.getText().toString(), // passing value to interface of retrofit
Password.getText().toString(),
new Callback<Response>() {
#Override
public void success(Response result, Response response) {
BufferedReader reader = null;
String output = "";
try {
reader = new BufferedReader(new InputStreamReader(result.getBody().in()));
output = reader.readLine();
} catch (IOException e) {
e.printStackTrace();
}
//Json PArsing
try {
JSONObject mainObject = new JSONObject(output);
JSONObject dataObj = mainObject.getJSONObject("data");
String id = dataObj.getString("id");
String name = dataObj.getString("name");
n=name;
Log.d("jsontext", n); //This works
}
catch(JSONException e)
{
e.printStackTrace();
}
Toast.makeText(MainActivity.this, output, Toast.LENGTH_LONG).show();
}
#Override
public void failure(RetrofitError error) {
//If any error occured displaying the error as toast
Toast.makeText(MainActivity.this, error.toString(), Toast.LENGTH_LONG).show();
}
}
);
I can't use this when it executes App crashes.its ok now there is no value in the variable.how to get values out of the callback Responds OnSuccess method???
Log.d("outer",n);
Intent dash = new Intent(this,Dashboard.class);
dash.putExtra("Value",fi);
startActivity(dash);
}

You can create an object and implement Serializable:
class User implements Serializable {
...
}
Then put object User to bundle, add to intent:
Bundle bundle = new Bundle();
bundle.putSerializable("data", user);
Intent intent = new Intent(this, YourClass.class);
intent.putExtras(bundle);
startActivity(intent);
Hope it help you.

Hold all data in a string and using intent app another activity and parse it;

You can do it as follows
public void onSuccess(int statusCode, Header[] headers,
byte[] response) {
try {
BufferedReader br = new BufferedReader(
new InputStreamReader(new ByteArrayInputStream(
response)));
String st = "";
String st1 = "";
while ((st = br.readLine()) != null) {
st1 = st1 + st;
}
showStoreData(st1);
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void onFailure(int statusCode, Header[] headers,
byte[] errorResponse, Throwable e) {
// called when response HTTP status is "4XX" (eg. 401, 403, 404)
Log.e("FAIL", "FAIl" + statusCode);
}
#Override
public void onRetry(int retryNo) {
// called when request is retried
}
});
after that
public void showStoreData(String st) {
Intent intent = new Intent(this, YourClass.class);
intent.putExtras(st);
startActivity(intent);
}

You should use an interface that you initialize from the calling method and pass as a parameter into you request class, that way you can call the requests from anywhere and get the callback response back to where you called it from, an example would be:
A general interface, separated in another file:
public interface SomeCustomListener<T>
{
public void getResult(T object);
}
In the class holding your call (complete the stuff you need):
public void someRequestReturningString(Object param1, final SomeCustomListener<String> listener)
{
//here you initialize what you need... it's your stuff
response.enqueue(new Callback<ResponseBody>()
{
#Override
public void onResponse(Call<ResponseBody> call, retrofit2.Response<ResponseBody> rawResponse)
{
try
{
String response = rawResponse.body().string();
// do what you want with it and based on that...
//return it to who called this method
listener.getResult("someResultString");
}
catch (Exception e)
{
e.printStackTrace();
listener.getResult("Error1...");
}
}
#Override
public void onFailure(Call<ResponseBody> call, Throwable throwable)
{
try
{
// do something else in case of an error
listener.getResult("Error2...");
}
catch (Exception e)
{
throwable.printStackTrace();
listener.getResult("Error3...");
}
}
});
}
Then from where you're calling the request (could be anywhere, Fragments, onClicks, etc):
public class BlaBla
{
//.....
public void someMethod()
{
NetworkManager.getInstance().someRequestReturningString(someObject, new SomeCustomListener<String>()
{
#Override
public void getResult(String result)
{
if (!result.isEmpty())
{
//do what you need with the result...
}
}
});
}
}
If you need more context, you can refer to this SO thread.
Hope this helps!