How can I return a value from the onResponse of Retrofit function?

Question

I'm trying to return the value that I get from the onResponse method in a request to call retrofit , is there a way so that I can get this value from the override method? here is my code:

 public JSONArray RequestGR(LatLng start, LatLng end) { final JSONArray jsonArray_GR; EndpointInterface loginService = ServiceAuthGenerator.createService(EndpointInterface.class); Call<GR> call = loginService.getroutedriver(); call.enqueue(new Callback<GR>() { @Override public void onResponse(Response<GR> response , Retrofit retrofit) { jsonArray_GR = response.body().getRoutes(); //i need to return this jsonArray_GR in my RequestGR method } @Override public void onFailure(Throwable t) { } }); return jsonArray_GR; } 

I cannot get the value of jsonArray_GR , because in order to be able to use it in the onResponse method, I need to declare it final, and I cannot give it a value.

Answer 1

The problem is that you are trying to return an enqueue value enqueue , but it is an asynchronous method using a callback, so you cannot do this. You have 2 options:

• You can change your RequestGR method to accept a callback and then associate an enqueue callback with it. This is similar to mapping within frameworks such as rxJava.

It will look something like this:

 public void RequestGR(LatLng start, LatLng end, final Callback<JSONArray> arrayCallback) { EndpointInterface loginService = ServiceAuthGenerator.createService(EndpointInterface.class); Call<GR> call = loginService.getroutedriver(); call.enqueue(new Callback<GR>() { @Override public void onResponse(Response<GR> response , Retrofit retrofit) { JSONArray jsonArray_GR = response.body().getRoutes(); arrayCallback.onResponse(jsonArray_GR); } @Override public void onFailure(Throwable t) { // error handling? arrayCallback.onFailure(t)? } }); } 

The caveat with this approach is that it simply pushes asynchronous content to another level, which may be a problem for you.

2. You can use an object similar to BlockingQueue , Promise or Observable , or even your own container object (be careful to be thread safe), which allows you to check and set the value.

It will look like this:

 public BlockingQueue<JSONArray> RequestGR(LatLng start, LatLng end) { // You can create a final container object outside of your callback and then pass in your value to it from inside the callback. final BlockingQueue<JSONArray> blockingQueue = new ArrayBlockingQueue<>(1); EndpointInterface loginService = ServiceAuthGenerator.createService(EndpointInterface.class); Call<GR> call = loginService.getroutedriver(); call.enqueue(new Callback<GR>() { @Override public void onResponse(Response<GR> response , Retrofit retrofit) { JSONArray jsonArray_GR = response.body().getRoutes(); blockingQueue.add(jsonArray_GR); } @Override public void onFailure(Throwable t) { } }); return blockingQueue; } 

Then you can synchronously wait for the result in your calling method as follows:

 BlockingQueue<JSONArray> result = RequestGR(42,42); JSONArray value = result.take(); // this will block your thread 

I would highly recommend reading in a framework like rxJava, for example.