I am integrating paytm all in one sdk in android and i am getting a success code everytime but the body is null in android

This is the code for APIInterface:

@Multipart
    @POST("paytm")
    @Headers({"Content-Type: application/json;charset=UTF-8"})
    Call<Token_Res> generateTokenCall(
            @HeaderMap Map<String, String> header,
            @Part("code") RequestBody language,
            @Part ("MID") RequestBody mid,
            @Part("ORDER_ID") RequestBody order_id,
            @Part("AMOUNT") RequestBody amount
    );

This is my Retrofit class:

package com.csk.jagdishshop.paytm;

import com.csk.jagdishshop.BuildConfig;
import com.csk.jagdishshop.NullOnEmptyConverterFactory;
import com.csk.jagdishshop.retrofit.APIService;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import java.util.Map;
import java.util.concurrent.TimeUnit;

import okhttp3.Interceptor;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.RequestBody;
import okhttp3.logging.HttpLoggingInterceptor;
import retrofit2.Call;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class ServiceWrapper {
    private APIService mServiceInterface;

    public ServiceWrapper(Interceptor mInterceptorheader) {
        mServiceInterface = getRetrofit(mInterceptorheader).create(APIService.class);
    }

    public Retrofit getRetrofit(Interceptor mInterceptorheader) {
        HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
        loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
        OkHttpClient mOkHttpClient = null;
        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        builder.connectTimeout(1201, TimeUnit.SECONDS);
        builder.readTimeout(901, TimeUnit.SECONDS);

        if (BuildConfig.DEBUG) {
//            HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
            loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
            builder.addInterceptor(loggingInterceptor);
        }

        mOkHttpClient = builder.build();
        Gson gson = new GsonBuilder().setLenient().create();
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://jagdishshop.com/api/")
                .addConverterFactory(new NullOnEmptyConverterFactory())
                .addConverterFactory(GsonConverterFactory.create(gson))
                .client(mOkHttpClient)
                .build();
        return retrofit;
    }

    public Call<Token_Res> getTokenCall(Map<String, String> header, String code, String mid, String order_id, String amount) {
        return mServiceInterface.generateTokenCall(
                header,convertPlainString(code), convertPlainString(mid), convertPlainString(order_id)
                , convertPlainString(amount)
                );
    }
    // convert aa param into plain text
    public RequestBody convertPlainString(String data){
        RequestBody plainString = RequestBody.create(data,MediaType.parse("text/plain"));
        return  plainString;
    }
}

This is the network calling activity:
getToken() method is used to generate token from paytm server. For that i used the init_transaction.php file and PaytmCehcsum.php file on my own server and requesting to that. header is for the Authorization:token to validate the user.

private  void getToken(){
        Map<String, String> header = new HashMap<>();
        header.put("Authorization",token);
        header.put("X-Requested-With","XMLHttpRequest");

        Log.e(TAG, " get token start");
        progressBar.setVisibility(View.VISIBLE);
        ServiceWrapper serviceWrapper = new ServiceWrapper(null);
        Call<Token_Res> call = serviceWrapper.getTokenCall(header,"12345", midString, orderIdString, txnAmountString);
        call.enqueue(new Callback<Token_Res>() {
            @Override
            public void onResponse(Call<Token_Res> call, Response<Token_Res> response) {
                Log.e(TAG, " respo "+ response.isSuccessful());
                Log.e(TAG,"response :"+response.body());
                progressBar.setVisibility(View.GONE);
                try {

                    if (response.isSuccessful() && response.body()!=null){
                        if (response.body().getBody().getTxnToken()!="") {
                            Log.e(TAG, " transaction token : "+response.body().getBody().getTxnToken());
                            startPaytmPayment(response.body().getBody().getTxnToken());
                        }else {
                            Log.e(TAG, " Token status false");
                        }
                    }
                }catch (Exception e){
                    Log.e(TAG, " error in Token Res "+e.toString());
                }
            }

            @Override
            public void onFailure(Call<Token_Res> call, Throwable t) {
                progressBar.setVisibility(View.GONE);
                Log.e(TAG, " response error "+t.toString());
            }
        });

    }

    public void startPaytmPayment (String token){

        txnTokenString = token;
        
        String host = "https://securegw.paytm.in/";
        String orderDetails = "MID: " + midString + ", OrderId: " + orderIdString + ", TxnToken: " + txnTokenString
                + ", Amount: " + txnAmountString;
        //Log.e(TAG, "order details "+ orderDetails);

        String callBackUrl = host + "theia/paytmCallback?ORDER_ID="+orderIdString;
        Log.e(TAG, " callback URL "+callBackUrl);
        PaytmOrder paytmOrder = new PaytmOrder(orderIdString, midString, txnTokenString, txnAmountString, callBackUrl);
        TransactionManager transactionManager = new TransactionManager(paytmOrder, new PaytmPaymentTransactionCallback(){
            @Override
            public void onTransactionResponse(Bundle bundle) {
                Log.e(TAG, "Response (onTransactionResponse) : "+bundle.toString());
            }

            @Override
            public void networkNotAvailable() {
                Log.e(TAG, "network not available ");
            }

            @Override
            public void onErrorProceed(String s) {
                Log.e(TAG, " onErrorProcess "+s.toString());
            }

            @Override
            public void clientAuthenticationFailed(String s) {
                Log.e(TAG, "Clientauth "+s);
            }

            @Override
            public void someUIErrorOccurred(String s) {
                Log.e(TAG, " UI error "+s);
            }

            @Override
            public void onErrorLoadingWebPage(int i, String s, String s1) {
                Log.e(TAG, " error loading web "+s+"--"+s1);
            }

            @Override
            public void onBackPressedCancelTransaction() {
                Log.e(TAG, "backPress ");
            }

            @Override
            public void onTransactionCancel(String s, Bundle bundle) {
                Log.e(TAG, " transaction cancel "+s);
            }
        });

        transactionManager.setShowPaymentUrl(host + "theia/api/v1/showPaymentPage");
        transactionManager.startTransaction(this, ActivityRequestCode);

    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        Log.e(TAG ," result code "+resultCode);
        
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == ActivityRequestCode && data != null) {
            Bundle bundle = data.getExtras();
            if (bundle != null) {
                for (String key : bundle.keySet()) {
                    Log.e(TAG, key + " : " + (bundle.get(key) != null ? bundle.get(key) : "NULL"));
                }
            }
            Log.e(TAG, " data "+  data.getStringExtra("nativeSdkForMerchantMessage"));
            Log.e(TAG, " data response - "+data.getStringExtra("response"));

            Toast.makeText(getApplicationContext(), data.getStringExtra("nativeSdkForMerchantMessage")
                    + data.getStringExtra("response"), Toast.LENGTH_SHORT).show();
        }else{
            Log.e(TAG, " payment failed");
        }
    }

Here everytime I am getting response = true & responseBody = null

This is the Logcat output:

D/OkHttp: --> POST https://jagdishshop.com/api/paytm http/1.1
D/OkHttp: Content-Type: application/json;charset=UTF-8
D/OkHttp: Content-Length: 816
D/OkHttp: Authorization: Bearer ...
D/OkHttp: X-Requested-With: XMLHttpRequest
D/OkHttp: --a67ac3f9-93a3-4a87-bdf5-85b447044dda
D/OkHttp: Content-Disposition: form-data; name="code"
D/OkHttp: Content-Transfer-Encoding: binary
D/OkHttp: Content-Type: text/plain; charset=utf-8
D/OkHttp: Content-Length: 5
D/OkHttp: 12345
D/OkHttp: --a67ac3f9-93a3-4a87-bdf5-85b447044dda
D/OkHttp: Content-Disposition: form-data; name="MID"
D/OkHttp: Content-Transfer-Encoding: binary
D/OkHttp: Content-Type: text/plain; charset=utf-8
D/OkHttp: Content-Length: 20
D/OkHttp: QKBnVxxxxxxxxx65
D/OkHttp: --a67ac3f9-93a3-4a87-bdf5-85b447044dda
D/OkHttp: Content-Disposition: form-data; name="ORDER_ID"
D/OkHttp: Content-Transfer-Encoding: binary
D/OkHttp: Content-Type: text/plain; charset=utf-8
D/OkHttp: Content-Length: 4
D/OkHttp: 8361
D/OkHttp: --a67ac3f9-93a3-4a87-bdf5-85b447044dda
D/OkHttp: Content-Disposition: form-data; name="AMOUNT"
D/OkHttp: Content-Transfer-Encoding: binary
D/OkHttp: Content-Type: text/plain; charset=utf-8
D/OkHttp: Content-Length: 3
D/OkHttp: 100
D/OkHttp: --a67ac3f9-93a3-4a87-bdf5-85b447044dda--
D/OkHttp: --> END POST (816-byte body)

D/OkHttp: <-- 200 OK https://jagdishshop.com/api/paytm (329ms)
D/OkHttp: Date: Tue, 15 Sep 2020 05:53:09 GMT
D/OkHttp: Server: Apache
D/OkHttp: Cache-Control: no-cache, private
D/OkHttp: X-RateLimit-Limit: 60
D/OkHttp: X-RateLimit-Remaining: 58
D/OkHttp: Vary: Authorization,User-Agent
D/OkHttp: Content-Length: 0
D/OkHttp: Keep-Alive: timeout=5, max=100
D/OkHttp: Connection: Keep-Alive
D/OkHttp: Content-Type: text/html; charset=UTF-8
D/OkHttp: <-- END HTTP (0-byte body)

The problem might be, that you POST to https://jagdishshop.com/api/paytm instead of PayTM.
Unless you'd fix your server-side implementation, it is extremely pointless trying to fix the client.

Please use below callback URL in Initiate transaction API (Server-side implementation).

Staging: https://securegw-stage.paytm.in/theia/paytmCallback?ORDER_ID=<ORDER_ID_HERE>
Production: https://securegw.paytm.in/theia/paytmCallback?ORDER_ID=<ORDER_ID_HERE>