Unable to create call adapter for retrofit2.response<okhttp3.responsebody>

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Java

Android

Quote:

I am trying to send a POST request to google's FCM server , so that I can Subscribe to a particular Topic and send/Receive messages.

Below I have also used RxJava3 to set the Call Adapter for my Retrofit. I am new to these functions , I think I am missing something here. I am not sure should I change the return types for my API or Change the Call Adapters. Any Help is Appreciated.

EXCEPTION IN LOGCAT : Unable to create call adapter for retrofit2.Response<okhttp3.responsebody> for method NotificationAPI.postNotification

BUILD.GRADLE(APP)

    plugins {
    id 'com.android.application'
}
android {
    compileSdkVersion 30
    buildToolsVersion "30.0.2"
    defaultConfig {
        applicationId "com.deepesh.myfcmapp"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}
dependencies {
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    testImplementation 'junit:junit:4.13.1'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    implementation platform('com.google.firebase:firebase-bom:26.0.0')
    implementation 'com.google.firebase:firebase-messaging:21.0.0'

    // retrofit
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.9.0'

    implementation 'io.reactivex.rxjava3:rxandroid:3.0.0'
    implementation 'io.reactivex.rxjava3:rxjava:3.0.0'
    implementation 'com.squareup.retrofit2:adapter-rxjava3:2.9.0'
}
apply plugin: 'com.google.gms.google-services'

MainActivity.java

package com.deepesh.myfcmapp;

import androidx.appcompat.app.AppCompatActivity;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import com.google.firebase.messaging.FirebaseMessaging;
import com.google.gson.Gson;
import okhttp3.ResponseBody;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava3.RxJava3CallAdapterFactory;
import retrofit2.converter.gson.GsonConverterFactory;


public class MainActivity extends AppCompatActivity {

    public static final String FCM_CHANNEL_ID = "fcm_channel_id";
    private static final String TAG = "TAG";
    EditText title_editText, message_editText, token_editText;
    Button send_button;
    Retrofit retrofit1;
    NotificationAPI notificationAPI;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FirebaseMessaging.getInstance().subscribeToTopic(MyConstants.TOPIC);

        init();

        // CREATE NOTIFICATION CHANNEL
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel fcm_channel = new NotificationChannel(FCM_CHANNEL_ID, "FCM channel", NotificationManager.IMPORTANCE_HIGH);
            NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
            manager.createNotificationChannel(fcm_channel);
        }


    }


    void init() {
        title_editText = findViewById(R.id.title_editText);
        token_editText = findViewById(R.id.token_editText);
        message_editText = findViewById(R.id.message_editText);
        send_button = findViewById(R.id.send_button);
        send_button.setOnClickListener(clickListener);
    }


    void sendNotififcation(PushNotification pushnotification) {

        retrofit1 = new Retrofit.Builder()
                .addConverterFactory(GsonConverterFactory.create())
                .baseUrl(MyConstants.BASE_URL)

NotificationService.java

package com.deepesh.myfcmapp;

   import android.app.Notification;
   import android.app.NotificationManager;
   import android.app.PendingIntent;
   import android.content.Intent;
   import androidx.annotation.NonNull;
   import androidx.core.app.NotificationCompat;
   import com.google.firebase.messaging.FirebaseMessagingService;
   import com.google.firebase.messaging.RemoteMessage;
   import java.util.Random;

   public class NotificationService extends FirebaseMessagingService {


       @Override
       public void onMessageReceived(@NonNull RemoteMessage message) {
           super.onMessageReceived(message);

           Intent intent = new Intent(this,MainActivity.class);
           int NotififcationID = new Random().nextInt();
           PendingIntent pendingIntent = PendingIntent.getActivity(this,0 , intent,PendingIntent.FLAG_ONE_SHOT);
           NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);

           Notification notification = new NotificationCompat.Builder(this, MainActivity.FCM_CHANNEL_ID)
                   .setContentTitle(message.getData().get("title"))
                   .setContentText(message.getData().get("message"))
                   .setSmallIcon(R.drawable.ic_baseline_chat_24)
                   .setAutoCancel(true)
                   .setContentIntent(pendingIntent)
                   .build();
           manager.notify(NotififcationID,notification);

       }


       @Override
       public void onNewToken(@NonNull String s) {
           super.onNewToken(s);
       }

   }

NotificationData.java

package com.deepesh.myfcmapp;

public class NotififcationData {

    String title;
    String message;

    public NotififcationData(String title, String message) {
        this.title = title;
        this.message = message;
    }
    
}

PushNotification.java

package com.deepesh.myfcmapp;

public class PushNotification {

// variable names should be same as in the formats

    String to;
    NotififcationData data;

    public PushNotification(String to, NotififcationData data) {
        this.to = to;
        this.data = data;
    }
}

NotificationAPI.java

package com.deepesh.myfcmapp;

import okhttp3.ResponseBody;
import retrofit2.Response;
import retrofit2.http.Body;
import retrofit2.http.Headers;
import retrofit2.http.POST;

public interface NotificationAPI {


    @Headers({"Authorization: key="+ MyConstants.SERVER_KEY,"Content-Type:"+ MyConstants.CONTENT_TYPE} )
    @POST("fcm/send")
    Response<ResponseBody> postNotification(@Body PushNotification pushNotification);

}

What I have tried:

I tried importing some Call adapters like RXJAVA2 , 3 , but they still give the sa,e result.