I’m developing an Android application that uses Retrofit to call a model hosted on Render. The endpoint is supposed to accept a request with a state and a year, and return a JSON object containing predicted rainfall data.

Here’s an example of a typical JSON response:

{
  "predicted_rainfall": {
    "APR": 124.20799999999997,
    "AUG": 358.282,
    "DEC": 68.95199999999994,
    "FEB": 27.997999999999966,
    "JAN": 18.76000000000003,
    "JUL": 911.7139999999999,
    "JUN": 666.5559999999996,
    "MAR": 44.099999999999994,
    "MAY": 177.19000000000023,
    "NOV": 259.6499999999997,
    "OCT": 305.5620000000003,
    "SEP": 296.3400000000001
  },
  "state": "KERALA",
  "year": "1901"
}

The endpoint is "https://rainfallpredictionmodel.onrender.com/predict/rainfall".

I created a Retrofit setup to call this endpoint, but it always fails with an error stating that it “failed to connect.” Initially, I used Volley but faced the same issue, prompting the switch to Retrofit.

Here’s the code for the Retrofit setup:

import retrofit2.Retrofit
import retrofit2.converter.gson.GsonConverterFactory
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response
import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import com.google.android.material.bottomsheet.BottomSheetDialogFragment
import okhttp3.OkHttpClient
import org.json.JSONObject
import java.util.concurrent.TimeUnit

class BottomSheetRainfall : BottomSheetDialogFragment() {
    private val TAG = "RainfallFragment"

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_bottom_sheet_rainfall, container, false)
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        val submitButton = view.findViewById<Button>(R.id.submit_rainfall)
        val stateNameEditText = view.findViewById<EditText>(R.id.state_name)
        val yearEditText = view.findViewById<EditText>(R.id.year)

        val okHttpClient = OkHttpClient.Builder()
            .connectTimeout(30, TimeUnit.SECONDS)  // Increased connection timeout
            .readTimeout(30, TimeUnit.SECONDS)     // Increased read timeout
            .writeTimeout(30, TimeUnit.SECONDS)    // Increased write timeout
            .build()

        val retrofit = Retrofit.Builder()
            .baseUrl("https://rainfallpredictionmodel.onrender.com/")
            .client(okHttpClient)
            .addConverterFactory(GsonConverterFactory.create())
            .build()

        val rainfallService = retrofit.create(RainfallService::class.java)

        submitButton.setOnClickListener {
            val state = stateNameEditText.text.toString().uppercase()
            val year = yearEditText.text.toString()

            if (state.isNotEmpty() && year isNotEmpty()) {
                val request = RainfallRequest(state, year)

                rainfallService.predictRainfall(request).enqueue(object : Callback<RainfallResponse> {
                    override fun onResponse(
                        call: Call<RainfallResponse>,
                        response: Response<RainfallResponse>
                    ) {
                        if (response.isSuccessful) {
                            val predictedRainfall = response.body()?.predicted_rainfall ?: emptyMap()
                            Toast.makeText(
                                requireContext(),
                                "Rainfall data retrieved successfully",
                                Toast.LENGTH_SHORT
                            ).show()
                        } else {
                            Toast.makeText(
                                requireContext(),
                                "Error: ${response.message()}",
                                Toast.LENGTH_SHORT
                            ).show()
                        }
                    }

                    override fun onFailure(call: Call<RainfallResponse>, t: Throwable) {
                        Log.e(TAG, "Error during API call", t)
                        Toast.makeText(requireContext(), "Error: ${t.localizedMessage}", Toast.LENGTH_SHORT).show()
                    }
                })
            } else {
                Toast.makeText(requireContext(), "Please enter both state and year", Toast.LENGTH_SHORT).show()
            }
        }
    }
}

The RainfallService interface looks like this:

package com.example.safenet

import retrofit2.Call
import retrofit2.http.Body
import retrofit2.http.POST

interface RainfallService {
    @POST("predict/rainfall")
    fun predictRainfall(@Body request: RainfallRequest): Call<RainfallResponse>
}

And here are the data classes for the request and response:

package com.example.safenet

data class RainfallRequest(val state: String, val year: String)

data class RainfallResponse(val predicted_rainfall: Map<String, Double>)

Despite this setup, I keep getting the following error: “Failed to connect to https://rainfallpredictionmodel.onrender.com/predict/rainfall.” The same error occurs with both Retrofit and Volley. I would appreciate any advice on resolving this issue.