[SOLVED] Exception: Cannot convert string type to JSON object

package uk.co.jonniegrieve.stormy;

import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.IOException;

import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends Activity {

    private static CurrentWeather mCurrentWeather;

    public static final String TAG = MainActivity.class.getSimpleName();

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //set up string to query API
        String apiKey = "c967557031449620255ff3c64b443a26";
        double latitude = 37.8267;
        double longitude = -122.4233;

        String forecastURL = "https://api.darksky.net/forecast/" + apiKey + "/" + latitude + "," + longitude;

        if (isNetworkAvailable()) {

            //make a new OkHttpClient object
            OkHttpClient client = new OkHttpClient();

            //new request object - method chaining
            Request request = new Request.Builder()
                    .url(forecastURL)
                    .build();

            //make a request from a Call class
            Call call = client.newCall(request);

            //make and asynchronous call with the enqueue method
            call.enqueue(new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {

                }

                @Override
                public void onResponse(Call call, Response response) throws IOException {
                    try {
                        if (response.isSuccessful()) {
                            String jsonData = response.body().string();

                            Log.v(TAG, jsonData);
                            mCurrentWeather = getCurrentDetails(jsonData);
                        } else {
                            alertUserAboutError();

                        }
                    } catch (IOException e) {
                        Log.e(TAG, "Exception caught", e);
                    } catch (JSONException e) {
                        Log.e(TAG, "Exception Caught", e);
                    }
                }


            });
        } else {
            Toast.makeText(this, getString(R.string.network_unavailable_message),
                    Toast.LENGTH_LONG).show();
            //code challenge:  make into Dialog fragment
        }
        //log to console
        Log.d(TAG, "Main UI code is running!");

    }

    private CurrentWeather getCurrentDetails(String jsonData) throws JSONException {

            JSONObject forecast= new JSONObject(jsonData);
            String timezone = forecast.getString("timezone");
            Log.i(TAG, "FROM JSON: " + timezone);

            JSONObject currently = new JSONObject("currently");

            CurrentWeather currentWeather = new CurrentWeather();
            currentWeather.setHumidity(currently.getDouble("humidity"));
            currentWeather.setTime(currently.getLong("time"));
            currentWeather.setIcon(currently.getString("icon"));
            currentWeather.setPrecipChance(currently.getDouble("precipProbability"));
            currentWeather.setSummary(currently.getString("summary"));
            currentWeather.setTemperature(currently.getDouble("temperature"));
            currentWeather.setTimeZone(timezone);
            //return null
            //return new CurrentWeather();

            Log.d(TAG, currentWeather.getFormattedTime());

            return currentWeather;

    }

    private boolean isNetworkAvailable() {
        ConnectivityManager manager= (ConnectivityManager)
                getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = manager.getActiveNetworkInfo();
        boolean isAvailable = false;
        if(networkInfo != null && networkInfo.isConnected()){
            isAvailable = true;

        }

        return isAvailable;
    }

    private void alertUserAboutError() {
        AlertDialogFragment dialog = new AlertDialogFragment();
        dialog.show(getFragmentManager(), "error_dialog");
    }
}