[SOLVED] Alert Dialogs not working

package uk.co.jonniegrieve.stormy;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import java.io.IOException;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity {

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

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

        String apiKey = "c967557031449620255ff3c64b443a26";

        double latitude = 99999; //37.8267;
        double longitude = -122.4233;

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



        //The request

        OkHttpClient client = new OkHttpClient();

        Request request = new Request.Builder()
                .url(forecastURL)
                .build();

        Call call = client.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {

            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {

                try {

                    Log.v(TAG, response.body().string());

                    if(response.isSuccessful()) {

                    }
                } catch (IOException e) {
                    alertUserAboutError();
                }
            }
        });

        Log.d(TAG, "Main UI code is running! Hooray");

    }

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

}

package uk.co.jonniegrieve.stormy;

import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.Context;
import android.os.Bundle;

public class AlertDialogFragment extends DialogFragment {
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        Context context = getActivity();
        AlertDialog.Builder builder = new AlertDialog.Builder(context);

        //alert dialog box

        builder.setTitle(R.string.error_title)
        .setMessage(R.string.error_message)
        .setPositiveButton( R.string.error_btn_ok_txt, null);

        return builder.create();

    }
}