I am totally stuck and don't know what to do

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);
      builder.setTitle("Sorry!")
        .setMessage("Try again!")
        .setPositiveButton("OK",null);

        // Insert code here!

        return null;
    }
}

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import java.io.IOException;

public class MovieActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_movie);

        // Get some movie information!
        String apiUrl = "http://api.rottentomatoes.com/api/public/v1.0/movies.json?apikey=xyz&q=hobbit";
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder()
                .url(apiUrl)
                .build();

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


            }

            @Override
            public void onResponse(Response response) throws IOException { }
        });
    }
}