AlertDialogFragment

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);
        AlertDialog dialog = builder.create();

        return dialog;
    }
}

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 { 
            try { 
              Log.v(TAG, response.body().string());
              if (response.isSuccessful());
            }
              else{
                alertUserAboutError();
                }
            } catch (IOException e) {
              Log.e(TAG, "Exception caught: ", e);
            }
        }
        });
        Log.d(TAG, "Main UI code is running!");
    }
      private void alertUserAboutError() {
       AlertDialogFragment dialog = new AlertDialogFragment();
        dialog.show(getFragmentManager(), "error_dialog");
    }
}