getCount() is being called before BaseAdapter constructor method finishes executing

Question

I am new to android. I am trying to create a GridView consisting of ImageView. The images are from flickr and I am using flickr API to search flickr and receive JSON response. I parse the JSON data to get image URL. The API call and parsing JSON data is done inside FlickrAdapter which extends BaseAdapter. But the problem is my getView() method is never called. I searched stackoverflow for this and I found that if there is no data to show then getView() will not be called. But I am setting the data in FlickrAdapter constructor. I've set some debug texts in the methods and I see that getCount() is called before the data is set which means getCount() is called before the FlickrAdapter constructor finishes executing. So getView() is never called. I want getCount() method to be called after the constructor method of my FlickrAdapter finishes executing. How can I solve this problem?

Here is my code for the BaseAdapter and other classes

FlickrAdapter.java

public class FlickrAdapter extends BaseAdapter {

public ArrayList<FlickrImage> flickrImagesList;
private Context context;

public static  FlickrAdapter instance;
FlickrAdapter(final Context context, String searchText, Activity activity) {
    this.flickrImagesList = new ArrayList<FlickrImage>();
    this.context = context;
    instance = this;
    Flickr flickr = new Flickr(searchText, context, activity);
    //row[0] = inflater.inflate(R.layout.template, null, false);
    Log.d("URL", flickr.buildApiUrl());
    DownloadManager.getJsonResponse(flickr.buildApiUrl(), context, new VolleyCallBack<JSONObject>() {
        @Override
        public void onSuccess(JSONObject success) {
            //Log.d("JSON",success.toString());
            try {
                success = success.getJSONObject("photos");
                JSONArray photo = success.getJSONArray("photo");

                for (int i = 0; i < photo.length(); i++) {
                    JSONObject tempObject = photo.getJSONObject(i);
                    String result = new StringBuilder("https://farm" + tempObject.get("farm").toString() +
                            ".staticflickr.com/" +
                            tempObject.get("server").toString() +
                            "/" +
                            tempObject.get("id").toString() +
                            "_" +
                            tempObject.get("secret").toString() +
                            "_n.jpg").toString();

                    FlickrImage image = new FlickrImage(i, result);
                    instance.flickrImagesList.add(image);

                    Log.d("SIZE", String.valueOf(instance.flickrImagesList.size()));

                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    });
}

@Override
public int getCount() {
    Log.d("COUNT",String.valueOf(flickrImagesList.size()));
    return flickrImagesList.size();
}

@Override
public Object getItem(int position) {
    return flickrImagesList.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

class ViewHolder {
    ImageView myImage;

    ViewHolder(View v) {
        myImage = (ImageView) v.findViewById(R.id.individulaImage);
    }
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View row = convertView;
    ViewHolder holder = null;
    if (row == null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        row = inflater.inflate(R.layout.individual_image, parent, false);
        holder = new ViewHolder(row);
        row.setTag(holder);
    } else {
        holder = (ViewHolder) row.getTag();
    }


    FlickrImage tempImage = flickrImagesList.get(position);
    Log.d("Address", tempImage.imageName);

    //ImageView iv = (ImageView) convertView.findViewById(R.id.individulaImage);

    //Picasso.with(context).load(tempImage.imageName).into(iv);
    return row;
}}

Flickr.java

public class Flickr {
private StringBuilder urlBuilder = new StringBuilder("https://api.flickr.com/services/rest/?method=flickr.photos.search&api_key=e78808f6cf756218d6981fcdf8021f0c&tags=");
private String apiUrl = "";
private Context context = null;
private Activity activity;
private String[] individualImageUrl;
private String keyWord = "";

public Flickr(String keyWord, Context context, Activity activity) {
    this.keyWord=keyWord;
    this.apiUrl = buildApiUrl();
    this.context = context;
    this.activity = activity;
    //Log.d("APIURL", this.apiUrl);
}

public String buildApiUrl() {
    String[] temp;
    StringBuilder sb = new StringBuilder();
    temp = this.keyWord.split(" ");
    for (int i = 0; i < temp.length; i++) {
        sb.append(temp[i]);
        if (i != (temp.length - 1)) {
            sb.append("+");
        }
    }
    urlBuilder.append(sb);
    urlBuilder.append("&text=");
    urlBuilder.append(sb);
    urlBuilder.append("&format=json&nojsoncallback=1");

    return urlBuilder.toString();
}}

FlickrImage.java

public class FlickrImage {
public int imageId;
public String imageName;

FlickrImage(int imageId, String imageURL) {
    this.imageId = imageId;
    this.imageName = imageURL;
    }
}

VolleyCallBack.java

public interface VolleyCallBack<T> {
public void onSuccess(T success);
}

DownloadManager.java

public class DownloadManager {
public static void getJsonResponse(final String Url, Context context, final VolleyCallBack callBack) {
    JsonObjectRequest flickrJsonRequest = new JsonObjectRequest(Request.Method.GET, Url, null,
            new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    callBack.onSuccess(response);
                }
            },
            new Response.ErrorListener() {
                public void onErrorResponse(VolleyError error) {
                    error.printStackTrace();
                }
            });
    Volley.newRequestQueue(context).add(flickrJsonRequest);
}
}

Answer 1

It is not being called before your constructor completes. YOur web code runs in a seperate thread so your constructor code completes and then getCount is called. Once your web code is complete onSuccess is called.

It is never advisable to run network code in adapter. Run it in your activity or fragment and once it completes call notifyDatasetChanged() on your adapter.