Android Empty ViewPager Update with Rest API response

Question

I am using android ViewPager.

I am setting viewpager with empty list in the beginning because I only want to show the dynamic data which I will fetch from REST API response.

So while giving an empty list of adapter. there will be 0 page in the beginning. So beside that I am running AsynTask which will fetch the data in JSON format from server.

I want to set the empty View Pager count with the array size of json response. So total number of pages = size of json array

But When I try to update the adapter. Its does nothing . Stay showing only empty screen.

I am having trouble in updating the view pager.

onPostExecute Method of AsynTask.java

protected void onPostExecute(String result) {
        Log.d("resultOnPostExecute", result);
        //JSONObject data;
        ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String, String>>();
        ////Intent intent = new Intent(getApplicationContext(), ResultActivity.class);
        try {

            if(!result.isEmpty()) {
                JSONObject jObject  = new JSONObject(result);
                //data = jObject;
                Log.d("STATUS", jObject.getString("success"));
                String status = jObject.getString("success").toString();
                if(status.equals("1")) {
                    JSONArray array = jObject.getJSONArray("reports");
                    for (int i = 0; i < array.length(); i++) {
                        JSONObject jo = array.getJSONObject(i);

                        Log.d("id", jo.getString("id"));
                        Log.d("image", jo.getString("image"));

                        images.add(jo.getString("image"));
                        //adapter().notifyDataSetChanged();

                        /*HashMap<String, String> department = new HashMap<>();
                        department.put("id", jo.getString("id"));
                        department.put("name", jo.getString("name"));

                        list.add(department);*/
                    }
                    adapter.updateList(images);

                    ////intent.putExtra("result", result);
                }
                else
                    Toast.makeText(getApplicationContext(), "No doctor found", Toast.LENGTH_LONG).show();
            }
            //// else
            ////       intent.putExtra("result", "NOTHONG FIND");
        } catch (JSONException e) {
            e.printStackTrace();
        }
        //// startActivity(intent);
    }

ViewPagerAdapter.java

package android.hmkcode.com.apicall;
import android.content.Context;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
import java.util.List;
/**
 * Created by umar on 3/7/2016.
 */
public class ViewPagerAdapter extends PagerAdapter {
 Context c;
private ArrayList<String> _imagePaths;
private LayoutInflater inflater;
public ViewPagerAdapter(Context c, ArrayList<String> imagePaths) {
    Log.d("CUEW OAFE ADAORER", "constructor");
    this._imagePaths = imagePaths;
    Log.d("size",this._imagePaths.size()+"");
    this.c = c;
}
@Override
public int getCount() {
    return this._imagePaths.size();
}

@Override
public boolean isViewFromObject(View view, Object object) {
    return view == (object);
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
    ImageView imgDisplay;

    inflater = (LayoutInflater) c
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View viewLayout = inflater.inflate(R.layout.pager_item, container,
            false);

    imgDisplay = (ImageView) viewLayout.findViewById(R.id.image);

    Picasso.with(c).load(_imagePaths.get(position)).into(imgDisplay);
    (container).addView(viewLayout);

    return viewLayout;
}

@Override
public void notifyDataSetChanged() {
    Log.d("NOTFIY STATE CHANGED","NOTIFY STATE CHANGE");
    super.notifyDataSetChanged();
}

@Override
public Parcelable saveState() {
    return null;
}

/*public int getItemPosition(Object object) {
    return POSITION_NONE;
}*/

@Override
public void restoreState(Parcelable state, ClassLoader loader) {

}


@Override
public void destroyItem(ViewGroup container, int position, Object object) {
    (container).removeView((RelativeLayout) object);

}

public void updateList(ArrayList<String> images){
    Log.d("updated list", "list update");
    this._imagePaths = images;
    Log.d("size",this._imagePaths.size()+"");
    this.notifyDataSetChanged();
}
}

Data got updated but UI is still empty.

Every one suggestion is apprreciated.

Thank you all.

Answer 1

1. You need to initialize array as empty and pass to viewpager adapter.
2. your viewpager will be single with empty view
3. when you call AsynTask then add all array items in viewpager adapter and notify if you want to further then post your code.