Doing some network operation inside an Adapter

Question

I am developing an application for android on which I have a listview displaying some Users. Thus I want to display their pictures inside this list view so I do as follow:

private class StableArrayAdapter extends ArrayAdapter<Request>{
    private Context context;
    private Bitmap tempobmp;
    private List<User> mylist;
    public StableArrayAdapter(Context context,List<User> mylist){
        super(context, R.layout.request_layout, mylist);
        this.context = context;
        this.mylist = mylist;
    }
    public class ViewHolder{
        public ImageView image;
      }
    public View getView(int position,View convertView,ViewGroup parent){
        View vi = convertView;
        if(vi==null){
            ViewHolder holder = new ViewHolder()
            holder.image = (ImageView) vi.findViewById(R.id.requestImage);
        }
        final ViewHolder holder = (ViewHolder) vi.getTag();
        User s = mylist.get(position);
        try{

            final URL url = new URL(myapp.getUser().getPhoto().getS3Url());
            Thread thread = new Thread(new Runnable() {
                  @Override
                  public void run() {
                      try{
                        InputStream is = (InputStream) url.getContent();

                        Bitmap bmp = BitmapFactory.decodeStream(is);

                        tempobmp=bmp;

                      }
                      catch(Exception e){
                          Log.d("eeeeA52","eeeeA52"+e);
                      }
                  }
            });
            thread.start(); 
            thread.wait();

        }
        catch(Exception e){
            Log.d("eeeeAF","eeeeAF"+e);
        }
        holder.image.setImageBitmap(tempobmp);
      return vi;
    }

All the logs I can put inside my thread tell me that it has no problems to get the bitmap from my database but when I launch the page with this ListView the image are still the default ones. Is it possible to use a thread in adapter in the way to retrieve network datas? If yes which is the best practice for it?

Thank you guys :)

it will be very performance cost and try to void long processing in adpater , try to making list of user and list of their image before creating the Listview — mohammed momn, Jan 20 '14 at 00:40
You can use AsyncTask for that, since it allows you to do some longer processing in a background thread and conveniently apply the result on the UI thread. That's also possible from within an adapter. When the background operation has finished then you can call notifyDataSetChanged on the adapter to make the changes visible. Make sure that you do NOT update the internal adapter state (that may be used for rendering views such as item count etc.) from your background thread. It is only safe to do these changes on the UI thread. — tiguchi, Jan 20 '14 at 00:46
So I should update my UI variable in onPostExecute methode of my AsyncTask? — Pclaverie, Jan 20 '14 at 00:50
take look this thread may help you understand in more details http://stackoverflow.com/questions/6244330/is-arrayadapter-thread-safe-in-android-if-not-what-can-i-do-to-make-it-thread — mohammed momn, Jan 20 '14 at 00:59

score 2 · Accepted Answer · answered Jan 20 '14 at 00:47

Generally, it's considered a bad idea to make network calls directly from the Adapter. but If you are actually unable to perform your downloads in your activity/fragment prior to populating your listview, you can use one of the many libraries that do this like Volley that has a networkimageview object just for that. Or you can use the Picasso library that is build specifically for downloading images from the net and displaying in a regular imageView

Both are well documented and easy to use. (Picasso requires 1 line of code)

Doing some network operation inside an Adapter

1 Answers1