How to synchronize threads that receive images with url

Issue

I use retrofit2 to Get some string data and image url from the server and recyclerview shows the received data.

I used a thread to get an image with url.

However, since threads are asynchronous, the problem is that the next action is taken while the image is being retrieved by url.

This is the code that I use to retrieve data using retrofit

public void getData(ArrayList<String> IdList, int len) {
    Call<RepoReviewData> call = gitHubService.getReviewListData(IdList);
    call.enqueue(new Callback<RepoReviewData>() {
        @Override
        public void onResponse(Call<RepoReviewData> call, Response<RepoReviewData> response) {
            RepoReviewData repo = response.body();
            String message = repo.getMessage();
            if(message.equals("found")){
                List<RepoReviewData.ReviewList> reviewList = repo.getReviewList();
                reviewDataset.clear();
                for(int i = 0; i < len; i++) {
                    String Id = reviewList.get(i).getUser_Id();
                    ArrayList<String> image_IDs = reviewList.get(i).getReview_Image_List();
                    task.execute(image_IDs);
                }
                    reviewAdapter.addAll(reviewDataset);
                    reviewAdapter.setProgressMore(true);
                    reviewAdapter.setMoreLoading(true);
            }
        }
        @Override
        public void onFailure(Call<RepoReviewData> call, Throwable t) {

        }
    });
}

and this is my asynctask code

private class back extends AsyncTask<String[], Integer,ArrayList<Bitmap>> {
    @Override
    protected ArrayList<Bitmap> doInBackground(String[]... urls) {
        try{
            images = new ArrayList<>();

            int Alen = urls.length;
            for(int i = 0; i<Alen; i++){
                java.net.URL myFileUrl = new URL(urls[i].toString());
                HttpURLConnection conn = (HttpURLConnection)myFileUrl.openConnection();
                conn.setDoInput(true);
                conn.connect();

                InputStream is = conn.getInputStream();
                Bitmap bmImg = BitmapFactory.decodeStream(is);
                images.add(bmImg);
            }
        }catch(IOException e){
            e.printStackTrace();
        }
        return images;
    }

    protected void onPostExecute(ArrayList<Bitmap> img){

    }
}

But it runs asynchronously and does not work the way I want.

I know that I need to update recyclerview with the value returned after the asynctask.

But I do not know how to do it.

If you know how to do this or if you know a good example, I would appreciate it if you let me know.

Thank you for reading and hope you have a good day!

Solution

You don't need to download images and get Bitmap using AsyncTask

You can simply use Glide or Picasso library to load images in your RecyclerView

In your onBindViewHolder holder user below code

@Override 
public void onBindViewHolder(ViewHolder holder, int position) {


        String url = list.get(position).imageurl;
        Glide.with(context) 
                .load(url)
                .placeholder(R.drawable.piwo_48)
                .transform(new CircleTransform(context)) 
                .into(holder.imageView);

} 

Hope this will help

Answered By - Parvinder Maan