ArrayAdapter getView called continuously

Issue

I have a listview which is showing some images. To avoid UI blocks, I tried to lazy load the thumbnails with an asyncTask in my adapter since that seemed the best solution I found here on SO.

This listView has also an onItemclick and an onItemLongClick listeners.

For some reason, my app is getting really slow down, expecially after performing an onlongclick action. The only thing I found unusual is that my ListView is calling the getView method in loop, never stopping.

Some code:

Adapter

public class FotoGridAdapter extends ArrayAdapter {
    private Context context;
    private int layoutResourceId;
    private ArrayList<WorkorderPicture> workorderPictures = new ArrayList<WorkorderPicture>();

    public FotoGridAdapter(Context context, int layoutResourceId, List<WorkorderPicture> pictures) {
        super(context, layoutResourceId, pictures);
        this.layoutResourceId = layoutResourceId;
        this.context = context;
        this.workorderPictures = new ArrayList<>(pictures);
    }

    @Override
    @Nullable
    public WorkorderPicture getItem(int position) {
        return workorderPictures.get(position);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;
        ViewHolder holder;

        if (row == null) {
            LayoutInflater inflater = ((Activity) context).getLayoutInflater();
            row = inflater.inflate(layoutResourceId, parent, false);
            holder = new ViewHolder();
            holder.imageTitle = row.findViewById(R.id.text);
            holder.image = row.findViewById(R.id.image);
            row.setTag(holder);
        } else {
            holder = (ViewHolder) row.getTag();
        }

        WorkorderPicture workorderPicture = workorderPictures.get(position);
        if (workorderPicture != null) {
            String text = workorderPicture.getTITLE();
            if (workorderPicture.getPHOTODATE() != null) {
                text += " - ";
                text += new SimpleDateFormat("dd/MM/yyyy", Locale.getDefault()).format(workorderPicture.getPHOTODATE());
            }
            holder.imageTitle.setText(text);
            String format = AttachmentUtils.getExtensionFromFileName(workorderPicture.getFILE_NAME_WITH_EXTENSION());
            if (format == null)
                format = "default";
            switch (format.toLowerCase()) {
                case "image/jpeg":
                case "image/png":
                    if (workorderPicture.getPHOTOSTREAM() != null) {
                        new ImageGridHandler(context, holder.image, workorderPicture.getPHOTOSTREAM(), workorderPicture.getPHOTOSTREAM().length).executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
//                        holder.image.setImageBitmap(sbm);
                    } else {
                        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                            holder.image.setImageDrawable(getContext().getDrawable(R.drawable.ic_image));
                        } else {
                            holder.image.setImageDrawable(getContext().getResources().getDrawable(R.drawable.ic_image));
                        }
                    }
                    break;
                case "application/pdf":
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                        holder.image.setImageDrawable(getContext().getDrawable(R.drawable.ic_pdf));
                    } else {
                        holder.image.setImageDrawable(getContext().getResources().getDrawable(R.drawable.ic_pdf));
                    }
                    break;
                default:
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                        holder.image.setImageDrawable(getContext().getDrawable(R.drawable.ic_empty_image));
                    } else {
                        holder.image.setImageDrawable(getContext().getResources().getDrawable(R.drawable.ic_empty_image));
                    }
                    break;

            }

        }
        return row;
    }

    static class ViewHolder {
        TextView imageTitle;
        ImageView image;
    }

    class ImageGridHandler extends AsyncTask<String, Void, Bitmap> {
        private final WeakReference<ImageView> imageViewReference;
        private Context context;
        private byte[] photoStream;
        private int length;

        public ImageGridHandler(Context context, ImageView img, byte[] photoStream, int length) {
            imageViewReference = new WeakReference<>(img);
            this.context = context;
            this.photoStream = photoStream;
            this.length = length;
        }

        @Override
        protected Bitmap doInBackground(String... params) {
            Bitmap bm = BitmapFactory.decodeByteArray(photoStream, 0, length);
            return ThumbnailUtils.extractThumbnail(bm, 80, 100);

        }

        @Override
        protected void onPostExecute(Bitmap result) {
            final ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                imageView.setImageBitmap(result);
                FotoGridAdapter.this.notifyDataSetChanged();
            }
            this.cancel(true);
        }
    }
}

Listeners

    gridView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener()
    {
        @Override
        public boolean onItemLongClick(AdapterView<?> adapterView, View view,
                                       final int position, long l) {
            AlertDialog.Builder builder = new AlertDialog.Builder(getContext(), R.style.myAlertDialogTheme)
                    .setNegativeButton("Annulla", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            dialogInterface.dismiss();
                        }
                    })
                    .setPositiveButton("Elimina", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int i) {
                            final String wpID = openedIntervention.getWorkorderPictures().get(position).getID();
                            realm.executeTransactionAsync(new Realm.Transaction() {
                                @Override
                                public void execute(Realm realm) {
                                    realm.where(WorkorderPicture.class).equalTo("ID", wpID).findFirst().setDELETED(true);
                                }
                            }, new Realm.Transaction.OnSuccess() {
                                @Override
                                public void onSuccess() {
                                    openedIntervention.setWorkorderPictures(realm.where(WorkorderPicture.class)
                                            .equalTo("WORKORDER_ID", openedIntervention.getWorkorder()
                                                    .getID())
                                            .equalTo("DELETED", false)
                                            .findAll());

                                    loadData();
                                }
                            }, new Realm.Transaction.OnError() {
                                @Override
                                public void onError(Throwable error) {

                                }
                            });
                        }
                    }).setTitle(app_name)
                    .setMessage("Eliminare l'allegato selezionato?");
            builder.show();
            return true;
        }
    });

    gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, final int position,
                                long id) {
          //code to show a preview
        }});

Another info might be that I use Realm, but my pictures are unlinked from it, so I don't think it matter

Solution

AsyncTask is asynchronous and after every completion of task, your are notifying the adapter which is causing the data change event so

@Override
protected void onPostExecute(Bitmap result) {
    final ImageView imageView = imageViewReference.get();
    if (imageView != null) {
        imageView.setImageBitmap(result);
        // FotoGridAdapter.this.notifyDataSetChanged();
        // ^^^^^^^^^^^^^^^^ remove this
        // not required in case of change in imageview
    }
    this.cancel(true);
}

Answered By - Pavneet_Singh