Htykuut

In my app, I have a RecyclerView containing (on my phone) about 700 song titles with band names. Nothing too crazy, but reloading this all on the UI thread caused a little lag. I decided to do the loading in an Asynctask, away from the UI thread. This is what it looks like:

 public class PhotoAlbumAdapter : RecyclerView.Adapter

    {

        public List<MP3objectSmall> mp3Obj;

        Context ctx;

        Activity act;

        MediaMetadataRetriever reader;

        DataBase db;

        List<SeekObj> seekObj;

        Typeface tf;

        AudioManager audioManager;





        public PhotoAlbumAdapter(List<MP3objectSmall> mp3Obj, Context ctx, DataBase db, List<SeekObj> seekObj, AudioManager audioManager, Activity act)

        {



            this.mp3Obj = mp3Obj;

            this.ctx = ctx;

            this.db = db;

            this.seekObj = seekObj;

            this.act = act;

            this.audioManager = audioManager;

            reader = new MediaMetadataRetriever();



            tf = Typeface.CreateFromAsset(ctx.Assets, "Baiti.ttf");

        }



        public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)

        {

            View itemView = LayoutInflater.From(parent.Context).

                        Inflate(Resource.Layout.CardView, parent, false);

            PhotoViewHolder vh = new PhotoViewHolder(itemView, mp3Obj, act, reader, db, seekObj, audioManager, ctx);

            return vh;

        }



        public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)

        {

            PhotoViewHolder vh = holder as PhotoViewHolder;







            SetContent(vh, position);





        }



        private async void SetContent(PhotoViewHolder vh, int position)

        {

            await SetContentAsync(vh, position);

        }



        public override int ItemCount

        {



            get

            {

                if (mp3Obj != null)

                {

                    return mp3Obj.Count();

                }

                else

                    return 0;

            }

        }



        private async Task SetContentAsync(PhotoViewHolder vh, int position)

        {

            string SongName = "";

            string ArtistName = "";



            await Task.Run(() =>

            {

                try

                {

                    reader.SetDataSource(mp3Obj[position].Mp3Uri);

                }

                catch

                {



                }



                SongName = reader.ExtractMetadata(MediaMetadataRetriever.MetadataKeyTitle);

                ArtistName = reader.ExtractMetadata(MediaMetadataRetriever.MetadataKeyArtist);

            });



            ((Activity)ctx).RunOnUiThread(() =>

            {

                vh.SongName.SetTypeface(tf, TypefaceStyle.Normal);

                vh.AristName.SetTypeface(tf, TypefaceStyle.Normal);

                vh.SongName.Text = SongName;

                vh.AristName.Text = ArtistName;

            });

        }

    }

This did infact smooth the overall performance up quite a lot but caused some weird side effect:

When I scrolling down the list fast and then stop it appruptley I see the same song 2-3 times in a row. Only one of those items is the song itself, the others are different songs but with the wrong song and artist name on top of them.

If I now scroll up just ever so slightly that the doubling items are out just off the screen and then scroll back the RecyclerView seems to have corrected itself and the doubled or sometimes tripled items are gone.

This issue only occurs since I moved the loading into an Async-task. Did I maybe do something wrong here?

I think the point here is to keep references of the viewHolder.

I would suggest you to try an approach like that:

public class PhotoViewHolder extends RecyclerView.ViewHolder {

    private TextView tvSongName;



    public PhotoViewHolder(View v) {

        super(v);

        //initialize here views; ie

        //this.tvSongName = v.findViewById(R.id.tvSongName);

    }



    public void initializeAsync(int position) {

        Handler mHandler = new Handler();

        new Thread(new Runnable() {



            String songName, otherStuff;



          @Override

          public void run () {

            // here we are async.



            // Retrieve here your song informations, ie:

            //object myRetrievedObject = getSongInfoBasedOnPositionSomeHow(); 

            //songName = myRetrievedObject.retrievedSongName;

            //otherStuff = myRetrievedObject.retrievedOtherStuffs;



            mHandler.post(new Runnable() {

             @Override

             public void run () {

               // make operation on UI

                tvSongName.setText(songName);

                //...

                //...

             }

            });

          }

        }).start();

    }

}

And call this like:

    public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)

    {

        PhotoViewHolder vh = holder as PhotoViewHolder;

        vh.initializeAsync(position);

    }

Please consider that I wrote that without the compiler so it might be not perfect, let me know in any case.

Hope this helps!

I think the arraylist is getting populated twice.so Just before loading arraylist once again in your activity class use yourarraylistname.clear(); to clear the arraylist and then load the data next tym.So whenever you populate the arraylist again it will first get cleared then load the data once again.