RecyclerView 将未选择的项目标记为已选择

Question

My RecyclerView repeats the marked item on Scrolling.

My RecyclerView has 10 Lines which are actually displayed! If I click on the first, its background gets highlighted. If I scroll down now, another item is highlighted!

If I scroll up, the first items isn't highlighted anymore, but another item...

Here's an Image of the Problem:

Any my RecyclerViewAdapter:

public class SelectSongRecyclerViewAdapter extends RecyclerView.Adapter<SelectSongRecyclerViewAdapter.Holder> {
    private Song[] sSongs;
    private List<Song> selectedSongs;

    public SelectSongRecyclerViewAdapter(Song[] songs) {
        sSongs = songs;

        selectedSongs = new ArrayList<>();
    }

    @Override
    public Holder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.adapter_selectsongsview, parent, false);

        Holder holder = new Holder(view);

        return holder;
    }

    @Override
    public void onBindViewHolder(final Holder holder, final int position) {
        //holder.imvSong.setImageResource(R.drawable.standardartwork);
        holder.txvSongTitle.setText(sSongs[position].getTitle());
        holder.txvSongInfo.setText(sSongs[position].getArtists());

        holder.linearLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (selectedSongs.contains(sSongs[position])) {
                    selectedSongs.remove(sSongs[position]);
                    holder.linearLayout.setBackgroundResource(android.R.color.transparent);
                }
                else {
                    selectedSongs.add(sSongs[position]);
                    holder.linearLayout.setBackgroundResource(R.color.colorItemSelected);
                }
            }
        });
    }

    @Override
    public int getItemCount() {
        return sSongs != null ? sSongs.length : 0;
    }

    public Song[] getSelectedSongs() {
        Song[] songs = new Song[selectedSongs.size()];

        return selectedSongs.toArray(songs);
    }

    public class Holder extends RecyclerView.ViewHolder {
        LinearLayout linearLayout;
        ImageView imvSong;
        TextView txvSongTitle;
        TextView txvSongInfo;

        public Holder(View layout) {
            super(layout);

            linearLayout = (LinearLayout) layout;

            imvSong = (ImageView) layout.findViewById(R.id.imvSong);
            txvSongTitle = (TextView) layout.findViewById(R.id.adap_txvSongtitle);
            txvSongInfo = (TextView) layout.findViewById(R.id.adap_txvSongInfo);
        }
    }
}

I hope you can help me! Thanks!

Answer 1

Here my working Code I used!

When onBindViewHolder is called, the items are only selected if they are in the selectedSongs -List!

@Override
public void onBindViewHolder(final Holder holder, int position) {
    holder.txvSongTitle.setText(sSongs[position].getTitle());
    holder.txvSongInfo.setText(sSongs[position].getArtists());

    if (!selectedSongs.contains(sSongs[position])) {
        holder.linearLayout.setBackgroundResource(android.R.color.transparent);
    }
    else {
        holder.linearLayout.setBackgroundResource(R.color.colorItemSelected);
    }

    holder.linearLayout.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            int pos = holder.getAdapterPosition();System.out.println(sSongs[pos].getTitle());

            if (selectedSongs.contains(sSongs[pos])) {
                selectedSongs.remove(sSongs[pos]);

                holder.linearLayout.setBackgroundResource(android.R.color.transparent);
            }
            else {
                selectedSongs.add(sSongs[pos]);

                holder.linearLayout.setBackgroundResource(R.color.colorItemSelected);
            }
        }
    });
}

Answer 2

This is how RecyclerView works: - creates as many Views can fit inside the screen and each time you scroll passes the view to onBindViewHolder in order to update it's data based on the item index

Now when one of the views is clicked you change the background color of the view and when you scroll you pass a view with backgroundColor (colorItemSelected) and just change it's data.

What you should do is onBindViewHolder set view's background color to colorItemSelected if item is selected OR transparent if not.

Here is some co

 public void onBindViewHolder(final Holder holder, final int position) {
    //holder.imvSong.setImageResource(R.drawable.standardartwork);
    holder.txvSongTitle.setText(sSongs[position].getTitle());
    holder.txvSongInfo.setText(sSongs[position].getArtists());
    if (selectedSongs.contains(sSongs[position])) {  
              holder.linearLayout.setBackgroundResource(R.color.colorItemSelected);
    }else {
holder.linearLayout.setBackgroundResource(android.R.color.transparent);
}

    holder.linearLayout.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (selectedSongs.contains(sSongs[position])) {
                selectedSongs.remove(sSongs[position]);
                holder.linearLayout.setBackgroundResource(android.R.color.transparent);
            }
            else {
                selectedSongs.add(sSongs[position]);
                holder.linearLayout.setBackgroundResource(R.color.colorItemSelected);
            }
        }
    });
}

Answer 3

try this adapter,

public class SelectSongRecyclerViewAdapter extends RecyclerView.Adapter<SelectSongRecyclerViewAdapter.Holder> { 
private Song[] sSongs;
private List<Song> selectedSongs;

public SelectSongRecyclerViewAdapter(Song[] songs) {
    sSongs = songs;

    selectedSongs = new ArrayList<>();
} 

@Override 
public Holder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.adapter_selectsongsview, parent, false);

    Holder holder = new Holder(view);

    return holder;
} 

@Override 
public void onBindViewHolder(final Holder holder, final int position) {
    holder.bind(position); 

} 

@Override 
public int getItemCount() { 
    return sSongs != null ? sSongs.length : 0;
} 

public Song[] getSelectedSongs() { 
    Song[] songs = new Song[selectedSongs.size()];

    return selectedSongs.toArray(songs);
} 

public class Holder extends RecyclerView.ViewHolder implements View.OnClickListener {
    LinearLayout linearLayout;
    ImageView imvSong;
    TextView txvSongTitle;
    TextView txvSongInfo;

    public Holder(View layout) {
        super(layout);

        linearLayout = (LinearLayout) layout;

        imvSong = (ImageView) layout.findViewById(R.id.imvSong);
        txvSongTitle = (TextView) layout.findViewById(R.id.adap_txvSongtitle);
        txvSongInfo = (TextView) layout.findViewById(R.id.adap_txvSongInfo);
        linearLayout.setOnClickListener(this);
    }

    public void bind(int position){
        txvSongTitle.setText(sSongs[position].getTitle());
        txvSongInfo.setText(sSongs[position].getArtists());

        if (selectedSongs.contains(sSongs[getAdapterPosition()])) {
            linearLayout.setBackgroundResource(android.R.color.transparent);
        }
        else {
            linearLayout.setBackgroundResource(R.color.colorItemSelected);
        }
    }

    @Override
    public void onClick(View v) {
        if (selectedSongs.contains(sSongs[getAdapterPosition()])) {
            selectedSongs.remove(sSongs[getAdapterPosition()]);
            holder.linearLayout.setBackgroundResource(android.R.color.transparent);
        }
        else {
            selectedSongs.add(sSongs[getAdapterPosition()]);
            holder.linearLayout.setBackgroundResource(R.color.colorItemSelected);
        }
    }
}

}

Answer 4

Change you onBindViewHolder to this

    @Override
        public void onBindViewHolder(final Holder holder, final int position) {
            //holder.imvSong.setImageResource(R.drawable.standardartwork);
            holder.txvSongTitle.setText(sSongs[position].getTitle());
            holder.txvSongInfo.setText(sSongs[position].getArtists());

holder.linearLayout.setBackgroundResource(selectedSongs.contains(sSongs[position]) ? R.color.colorItemSelected : android.R.color.transparent);


            holder.linearLayout.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (selectedSongs.contains(sSongs[position])) {
                        selectedSongs.remove(sSongs[position]);
                        notifyDataSetChanged();
                    }
                    else {
                        selectedSongs.add(sSongs[position]);
                        notifyDataSetChanged();
                    }
                }
            });
        }

Answer 5

Java

private int position = -1;

@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
  holder.itemView.setSelected(holder.getLayoutPosition() == this.position);
  holder.itemView.setOnClickListener(v -> {
     holder.itemView.setSelected(true);
     this.position = holder.getLayoutPosition();
  });
}

Kotlin

val position = -1

fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
    holder.itemView.isSelected = holder.layoutPosition == this.position
    holder.itemView.setOnClickListener { v: View? ->
        holder.itemView.isSelected = true
        this.position = holder.layoutPosition
    }
}

item_background.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_selected="true">
        <shape>
            <solid android:color="@android:color/holo_blue_bright" />
        </shape>
    </item>

    <item>
        <shape>
            <solid android:color="@android:color/white" />
        </shape>
    </item>
</selector>