android - 在 RecyclerView 中获取当前可见项目

Question

我有一个全屏 RecyclerView 加载图像的 Activity 。用户可以左右滑动以查看下一个项目(通过 LinearSnapHelper 实现)在图像上方，它有 float 操作栏，其操作是下载当前可见的图像。

问题是当我单击 FAB 时，它没有下载当前图像而是下载下一个项目。因为 onBindViewHolder 会针对下一项和上一项提前执行。当 FAB 是项布局的一部分时不会出现问题，但在这种情况下 Fab 是 Activity 布局的一部分。

适配器-

public class FullWallAdapter extends RecyclerView.Adapter<FullscreenViewHolder> {

private ArrayList<String> mWallKeys;
private OnFullSetupViewListener mOnFullSetupViewListener;

public FullWallAdapter(ArrayList<String> wallKeys, OnFullSetupViewListener listener) {
    this.mWallKeys = wallKeys;
    this.mOnFullSetupViewListener = listener;
}

@Override
public FullscreenViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.fullscreen_wallpaper_preview, parent, false);
    return new FullscreenViewHolder(itemView);
}

@Override
public void onBindViewHolder(final FullscreenViewHolder holder, int position) {
    ValueEventListener wallListener = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            ImageModel image = dataSnapshot.getValue(ImageModel.class);
            mOnFullSetupViewListener.onSetupView(holder, image, holder.getAdapterPosition(), dataSnapshot.getKey());

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.e("WallAdapter", "Error occurred: " + databaseError.getMessage());
        }
    };
    DatabaseReference ref = FireUtils.getWallpapersRef().child(mWallKeys.get(position));
    ref.addValueEventListener(wallListener);
    holder.mWallRef = ref;
    holder.mWallListener = wallListener;
}

@Override
public int getItemCount() {
    return mWallKeys.size();
}

@Override
public void onViewRecycled(FullscreenViewHolder holder) {
    super.onViewRecycled(holder);
    if (holder.mWallListener != null)
        holder.mWallRef.removeEventListener(holder.mWallListener);
}

public interface OnFullSetupViewListener {
    void onSetupView(FullscreenViewHolder holder, ImageModel image, int position, String wallKey);
}
}

Activity 中-

FullWallAdapter adapter = new FullWallAdapter(wallKeys, new FullWallAdapter.OnFullSetupViewListener() {
        @Override
        public void onSetupView(final FullscreenViewHolder holder, final ImageModel image,
                                int position, final String wallKey) {
            holder.setImageView(image);

            downloadFab.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    incrementDownload(wallKey, image);
                    String params;
                    params = wallpaper.getPhotoJson();
                    fetchSave(params);

                }
            });
        }
    });

Answer 1

我只能想到如下解决方案。每次用户滚动时触发 onClickListener。

recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            currentPosition = llm.findFirstVisibleItemPosition();
            downloadFab.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                ...
                }
        }
}