获取RecyclerView中当前可见的项

Question

我有一个全屏的RecyclerView活动，用于加载图片。用户可以左右滑动以查看下一项（通过LinearSnapHelper实现）。在图片上方，有一个悬浮操作栏，其操作是下载当前可见的图像。

问题是当我点击FAB时，它会下载下一项而不是当前的图像。因为onBindViewHolder提前执行下一项和上一项。如果FAB是项目布局的一部分，则不会出现问题，但在这种情况下，Fab是Activity布局的一部分。

Adapter -

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);
}
}

在活动（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);

                }
            });
        }
    });

- Ankur Gupta

Answer 1

我能想到的解决方案如下。 每当用户滚动时，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) {
                ...
                }
        }
}

- Ankur Gupta

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完美的，谢谢！ - Pratik Tank

llm变量到底是什么？我没有看到定义？ - MathematicsBeginner

我假设 llm 是线性布局管理器。 - Adi Nugroho