Question

我有一个RecyclerView，它在每个特定时期添加项目。添加对象时，如果列表项超过（假设）500，那么将删除第一个项目并添加新项目。

如果RecyclerView无法向下滚动!recyclerView.canScrollVertically(1);，则在添加新项目后，RecyclerView将smoothScroolToPosition()移至最后位置。

问题出在哪里？ 好吧，如果ReyclerView在移除旧物品时位于中间（不是底部，而不是顶部），它会突然跳起一些位置。我希望RecyclerView不会跳转位置并保持在顶部删除项目时的位置

我尝试使用layoutManager.setStackFromEnd(true);，但没有运气

有什么建议吗？

一些代码（不相关的代码被删除）。当RecyclerView从中间显示列表项并按VOLUME_UP：

时，可以重现我的问题

public class ActivityMain extends ActionBarActivity {

    public static final int MAX_LOG_ITEMS = 500;

    private RecyclerView mRecyclerView;
    private AdapterLog mRecyclerAdapter;
    private boolean mAutoScroll = true;

    private DataReceiver mDataReceiver;
    private Handler mLogHandler = new Handler() {
        @Override public void handleMessage(Message msg) {
            switch (msg.what){
                case DataReceiver.CAT_LOGS:
                    List<Log> catLogs = (List<Log>) msg.obj;
                    updateLogs(catLogs);
                    break;
                case DataReceiver .CLEAR_LOGS:
                    if (mRecyclerAdapter.getItemCount() > MAX_LOG_ITEMS)
                        mRecyclerAdapter.removeFirstItems(mRecyclerAdapter.getItemCount() - MAX_LOG_ITEMS);
                    break;
                case Logcat.REMOVE_LOGS:
                    mRecyclerAdapter.clear();
            }
        }

    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        final LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        layoutManager.setStackFromEnd(true);
        mRecyclerAdapter = new AdapterLog();

        mRecyclerView = (RecyclerView) findViewById(R.id.activity_main_recyclerview);
        mRecyclerView.setHasFixedSize(true);        
        mRecyclerView.setLayoutManager(layoutManager);
        mRecyclerView.setAdapter(mRecyclerAdapter);
        mRecyclerView.setOnScrollListener(new UIUtils.ScrollManager(toolbarContainer != null ?
                toolbarContainer : toolbar){
                @Override public void onScrolled(RecyclerView r, int dx, int dy) {
                    super.onScrolled(r, dx, dy);
                    mAutoScroll = !r.canScrollVertically(1);
                    }
                });
    }



    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        switch(keyCode){
            case KeyEvent.KEYCODE_VOLUME_UP:
//                mAutoScroll = false;
//                mRecyclerView.scrollToPosition(0);
//                if (mRecyclerAdapter.getItemCount() > MAX_LOG_ITEMS)
                    mRecyclerAdapter.removeFirstItems(mRecyclerAdapter.getItemCount() - 50);

                return true;
            case KeyEvent.KEYCODE_VOLUME_DOWN:
                mAutoScroll = true;
                mRecyclerView.scrollToPosition(mRecyclerAdapter.getItemCount() -1);
                return true;
        }
        return false;
    }

    private void updateLogs(final List<Log> logList) {
        final boolean scroll = mAutoScroll;
        mRecyclerAdapter.addAll(logList);
        if (scroll) mRecyclerView.smoothScrollToPosition(mRecyclerAdapter.getItemCount() - 1);
    }

}

RecyclerAdapter：

public class AdapterLog extends RecyclerView.Adapter<AdapterLog.ViewHolder> {

    private final List<Log> mLogList;

    public AdapterLog() {
        this.mLogList = new ArrayList<Log>();
    }

    @Override
    public AdapterLog.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.listitem_log, parent, false);
        return new ViewHolder(v);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.mTextView.setText(getItem(position).getMessage());
        holder.mTextView.setTextColor(getItem(position).getLevel().getColor());
    }

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

    public Log getItem(int position) {
        return mLogList.get(position);
    }

    public void addAll(List<Log> logList) {
        mLogList.addAll(logList);
        notifyDataSetChanged();
    }

    public void removeFirstItems(int count) {
        for (int i=0; i<count; i++) mLogList.remove(0);
        notifyDataSetChanged();
    }

    public void clear() {
        mLogList.clear();
        notifyDataSetChanged();
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView mTextView;
        public ViewHolder(View v) {
            super(v);
            mTextView = (TextView) v.findViewById(R.id.listitem_log_textview);
        }
    }
}

Answer 1

您告诉您的观点是您更改了整个适配器。对于添加，删除和重新排序，请考虑使用以下方法：

notifyItemRangeChanged
notifyItemRangeInserted
notifyItemRangeRemoved
notifyItemMoved
notifyItemInserted
notifyItemChanged
notifyItemRemoved

因此，在您的情况下，您要移除顶级count项：

notifyItemRangeRemoved(0,count)

应该做的工作。

Answer 2

public class viewHolderFav extends RecyclerView.ViewHolder {
    private ImageView image;
    private TextView name;




public viewHolderFav( View itemView ) {
        super( itemView );
        image = ( ImageView ) itemView.findViewById( R.id.txt_image_fav );
        name = ( TextView ) itemView.findViewById( R.id.txt_name_fav );



        edite.setOnClickListener( new View.OnClickListener( ) {
            @Override
            public void onClick( View v ) {

            remove( posts.get( getLayoutPosition() ) );


            }
        } );



    }



public void remove(DataBoj item) {
    int position = posts.indexOf(item);
    posts.remove(position);
    notifyItemRemoved(position);
}

删除RecyclerView项目

2 个答案: