删除RecyclerView项目

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,则将删除第一个项目并添加新项目.

如果RecyclerView不能再向下滚动,!recyclerView.canScrollVertically(1);那么在添加新项目后,RecyclerView将smoothScroolToPosition()到达最后一个位置.

问题出在哪儿？ 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移除物品时的位置

我尝试过layoutManager.setStackFromEnd(true);但没有运气

有什么建议？

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,我的问题可以重现:

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,您将删除顶部count项目,以便:

notifyItemRangeRemoved(0,count)

应该做的工作.