RecyclerView的notifyItemRemoved()方法删除条目问题

来源：互联网发布：mac卸载java8 编辑：程序博客网时间：2024/05/19 20:47

在使用RecyclerView进行开发时，使用notifyItemRemoved()方法删除条目和notifyItemMoved()方法移动条目，遇到删除和移动的条目出现紊乱。

1.删除

本来是删除条目3，没想到结果却是删除了条目4。

在RecyclerView中，并没有提供条目点击监听接口，所以只得在 public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position)方法中通过holder.itemView.setOnLongClickListener()和holder.itemView.setOnClickListener()来监听条目长按和点击事件，关于点击的条目位置是通过参数position来确定的，查看onBindViewHolder()方法的注释：

   /**         * Called by RecyclerView to display the data at the specified position. This method         * should update the contents of the {@link ViewHolder#itemView} to reflect the item at         * the given position.         * <p>         * Note that unlike {@link android.widget.ListView}, RecyclerView will not call this         * method again if the position of the item changes in the data set unless the item itself         * is invalidated or the new position cannot be determined. For this reason, you should only         * use the <code>position</code> parameter while acquiring the related data item inside this         * method and should not keep a copy of it. If you need the position of an item later on         * (e.g. in a click listener), use {@link ViewHolder#getPosition()} which will have the         * updated position.         *         * @param holder The ViewHolder which should be updated to represent the contents of the         *               item at the given position in the data set.         * @param position The position of the item within the adapter's data set.         */        public abstract void onBindViewHolder(VH holder, int position);

从中知道，如果需要监听条目点击的事件，使用ViewHolder的getLayoutPosition()（getPosition()被抛弃）方法才能获得更新后的条目位置，因此：

 holder.itemView.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                holder.getPosition();//not position            }        });

传入的条目位置索引应该使用getLayoutPosition()（getPosition()被抛弃）方法来获取，这样就不会出现条目紊乱。

2.置顶

置顶之后，再滑动，条目变回原来的顺序，查看notifyItemMoved()方法的注释：

 /**         * Notify any registered observers that the item reflected at <code>fromPosition</code>         * has been moved to <code>toPosition</code>.         *         * <p>This is a structural change event. Representations of other existing items in the         * data set are still considered up to date and will not be rebound, though their         * positions may be altered.</p>         *         * @param fromPosition Previous position of the item.         * @param toPosition New position of the item.         */        public final void notifyItemMoved(int fromPosition, int toPosition) {            mObservable.notifyItemMoved(fromPosition, toPosition);        }

尽管条目的位置改变了，但是数据集仍然不会改变，因此需要改变数据集，才能让条目的位置真正改变。

 int position = holder.getPosition();                    String object = mDatas.get(position);                    mDatas.remove(position);                    mDatas.add(0,object);                    notifyItemMoved(position, 0);

1 0