應(yīng)公司的需求，需要在沒有觸摸屏只有上下確定和取消的物理按鍵設(shè)備上操作Recyclerview并標(biāo)記出當(dāng)前選中欄(多一嘴，臥槽啊，搞毛啊，省預(yù)算也不是這么省的??！不帶觸摸屏你用QT??！QT效果不好？不帶觸摸屏加物理按鍵效果就好了？！)，做的時候就想當(dāng)然的在bindView里把holder添加到了集合里，然后根據(jù)上下鍵事件往下走改變view，然后，突然很傻比的發(fā)現(xiàn)忽略了最基本的事情，Recyclerview就只會在一開始創(chuàng)建當(dāng)前屏幕顯示數(shù)的holder，并不能獲取到全部的holder，這樣我在按下鍵的時候就只會走到當(dāng)前顯示的最后item上去，下面就再也走不動了。

好吧，開始找方法，大體思路就是動態(tài)的來獲取holder改變布局，但是我需要在外面的物理按鍵回調(diào)里改變Recyclerview里面的view，嗯，一開始還就創(chuàng)建幾個，后面的就不能再onBind里拿到了，再看看有沒有什么其他方法，看見一個，getChildViewHolder(View child),嗯，看方法名很靠譜，但是參數(shù)是view。。。。

好吧，只能進去看看代碼了，從上到下翻了一圈，發(fā)覺有一個方法

    /**
     * Return the ViewHolder for the item in the given position of the data set. Unlike
     * {@link #findViewHolderForLayoutPosition(int)} this method takes into account any pending
     * adapter changes that may not be reflected to the layout yet. On the other hand, if
     * {@link Adapter#notifyDataSetChanged()} has been called but the new layout has not been
     * calculated yet, this method will return <code>null</code> since the new positions of views
     * are unknown until the layout is calculated.
     * <p>
     * This method checks only the children of RecyclerView. If the item at the given
     * <code>position</code> is not laid out, it <em>will not</em> create a new one.
     * <p>
     * When the ItemAnimator is running a change animation, there might be 2 ViewHolders
     * representing the same Item. In this case, the updated ViewHolder will be returned.
     *
     * @param position The position of the item in the data set of the adapter
     * @return The ViewHolder at <code>position</code> or null if there is no such item
     */
    public ViewHolder findViewHolderForAdapterPosition(int position) {
        if (mDataSetHasChangedAfterLayout) {
            return null;
        }
        final int childCount = mChildHelper.getUnfilteredChildCount();
        // hidden VHs are not preferred but if that is the only one we find, we rather return it
        ViewHolder hidden = null;
        for (int i = 0; i < childCount; i++) {
            final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
            if (holder != null && !holder.isRemoved() && getAdapterPositionFor(holder) == position) {
                if (mChildHelper.isHidden(holder.itemView)) {
                    hidden = holder;
                } else {
                    return holder;
                }
            }
        }
        return hidden;
    }

嗯，除了mDataSetHasChangedAfterLayout這個變量看起來有點辣眼，后面明顯就可以獲取到我所需要的holder啊，可以可以，來邊走邊試

rvPsytopicList.scrollToPosition(index);
RecyclerView.ViewHolder viewHolderForAdapterPosition = rvPsytopicList.findViewHolderForAdapterPosition(index);

先讓它滑動到我所需要改變的item，更新holder，然后我獲取holder該干嘛干嘛，嗯，簡直天才。嗯？走到超出屏幕的下一條返回了個null？嗯？繼續(xù)按走到最后再往上走就能獲取到了？這玩意還有延遲不成？好吧。。再進去源碼看吧。

for (int i = 0; i < childCount; i++) {
            final ViewHolder holder = getChildViewHolderInt(mChildHelper.getUnfilteredChildAt(i));
            //這里循環(huán)檢查已存在的holder
            if (holder != null && !holder.isRemoved() && getAdapterPositionFor(holder) == position) {
                if (mChildHelper.isHidden(holder.itemView)) {
                    hidden = holder;
                } else {
                    return holder;
                }
            }
        }

嗯。。。。。并沒有找到為啥，但是看在以上循環(huán)檢查的時候debug知道以前滾過的item的holder是有的，可以，這樣這個需求的難度就是不存在的了兄弟~，立馬改代碼，讓每次多scroll一個角標(biāo)，成功實現(xiàn)！

rvPsytopicList.scrollToPosition(index+1);
RecyclerView.ViewHolder viewHolderForAdapterPosition = rvPsytopicList.findViewHolderForAdapterPosition(index);

(初來乍到，一腳踏入不知深淺，望多多指教！)