RecyclerView 加載更多時遇到的閃爍問題

當用RecyclerView進行加載更多資料的時候，不要使用notifyDataSetChanged()。該方法誰重新整理整體的資料集合，所有的view重新重新整理，出現了閃爍的問題，從源碼進行分析

public abstract static class Adapter<VH extends ViewHolder> {
    ...
     public final void notifyDataSetChanged() {
            mObservable.notifyChanged();
    }
}

 static class AdapterDataObservable extends Observable<AdapterDataObserver> {

     public void notifyChanged() {
            // since onChanged() is implemented by the app, it could do anything, including
            // removing itself from {@link mObservers} - and that could cause problems if
            // an iterator is used on the ArrayList {@link mObservers}.
            // to avoid such problems, just march thru the list in the reverse order.
            for (int i = mObservers.size() - ; i >= ; i--) {
                mObservers.get(i).onChanged();
            }
        }
 }
           

從代碼可以看出來，該方法是對所有的資料進行了重新整理,如果繼續追蹤下去，其實就是更新資料，之後recyclerView調用了requestLayout()方法

RecyclerView其實提供了更好的方法來針對發生了變化的資料

* @see #notifyItemChanged(int)
* @see #notifyItemInserted(int)
* @see #notifyItemRemoved(int)
* @see #notifyItemRangeChanged(int, int)
* @see #notifyItemRangeInserted(int, int)
* @see #notifyItemRangeRemoved(int, int)
           

從名稱就能看出具體的作用了，我們看看常用的方法

/**
     * Notify any registered observers that the <code>itemCount</code> items starting at
     * position <code>positionStart</code> have changed.
     * Equivalent to calling <code>notifyItemRangeChanged(position, itemCount, null);</code>.
     *
     * <p>This is an item change event, not a structural change event. It indicates that
     * any reflection of the data in the given position range is out of date and should
     * be updated. The items in the given range retain the same identity.</p>
     *
     * @param positionStart Position of the first item that has changed
     * @param itemCount Number of items that have changed
     *
     * @see #notifyItemChanged(int)
     */
    public final void notifyItemRangeChanged(int positionStart, int itemCount) {
        mObservable.notifyItemRangeChanged(positionStart, itemCount);
    }
           

不需要多說看看注釋和方法名稱就能體會到他的作用了，他隻會更新從positionStart開始的itemCount的個資料變化，而之前的view和資料是不會發生變化的。

使用該方法就可以解決閃爍問題了

網上有說使用

(recyclerCategory.itemAnimator as SimpleItemAnimator).supportsChangeAnimations = false

來解決閃爍問題的，該方法取消了adapter自帶的動畫效果，但是我測試隻需使用notifyItemRangeChanged就可以解決了，無需進行類似的設定。