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问题:
I am using a RecyclerView with ListAdapter (which uses AsyncListDiffer to calculate and animate changes when list is replaced).
The problem is that if I submit() some list, then re-order that list, and submit() again, nothing happens.
How do I force ListAdapter to evaluate this new list, even though it is "the same" (but order has changed)?
New findings:
I checked source code of submitList() and in the beggining there is a check:
public void submitList(@Nullable final List<T> newList) { final int runGeneration = ++this.mMaxScheduledGeneration; if (newList != this.mList) {
I think this is the problem. But how to get past it? I mean, surely the developers thought about submiting a different ordered list?
回答1:
That function will not get called because ListAdapter won't consider it as another list, since it has all the same items only the order got changed.
@Override public void submitList(@Nullable final List<T> list) { super.submitList(list != null ? new ArrayList<>(list) : null); }
So to solve this, you need to call this function with null first, then immediately call with the order changed list.
submitList(null); submitList(orderChangedList);
回答2:
It defeats ListAdapter's purpose for automatically calculating and animating list changes when you call these lines consecutively:
submitList(null); submitList(orderChangedList);
Meaning, you only cleared (null) the ListAdapter's currentList and then submitted ( .submitList()) a new List. Thus, no corresponding animation will be seen in this case but only a refresh of the entire RecyclerView.
Solution is to implement the .submitList( List<T> list) method inside your ListAdapter as follows:
public void submitList(@Nullable List<T> list) { mDiffer.submitList(list != null ? new ArrayList<>(list) : null); }
This way you allow the ListAdapter to retain its currentList and have it "diffed" with the newList, thereby the calculated animations, as opposed to "diffing" with a null.
Note: However, no update animation will happen, if, of course, the newList contains the same items in the same order as the originalList.
