This presentation is about RecyclerView and special features which can make work with it even better: Adapter, LayoutManager, ItemAnimator, ItemDecoration etc. Presentation by Oleksandr Kravchenko (Software Engineer, GlobalLogic, Lviv), delivered at Mobile TechTalk Lviv on April 28, 2015. More details - http://globallogic.com.ua/mobile-techtalk-lviv-2015-report

1. ©2015 GlobalLogic Inc. CONFIDENTIAL

2. ©2015 GlobalLogic Inc. CONFIDENTIAL
RecyclerView

3. CONFIDENTIAL
Agenda
1. ListView vs LinearLayout
2. Adapter
3. ItemDecoration
4. ItemAnimator
5. LayoutManager
6. Q&A

4. CONFIDENTIAL©2015 GlobalLogic Inc.
ListView vs LinearLayout

5. CONFIDENTIAL
ListView vs LinearLayout
LinearLayout ListView

6. CONFIDENTIAL©2015 GlobalLogic Inc.
Adapter

7. CONFIDENTIAL
RecyclerView.Adapter<ViewHolder>
@Override
public int getItemCount() {
return mData.size();
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item_layout, viewGroup, false);
// initializing view’s listeners
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder viewHolder, int position) {
viewHolder.update(mData.get(position));
}

8. CONFIDENTIAL©2015 GlobalLogic Inc.
ItemDecoration

9. CONFIDENTIAL
RecyclerView.ItemDecoration
Item #2
Item #1
Item #2
Item #1
Item #2
Item #1
@Override
public void onDraw(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
// drawing under the views
}
@Override
public void onDrawOver(Canvas canvas, RecyclerView parent, RecyclerView.State state) {
// drawing over the views
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
// adding extra paddings to the view
}

10. CONFIDENTIAL©2015 GlobalLogic Inc.
ItemAnimator

11. CONFIDENTIAL
RecyclerView.ItemAnimator
● DefaultItemAnimator
● Call notifyItemXXXX() instead of notifyDataSetInvalidated()
● Custom ItemAnimator

12. CONFIDENTIAL
RecyclerView.ItemAnimator
Custom ItemAnimator:
● animateXXXX()
● runPendingAnimations()
● endAnimation(), endAnimations()
*do not forget to call dispatchXXXFinished()

13. CONFIDENTIAL
RecyclerView.ItemAnimator
public boolean animateAdd(final ViewHolder holder) {
endAnimation(holder);
mPendingAdditions.add(holder);
return true;
}
public void runPendingAnimations() {
...
if (!mPendingAdditions.isEmpty()) {
final ArrayList<ViewHolder> additions = new ArrayList<ViewHolder>();
additions.addAll(mPendingAdditions);
mAdditionsList.add(additions);
mPendingAdditions.clear();
for (ViewHolder holder : additions) {
animateAddImpl(holder);
}
additions.clear();
mAdditionsList.remove(additions);
}
}

14. CONFIDENTIAL©2015 GlobalLogic Inc.
LayoutManager

15. CONFIDENTIAL
RecyclerView.LayoutManager
Predefined LayoutManagers:
● LinearLayoutManager: horizontal and vertical
● StaggeredGridLayoutManager
● GridLayoutManager
● Custom LayoutManager

16. CONFIDENTIAL
RecyclerView.LayoutManager
Custom LayoutManager:
● generateDefaultLayoutParams()
● onLayoutChildren()
● canScrollHorizontally() & canScrollVertically()
● scrollHorizontallyBy() & scrollVerticallyBy()
● offsetChildrenHorizontal() & offsetChildrenVertical()
● layoutDecorated(), getDecoratedXXXX()

17. CONFIDENTIAL
RecyclerView.LayoutManager
A BB C D E
Remove item animation:
A C D E F

18. CONFIDENTIAL
RecyclerView.LayoutManager
● supportsPredictiveItemAnimations()
● onLayoutChildren()
● RecyclerView.State.isPreLayout()
● LayoutParams.isItemRemoved()
Remove item animation:
A B C D E FA FC D E

19. CONFIDENTIAL
RecyclerView.LayoutManager
Insert item animation:
A B C D EA B C DX

20. CONFIDENTIAL
RecyclerView.LayoutManager
● getScrapList()
● addDisappearingView() instead of addView()
Insert item animation:
A B C D EA EB C DX

21. CONFIDENTIAL©2015 GlobalLogic Inc.
Q&A

22. CONFIDENTIAL©2015 GlobalLogic Inc.
Alexander Kravchenko
Thank You!