recycler_view.pdf

Transcript

1. Recycler View
2. About me contact@vladds.com Lead software engineer Vladislav Matelski Icons made by Freepik from Flaticon are licensed by CC 3.0 BY
3. Agenda Tips & Tricks RecyclerView components ListView Icons made by Freepik from Flaticon are licensed by CC 3.0 BY
4. • complexity overdraft • duplicate features • animations • more complex layouts: GridView, Horizontal ListView, StaggeredGridView ListView Icons made by Freepik from Flaticon are licensed by CC 3.0 BY
5. April 2015 RecyclerView Icons made by Freepik from Flaticon are licensed by CC 3.0 BY
6. RecyclerView LayoutManager ItemAnimator Adapter Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler
7. ItemAnimator Adapter Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler LayoutManager
8. LayoutManager Positioning Scroll Focus Traversal
9. Positioning
10. LayoutManager Positioning Scroll Focus Traversal
11. Scroll Focus Traversal • vertical list • android:state_focused=“true” • TAB and SPACE on a keyboard
12. LayoutManager Positioning Scroll Focus Traversal
13. LayoutManager Mastering RecyclerView Layouts https://youtu.be/gs_C1E8HwvE
14. LayoutManager ItemAnimator Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler Adapter
15. ItemAnimator Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler Adapter LayoutManager
16. Adapter • Create View and ViewHolder • Bind an item to a holder • Notify RecyclerView about changes • Notify data out of sync
17. Adapter • item interactions handling (clicks etc.) • multiple view types • recycler recovery (onFailedToRecycleView) • granular data change events
18. Adapter LayoutManager ItemAnimator Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler
19. Recycler • Manage scrapped or detached item views for reuse • A "scrapped" view is a view that is still attached to its parent RecyclerView but that has been marked for removal or reuse. Recycled View Pool
20. Recycler Recycled View Pool • Sanctuary for reserve ViewHolders • Can be shared between RecyclerViews or custom view groups RecyclerView.setRecycledViewPool(RecycledViewPool) • Per Activity context
21. Adapter LayoutManager ItemAnimator Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler RecyclerView
22. LayoutManager Adapter Recycled View Pool Recycler ViewHolder — Birth RecyclerView
23. LayoutManager Adapter Recycled View Pool Cache ViewHolder — Birth RecyclerView getViewForPosition getViewForPosition getViewType getViewHolderByType createViewHolder bindViewHolder
24. LayoutManager Adapter Recycled View Pool Cache RecyclerView addView onViewAttachedToWindow ViewHolder — Birth
25. LayoutManager Adapter Recycled View Pool Cache RecyclerView removeAndRecycleView onViewDetachedFromWindow ViewHolder — Reserve Is Valid? recycle
 (oldest cache) onViewRecycled
 (oldest cache)
26. ViewHolder — Reserve private void scrapOrRecycleView(Recycler recycler, int index, View view) { final ViewHolder viewHolder = getChildViewHolderInt(view); if (viewHolder.shouldIgnore()) { if (DEBUG) { Log.d(TAG, "ignoring view " + viewHolder); } return; } if (viewHolder.isInvalid() && !viewHolder.isRemoved() && !mRecyclerView.mAdapter.hasStableIds()) { removeViewAt(index); recycler.recycleViewHolderInternal(viewHolder); } else { detachViewAt(index); recycler.scrapView(view); mRecyclerView.mViewInfoStore.onViewDetached(viewHolder); } } Is Valid?
27. LayoutManager Adapter Recycled View Pool Cache RecyclerView ViewHolder — Fancy Reserve ItemAnimator
28. Recycler LayoutManager Adapter Recycled View Pool Scrap Heap RecyclerView onLayoutChildren ViewHolder — Fancy Reserve Re add to ViewGroup hide from LM for each disappearing child animate child onAnimationFinished onViewDetachedFromWindow cache or recycle ItemAnimator
29. LayoutManager Adapter Recycled View Pool RecyclerView removeAndRecycleView ViewHolder — Death Is Valid? Has transient state? onFailedToRecycle trust me!
30. Recycled View Pool RecyclerView ViewHolder — Death 2 Is there room for another VH type X? add view to pool Icon made by Freepik from Flaticon are licensed by CC 3.0 BY
31. ViewHolder — Death 2 Icon made by Freepik from Flaticon are licensed by CC 3.0 BY Why it didn’t cache? • Too many ViewHolders of the same type How come? • Animate cross fade for all views • notifyItemChanged(0, getItemCount)) How to fix? • Granular updates (notifyDataSetChanged(3)) • pool.setMaxRecycledViews(type, count)
32. Adapter LayoutManager ItemAnimator Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler RecyclerView
33. Adapter LayoutManager ItemAnimator Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler
34. Item Decorations • Can add offset to view bounds • Custom drawing on RecyclerView canvas • Can have multiple ItemDecoration
35. fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) Item Decorations
36. fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) Item Decorations
37. fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) Item Decorations
38. Item Decorations fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State)
39. fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) Item Decorations
40. fun onDraw(c: Canvas, parent: RecyclerView, state: RecyclerView.State) Item Decorations
41. Item Decorations fun onDrawOver(c: Canvas, parent: RecyclerView, state: RecyclerView.State)
42. Item Decorations • Do NOT try to access the adapter • Keep necessary information in View Holder • General onDraw rules apply (don’t allocate etc.) • recyclerView.getChildViewHolder(view)
43. Adapter LayoutManager ItemAnimator Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler
44. ItemAnimator https://youtu.be/imsr8NrIAMs
45. ItemAnimator Adapter LayoutManager Item Decorations Adapter Helper Recycled View Pool Recycler Child Helper
46. ItemAnimator Adapter LayoutManager Item Decorations Adapter Helper Recycled View Pool Recycler Child Helper
47. Child Helper View LayoutManager ItemAnimator
48. Child Helper Provide a virtual children list to the LayoutManager Brest Vitebsk Gomel Grodno Mogilev Minsk layoutManager.getChildAt(3) = recyclerView.getChildAt(3) = Grodno Mogilev Mogilev
49. Child Helper ItemAnimator Adapter LayoutManager Item Decorations Recycled View Pool Recycler Adapter Helper
50. Child Helper ItemAnimator Adapter LayoutManager Item Decorations Recycled View Pool Recycler Adapter Helper
51. Adapter Helper Brest Vitebsk Gomel Grodno Mogilev Minsk 25 26 27 28 29 30 ADD (25, 1) RM (31, 2) viewHolder.getAdapterPosition() position: 29 30 MV (28, 27)
52. Adapter Helper • Track ViewHolder positions • Virtual adapter for the Layout Manager
53. RecyclerView LayoutManager ItemAnimator Adapter Item Decorations Child Helper Adapter Helper Recycled View Pool Recycler
54. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY Tips & Tricks
55. No Update = no onBind Items are not rebound unless updated adapter.notifyItemMoved(2, 7) 0 onBind calls
56. onBind position != final position fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) { holder.itemView.setOnClickListener { removeAtPosition(position) } } BUG: onBindViewHolder(holder, 5) notifyItemMoved(5, 15) holder.itemView.callOnClick()
57. onBind position != final position fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) { holder.itemView.setOnClickListener { removeAtPosition(holder.adapterPosition) } }
58. Positions: Adapter vs Layout Brest Vitebsk Gomel Grodno Mogilev Minsk 0 1 2 3 4 5 0 1 2 3 4 5 AP LP move(2, 5) 0 1 5 2 3 4 0 1 2 3 4 5 AP LP onLayout
59. Positions: Adapter vs Layout Brest Vitebsk Grodno Mogilev Minsk Gomel 0 1 2 3 4 5 0 1 2 3 4 5 AP LP move(2, 5) 0 1 5 2 3 4 0 1 2 3 4 5 AP LP onLayout
60. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY Drag and Swipe ItemTouchHelper - supports both swipe and drag, together if you please - per ViewHolder val callback = SimpleItemTouchHelperCallback(adapter) val touchHelper = ItemTouchHelper(callback) touchHelper.attachToRecyclerView(recyclerView) https://medium.com/@ipaulpro/drag-and-swipe-with-recyclerview-b9456d2b1aaf
61. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY DiffUtil • calculates the difference between two given lists • O(N) space to find adds and removes • O(N + D^2) time • plus O(N^2) time to detect moves random UUID Strings, Nexus 5X with M: • 100 items and 10 modifications: avg: 0.39 ms, median: 0.35 ms • 100 items and 100 modifications: 3.82 ms, median: 3.75 ms • 100 items and 100 modifications without moves: 2.09 ms, median: 2.06 ms • 1000 items and 50 modifications: avg: 4.67 ms, median: 4.59 ms • 1000 items and 50 modifications without moves: avg: 3.59 ms, median: 3.50 ms • 1000 items and 200 modifications: 27.07 ms, median: 26.92 ms • 1000 items and 200 modifications without moves: 13.54 ms, median: 13.36 ms https://developer.android.com/reference/android/support/v7/util/DiffUtil.html
62. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY RecyclerView Prefetch https://medium.com/google-developers/recyclerview-prefetch-c2f269075710
63. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY RecyclerView Prefetch https://medium.com/google-developers/recyclerview-prefetch-c2f269075710
64. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY RecyclerView Prefetch https://medium.com/google-developers/recyclerview-prefetch-c2f269075710
65. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY RecyclerView Prefetch https://medium.com/google-developers/recyclerview-prefetch-c2f269075710
66. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY RecyclerView Prefetch https://medium.com/google-developers/recyclerview-prefetch-c2f269075710
67. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY PrecomputedText API in Android Pie https://medium.com/mindorks/precomputedtext-new-api-in-android-pie-74eb8f420ee6
68. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY Prefetch Text Layout in RecyclerView https://medium.com/androiddevelopers/prefetch-text-layout-in-recyclerview-4acf9103f438
69. Icons made by Freepik from Flaticon are licensed by CC 3.0 BY More info • RecyclerView ins and outs by Adam Powell & Yigit Boyar — https://youtu.be/LqBlYJTfLP4 • Pro RecyclerView by Yigit Boyar— https://youtu.be/KhLVD6iiZQs • Radical RecyclerView by Lisa Wray — https://youtu.be/TS_J0Qw4zl0 • 032. RecyclerView 13000 by Артур Василов — https://youtu.be/860_Y5TXh1Y
70. contact@vladds.com Icons made by Freepik from Flaticon are licensed by CC 3.0 BY
71. contact@vladds.com Icons made by Freepik from Flaticon are licensed by CC 3.0 BY https://vladds.com/recycler_view.pdf