Tale of a Smooth RecyclerView

Tips and tricks how to make you lists perform well

Transcript

2. The Tale of a Smooth RecyclerView ADAM ŠIMEK
3. Knowing how to code lists is important
10. Kulman’s test
13. But why?
14. ¯\_(ツ)_/¯
16. 16ms
17. “Well, that’s: user input, networking, data processing, database/disk I/O, view inflation, layout, drawing,… Thwre also other applications, cpus are slow, memories are too, everything takes forever. And then you are supposed to save battery.”
18. 16ms?
19. Let’s get started
20. ListView
21. ListView
22. RecyclerView
23. RecyclerView Architecture
24. ViewHolder
25. ViewHolder Best practice from ListView Lightweight view wrapper for list items Recycler holds a limited amount of them and reuses them One ViewHolder is used for more items (not at a time) It has it’s own lifecyle
26. ViewHolder Lifecycle @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {} @Override public void onBindViewHolder(ViewHolder holder, int position) {} @Override public void onViewAttachedToWindow(ViewHolder holder) {} @Override public void onViewDetachedFromWindow(ViewHolder holder) {} @Override public void onViewRecycled(ViewHolder holder) {} @Override public boolean onFailedToRecycleView(ViewHolder holder) {}
27. ViewHolder Lifecycle @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {} @Override public void onBindViewHolder(ViewHolder holder, int position) {} @Override public void onViewAttachedToWindow(ViewHolder holder) {} @Override public void onViewDetachedFromWindow(ViewHolder holder) {} @Override public void onViewRecycled(ViewHolder holder) {} @Override public boolean onFailedToRecycleView(ViewHolder holder) {}
28. “The fastest code is the code that never runs.” Sokrates
29. What not to do? Disk I/O - SQLite, SharedPreferences, Content Providers for (Comment comment : item.getComments()) {} Parsing of text, JSONu,…, complicated formatting,.. Html.fromHtml() Complicated layouts “I can go home, it’s runs smooth on my phone.” Critical code can be hidden (deep) in the abstraction
30. What to do? Everything expensive has to run in background …,or it has to be preprocessed You don’t have to show it right away → use tmp placeholders void onScrollStateChanged(…, int newState) mHandler.postDelayed(deferredBind, DELAY } ☝ it’s crucial to keep this balanced Test on various devices (low-end, tablets) …and with various data StrictMode
31. Recycling saves our planet. Turns out it can save your app too.
33. Guess what’s wrong? //ViewHolder code called in onBindViewHolder() @Override public void bindData(Object data, final int position) { mImageView.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { mClickHandler.onItemClicked(v, position, photo); } }); }
34. Guess what’s wrong? //ViewHolder code called in onBindViewHolder() @Override public void bindData(Object data, final int position) { mImageView.setOnClickListener(mClickListener); // use member var instead }
35. Guess what’s wrong? //ViewHolder code called in onBindViewHolder() @Override public void bindData(Object data, final int position, ItemClickListener listener) { mImageView.setOnClickListener(listener); // even better.. }
36. Guess what’s wrong? //ViewHolder code called in onBindViewHolder() @Override public void bindData(Object data, final int position) { mImageView.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { mClickHandler.onItemClicked(v, position, photo); } }); }
37. Guess what’s wrong? //ViewHolder code called in onBindViewHolder() @Override public void bindData(Object data, final int position) { mImageView.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { mClickHandler.onItemClicked(v, getAdapterPosition(), photo); } }); }
38. Measure twice, cut once.
39. AsyncTask
40. AsyncTask Runs tasks in serial → super slow Hm… executeOnExecutor(THREAD_POOL_EXECUTOR); Big operational overhead Tricky and unreliable task cancelling
41. java.util.concurrent.RejectedExecutionException: Task android.os.AsyncTask$3@36e83ee rejected from java.util.concurrent.ThreadPoolExecutor@a54e08f[Running, pool size = 13, active threads = 13, queued tasks = 128, completed tasks = 1055]
42. DIY Custom “taskmanager” … mDecodeThreadPool = new ThreadPoolExecutor( NUMBER_OF_CORES, // Initial pool size NUMBER_OF_CORES, // Max pool size KEEP_ALIVE_TIME, KEEP_ALIVE_TIME_UNIT, mDecodeWorkQueue); // 128 size in AsyncTask … mDecodeThreadPool.execute(DownloadTask); // execute task …
43. Sneaky things
44. Sneaky things View.requestLayout() ——————— RecyclerView.setHasFixedSize( boolean hasFixedSize ) ——————— TextView.setAllCaps(boolean allCaps) ——————— notifyDatasetChanged()
45. View.requestLayout()
46. View.requestLayout() + hasFixedSize void triggerUpdateProcessor() { if (POST_UPDATES_ON_ANIMATION && mHasFixedSize && mIsAttached) { ViewCompat.postOnAnimation(RecyclerView.this, mUpdateChildViewsRunnable); } else { mAdapterUpdateDuringMeasure = true; requestLayout(); } }
47. Sneaky things View.requestLayout() ——————— RecyclerView.setHasFixedSize( boolean hasFixedSize ) ——————— TextView.setAllCaps(boolean allCaps) ——————— notifyDatasetChanged()
48. TextView.setAllCaps() public void setAllCaps(boolean allCaps) { if (allCaps) { setTransformationMethod(new AllCapsTransformationMethod(getContext())); } else { setTransformationMethod(null); } }
49. Sneaky things View.requestLayout() ——————— RecyclerView.setHasFixedSize( boolean hasFixedSize ) ——————— TextView.setAllCaps(boolean allCaps) ——————— notifyDatasetChanged()
50. “Today I will do what others won't, so tomorrow I can accomplish what others can’t"
51. Prefetch
52. Systrace
53. Systrace - missed frame
54. Prefetch OFF
55. Prefetch ON
56. Prefetch Create and bind “up front” Estimates how long it will run to make sure it won’t cause delays Lollipop+ (RenderThread), support lib 25.1 setItemPrefetchEnabled(true) Supported by built-in LayoutManageres (API for custom ones) Watch out for onBindViewHolder - no animations,… setInitialPrefetchItemCount(N) You can see the difference with your naked eye
57. Thank you! @simekadam strava.com/athletes/simekadam
58. @simekadam strava.com/athletes/simekadam