Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Layout Traversals (Droidcon Turin 2015)
Search
Lucas Rocha
April 10, 2015
16
590
Layout Traversals (Droidcon Turin 2015)
Presented at Droidcon Turin 2015
Lucas Rocha
April 10, 2015
Tweet
Share
More Decks by Lucas Rocha
See All by Lucas Rocha
Design-Engineering Workflow
lucasr
2
400
Layout Traversals (GDG Devfest 2014)
lucasr
9
520
Custom Layouts
lucasr
34
2k
Introducing Smoothie
lucasr
7
490
Bringing Firefox to Android
lucasr
6
530
A Million Times Pattrn
lucasr
6
420
Mozilla & Mobile
lucasr
2
180
The State of Firefox Mobile
lucasr
1
2.1k
Featured
See All Featured
Easily Structure & Communicate Ideas using Wireframe
afnizarnur
191
16k
The Art of Delivering Value - GDevCon NA Keynote
reverentgeek
7
150
Music & Morning Musume
bryan
46
6.1k
Making the Leap to Tech Lead
cromwellryan
132
8.9k
Building a Scalable Design System with Sketch
lauravandoore
459
33k
Testing 201, or: Great Expectations
jmmastey
38
7k
Become a Pro
speakerdeck
PRO
24
5k
RailsConf & Balkan Ruby 2019: The Past, Present, and Future of Rails at GitHub
eileencodes
131
33k
YesSQL, Process and Tooling at Scale
rocio
167
14k
Thoughts on Productivity
jonyablonski
67
4.3k
No one is an island. Learnings from fostering a developers community.
thoeni
19
3k
Gamification - CAS2011
davidbonilla
80
5k
Transcript
LAYOUT TRAVERSALS Droidcon Turin, 2015
LUCAS ROCHA +LucasRocha | @lucasratmundo
None
BE DELIBERATE Less handwavy UI code
THE BASICS From inside out.
UI TOOLKITS Layout + Rendering + Input Events
OLD SCHOOL Nested boxes, rudimentary motion API.
PRE-JELLY BEAN public final class ViewRoot extends Handler ... {
... public void scheduleTraversals() { if (!mTraversalScheduled) { mTraversalScheduled = true; sendEmptyMessage(DO_TRAVERSAL); } } ... public void handleMessage(Message msg) { ... case DO_TRAVERSAL: performTraversals(); ... } } ViewRoot.java
MODERNIZE Predictable notion of time that drives input, layout, and
motion.
TICK TOCK VSYNC sets the pace. No tearing, no extra
work.
CHOREOGRAPHER f1 f2 f3 f4 f5 . . . .
. . VSYNC (60fps) Resize view Redraw view Input Events
CHOREOGRAPHER public void onVsync(long timestampNanos, int builtInDisplayId, int frame) {
... scheduleVsync(); ... } ... void doFrame(long frameTimeNanos, int frame) { ... if (!mFrameScheduled) { return; } ... doCallbacks(Choreographer.CALLBACK_INPUT, frameTimeNanos); doCallbacks(Choreographer.CALLBACK_ANIMATION, frameTimeNanos); doCallbacks(Choreographer.CALLBACK_TRAVERSAL, frameTimeNanos); ... } Choreographer.java
ViewRootImpl Connects WindowManager with the View framework
THE ROOT * * SurfaceFlinger ViewRootImpl
VIEWS Measure + Layout + Draw
TRAVERSAL * performTraversals() f2 performTraversals()
MEASURE * measure(int, int) f2 M M M M M
M → onMeasure(int, int) measureHierarchy(...)
LAZY MEASURE Multi-MeasureSpec cache, invalidated in requestLayout()
LAZY MEASURE public final void measure(int widthMeasureSpec, int heightMeasureSpec) {
... int cacheIndex = mMeasureCache.indexOfKey(key); if (cacheIndex < 0 || sIgnoreMeasureCache) { onMeasure(widthMeasureSpec, heightMeasureSpec); mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT; } else { long value = mMeasureCache.valueAt(cacheIndex); setMeasuredDimensionRaw((int) (value >> 32), (int) value); mPrivateFlags3 |= PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT; } ... } View.java
LAZY MEASURE public void layout(int l, int t, int r,
int b) { if ((flags & PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT) != 0) { onMeasure(mOldWidthMeasureSpec, mOldHeightMeasureSpec); mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT; } ... } View.java
LAYOUT * f2 M L M L M L M
L M L M L layout(int, int, int, int) → onLayout(boolean, int, int, int, int) performLayout()
FRAME IT public void layout(int l, int t, int r,
int b) { ... boolean changed = isLayoutModeOptical(mParent) ? setOpticalFrame(l, t, r, b) : setFrame(l, t, r, b); ... } View.java
DRAW * f2 M L D M L D M
L D M L D M L D M L D draw(Canvas) → onDraw(Canvas) performDraw()
DISPLAY LISTS private DisplayList getDisplayList(...) { ... final HardwareCanvas canvas
= displayList.start(width, height); ... draw(canvas); ... displayList.end(); ... } View.java
INVARIANTS Layout means measurement is done. Drawing means layout is
done.
SMELLS 1. getMeasured*() calls outside onLayout() 2. New allocations during
traversal · onLayout: ok-ish · onMeasure: avoid · onDraw: nope 3. post(Runnable) to mean “after layout”
HAPPENS TO WORK public final class MyActivity extends Activity {
... @Override public void onCreate() { final View myView = findViewById(R.id.some_id); myView.post(new Runnable() { @Override public void run() { Log.d(“LOGTAG”, myView.getWidth()); } }); } ... }
LOOPER BARRIERS void scheduleTraversals() { ... mTraversalBarrier = mHandler.getLooper().postSyncBarrier(); ...
} ViewRootImpl.java
TREE OBSERVER Use OnPreDrawListener!
TRANSITIONS http://lucasr.org/?p=3902
OnPreDrawListener // 1. Save layout state and wait for next
frame. getViewTreeObserver().addOnPreDrawListener(new OnPreDrawListener() { @Override public boolean onPreDraw() { getViewTreeObserver().removeOnPreDrawListener(this); // 2. Restore original layout state. // 3. Trigger animators towards new layout state. } }
CHANGES Resize, redraw & animate.
* requestLayout() f1 f2 f3 f4 f5 . . .
. . .
requestLayout() public void requestLayout() { ... if (mParent != null
&& !mParent.isLayoutRequested()) { mParent.requestLayout(); } ... } void scheduleTraversals() { ... mChoreographer.postCallback( Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null); ... } View.java ViewRootImpl.java
* Invalidate(...) f1 f2 f3 f4 f5 . . .
. . .
invalidate(...) public void invalidateInternal(...) { ... mPrivateFlags |= PFLAG_INVALIDATED; ...
if (mParent != null && mAttachInfo != null && l < r && t < b) { final Rect damage = mAttachInfo.mTmpInvalRect; damage.set(l, t, r, b); mParent.invalidateChild(this, damage); } ... } boolean draw(...) { ... mRecreateDisplayList = (mPrivateFlags & PFLAG_INVALIDATED) == PFLAG_INVALIDATED; ... } View.java
* postOnAnimation() f1 f2 f3 f4 f5 . . .
. . . ValueAnimator ...
postOnAnimation() public void postOnAnimation(Runnable action) { ... attachInfo.mViewRootImpl.mChoreographer.postCallback( Choreographer.CALLBACK_ANIMATION, action,
null); ... } void doFrame(long frameTimeNanos, int frame) { ... doCallbacks(Choreographer.CALLBACK_INPUT, frameTimeNanos); doCallbacks(Choreographer.CALLBACK_ANIMATION, frameTimeNanos); doCallbacks(Choreographer.CALLBACK_TRAVERSAL, frameTimeNanos); ... } View.java Choreographer.java
BASIC TIPS 1. No layout requests during layout 2. No
layout requests during animations 3. Invalidate regions when possible
PERFORMANCE 1. Simplify your view hierarchy 2. Avoid multi-pass measurement
GO CUSTOM Simplify view hierarchy, performance, missing features. http://lucasr.org/?p=3920
PROBE IT! Intercept view methods. Dissect layout traversals. https://github.com/lucasr/probe
WRAP VIEW METHODS public class LogRequestLayout extends Interceptor { @Override
public void requestLayout(View view) { super.requestLayout(view); Log.d(LOGTAG, “requestLayout() on ” + view); } }
DEPLOY public final class MainActivity extends Activity { @Override protected
void onCreate(Bundle savedInstanceState) { Probe.deploy(this, new DrawGreen(), new Filter.ViewId(R.id.view2)); super.onCreate(savedInstanceState); setContentView(R.id.main_activity); } }
FANCY HACKING ON DEEP LAYOUT STUFF? We're hiring :-)
QUESTIONS? +LucasRocha | @lucasratmundo