Meaning of Choreographer messages in Logcat

Question

I installed the latest versions of SDK  API 16  and got the latest ADT  I m now seeing these messages in the logcat  that I m quite sure  I haven t seen before  Does anyone have an idea about this      06-29 23 11 17 796  I Choreographer 691   Skipped 647 frames   The   application may be doing too much work on its main thread    I did a search and found this link  http   developer android com reference android view Choreographer html  This is a new class introduced in API 16   I need to know how I can determine what  too much work  my application may be doing as all my processing is done in AsyncTasks

User · Answer

I m late to the party  but hopefully this is a useful addition to the other answers here     Answering the Question   tl dr      I need to know how I can determine what  too much work  my application may be doing as all my processing is done in AsyncTasks    The following are all candidates    IO or expensive processing on the main thread  loading drawables  inflating layouts  and setting Uri s on ImageView s all constitute IO on the main thread  Rendering large complex deep View hierarchies Invalidating large portions of a View hierarchy Expensive onDraw methods in custom View s Expensive calculations in animations Running  worker  threads at too high a priority to be considered  background   AsyncTask s are  background  by default  java lang Thread is not  Generating lots of garbage  causing the garbage collector to  stop the world  - including the main thread - while it cleans up   To actually determine the specific cause you ll  need to profile your app   More Detail  I ve been trying to understand Choreographer by experimenting and looking at the code   The documentation of Choreographer opens with  Coordinates the timing of animations  input and drawing   which is actually a good description  but the rest goes on to over-emphasize animations    The Choreographer is actually responsible for executing 3 types of callbacks  which run in this order    input-handling callbacks  handling user-input such as touch events  animation callbacks for tweening between frames  supplying a stable frame-start-time to any all animations that are running  Running these callbacks 2nd means any animation-related calculations  e g  changing positions of View s  have already been made by the time the third type of callback is invoked    view traversal callbacks for drawing the view hierarchy    The aim is to match the rate at which invalidated views are re-drawn  and animations tweened  with the screen vsync - typically 60fps   The warning about skipped frames looks like an afterthought  The message is logged if a single pass through the 3 steps takes more than 30x the expected frame duration  so the smallest number you can expect to see in the log messages is  skipped 30 frames   If each pass takes 50  longer than it should you will still skip 30 frames  naughty   but you won t be warned about it   From the 3 steps involved its clear that it isn t only animations that can trigger the warning  Invalidating a significant portion of a large View hierarchy or a View with a complicated onDraw method might be enough   For example this will trigger the warning repeatedly   public class AnnoyTheChoreographerActivity extends Activity         Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState            setContentView R layout simple linear layout            ViewGroup root    ViewGroup  findViewById R id root            root addView new TextView this                Override             protected void onDraw Canvas canvas                    super onDraw canvas                   long sleep    long  Math random     1000L                   setText      sleep                   try                       Thread sleep sleep                     catch  Exception exc                                             which produces logging like this   11-06 09 35 15 865  13721-13721 example I Choreographer  Skipped 42 frames   The application may be doing too much work on its main thread  11-06 09 35 17 395  13721-13721 example I Choreographer  Skipped 59 frames   The application may be doing too much work on its main thread  11-06 09 35 18 030  13721-13721 example I Choreographer  Skipped 37 frames   The application may be doing too much work on its main thread    You can see from the stack during onDraw that the choreographer is involved regardless of whether you are animating      at example AnnoyTheChoreographerActivity 1 onDraw AnnoyTheChoreographerActivity java 25    at android view View draw View java 13759            quite a bit of repetition          at android view ViewGroup drawChild ViewGroup java 3169    at android view ViewGroup dispatchDraw ViewGroup java 3039    at android view View draw View java 13762    at android widget FrameLayout draw FrameLayout java 467    at com android internal policy impl PhoneWindow DecorView draw PhoneWindow java 2396    at android view View getDisplayList View java 12710    at android view View getDisplayList View java 12754    at android view HardwareRenderer GlRenderer draw HardwareRenderer java 1144    at android view ViewRootImpl draw ViewRootImpl java 2273    at android view ViewRootImpl performDraw ViewRootImpl java 2145    at android view ViewRootImpl performTraversals ViewRootImpl java 1956    at android view ViewRootImpl doTraversal ViewRootImpl java 1112    at android view ViewRootImpl TraversalRunnable run ViewRootImpl java 4472    at android view Choreographer CallbackRecord run Choreographer java 725    at android view Choreographer doCallbacks Choreographer java 555    at android view Choreographer doFrame Choreographer java 525    at android view Choreographer FrameDisplayEventReceiver run Choreographer java 711    at android os Handler handleCallback Handler java 615    at android os Handler dispatchMessage Handler java 92    at android os Looper loop Looper java 137    at android app ActivityThread main ActivityThread java 4898    Finally  if there is contention from other threads that reduce the amount of work the main thread can get done  the chance of skipping frames increases dramatically even though you aren t actually doing the work on the main thread    In this situation it might be considered misleading to suggest that the app is doing too much on the main thread  but Android really wants worker threads to run at low priority so that they are prevented from starving the main thread  If your worker threads are low priority the only way to trigger the Choreographer warning really is to do too much on the main thread

User · Answer

This if an Info message that could pop in your LogCat on many situations   In my case  it happened when I was inflating several views from XML layout files  programmatically  The message is harmless by itself  but could be the sign of a later problem that would use all the RAM your App is allowed to use and cause the mega-evil Force Close to happen  I have grown to be the kind of Developer that likes to see his Log WARN INFO ERROR Free      So  this is my own experience   I got the message   10-09 01 25 08 373  I Choreographer 11134   Skipped XXX frames   The application may be doing too much work on its main thread        when I was creating my own custom  super-complex multi-section list  by inflating a view from XML and populating its fields  images  text  etc     with the data coming from the response of a REST JSON web service  without paging capabilities  this views would act as rows  sub-section headers and section headers by adding all of them in the correct order to a LinearLayout  with vertical orientation inside a ScrollView   All of that to simulate a listView with clickable elements    but well  that s for another question   As a responsible Developer you want to make the App really efficient with the system resources  so the best practice for lists  when your lists are not so complex  is to use a ListActivity or ListFragment with a Loader and fill the ListView with an Adapter  this is supposedly more efficient  in fact it is and you should do it all the time  again    if your list is not so complex   Solution  I implemented paging on my REST JSON web service to prevent  big response sizes  and I wrapped the code that added the  rows    section headers  and  sub-section headers  views on an AsyncTask to keep the Main Thread cool   So    I hope my experience helps someone else that is cracking their heads open with this Info message   Happy hacking

User · Answer

This usually happens when debugging using the emulator  which is known to be slow anyway

User · Answer

In my case I have these messages when I show the sherlock action bar inderterminate progressbar  Since its not my library  I decided to hide the Choreographer outputs   You can hide the Choreographer outputs onto the Logcat view  using this filter expression    tag      Choreographer       I used a regex explained elsewhere    Regular expression to match a line that doesn  39 t contain a word

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Choreographer lets apps to connect themselves to the vsync  and properly time things to improve performance  Android view animations internally uses Choreographer for the same purpose  to properly time the animations and possibly improve performance  Since Choreographer is told about every vsync events  it can tell if one of the Runnables passed along by the Choreographer post  apis doesn t finish in one frame s time  causing frames to be skipped  In my understanding Choreographer can only detect the frame skipping  It has no way of telling why this happens  The message  quot The application may be doing too much work on its main thread  quot  could be misleading

[android] Meaning of Choreographer messages in Logcat

Answering the Question / tl:dr;

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