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the flutter framework emits timeline events as it works to build frames,
draw scenes, and track other activity such as HTTP request timings
and garbage collection. these events show up here in the timeline.
you can also send your own timeline events using the dart:developer
timeline and TimelineTask APIs.
for help with navigating and using the trace viewer,
click the ? button at the top right of the timeline
events tab bar. to refresh the timeline with new events from
your application, click the refresh button
(also in the upper right corner of the tab controls).
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advanced debugging tools
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enhance tracing
to view more detailed tracing in the timeline events chart,
use the options in the enhance tracing dropdown:
info note
frame times might be negatively affected when these options are enabled.
to see the new timeline events, reproduce the activity
in your app that you are interested in tracing,
and then select a frame to inspect the timeline.
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track widget builds
to see the build() method events in the timeline,
enable the track widget builds option.
the name of the widget is shown in the timeline event.
watch this video for an example of tracking widget builds
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track layouts
to see render object layout events in the timeline,
enable the track layouts option:
watch this video for an example of tracking layouts
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track paints
to see render object paint events in the timeline,
enable the track paints option:
watch this video for an example of tracking paints
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more debugging options
to diagnose performance problems related to rendering layers,
toggle off a rendering layer.
these options are enabled by default.
to see the effects on your app’s performance,
reproduce the activity in your app.
then select the new frames in the frames chart
to inspect the timeline events
with the layers disabled.
if raster time has significantly decreased,
excessive use of the effects you disabled might be contributing
to the jank you saw in your app.
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import and export
DevTools supports importing and exporting performance snapshots.
clicking the export button (upper-right corner above the
frame rendering chart) downloads a snapshot of the current data on the
performance page. to import a performance snapshot, you can drag and drop the
snapshot into DevTools from any page. note that DevTools only
supports importing files that were originally exported from DevTools.
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other resources
to learn how to monitor an app’s performance and
detect jank using DevTools, check out a guided
performance view tutorial.
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using the CPU profiler view
info note
the CPU profiler view works with dart CLI and mobile apps only.
use chrome DevTools to analyze performance
of a web app.
the CPU profiler view allows you to record and profile a
session from your dart or flutter application.
the profiler can help you solve performance problems
or generally understand your app’s CPU activity.
the dart VM collects CPU samples
(a snapshot of the CPU call stack at a single point in time)
and sends the data to DevTools for visualization.
by aggregating many CPU samples together,
the profiler can help you understand where the CPU
spends most of its time.
info note
if you are running a flutter application,
use a profile build to analyze performance.
CPU profiles are not indicative of release performance
unless your flutter application is run in profile mode.
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CPU profiler
start recording a CPU profile by clicking record.
when you are done recording, click stop. at this point,
CPU profiling data is pulled from the VM and displayed
in the profiler views (call tree, bottom up, method table,