text stringlengths 1 474 |
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assets is downloaded by the Flutter engine using the |
Play store’s delivery feature. |
<topic_end> |
<topic_start>Improving rendering performance |
info Note |
To learn how to use the Performance View |
(part of Flutter DevTools) |
for debugging performance issues, |
see Using the Performance view.Rendering animations in your app is one of the most cited |
topics of interest when it comes to measuring performance. |
Thanks in part to Flutter’s Skia engine and its ability |
to quickly create and dispose of widgets, |
Flutter applications are performant by default, |
so you only need to avoid common pitfalls to achieve |
excellent performance.<topic_end> |
<topic_start> |
General advice |
If you see janky (non-smooth) animations, make |
sure that you are profiling performance with an |
app built in profile mode. |
The default Flutter build creates an app in debug mode, |
which is not indicative of release performance. |
For information, |
see Flutter’s build modes.A couple common pitfalls:For more information on evaluating performance |
including information on common pitfalls, |
see the following docs:<topic_end> |
<topic_start> |
Mobile-only advice |
Do you see noticeable jank on your mobile app, but only on |
the first run of an animation? If so, see |
Reduce shader animation jank on mobile.<topic_end> |
<topic_start> |
Web-only advice |
The following series of articles cover what the Flutter Material |
team learned when improving performance of the Flutter Gallery |
app on the web: |
<topic_end> |
<topic_start>Flutter performance profiling |
info Note |
To learn how to use the Performance View |
(part of Flutter DevTools) |
for debugging performance issues, |
see Using the Performance view.<topic_end> |
<topic_start>What you'll learn |
It’s been said that “a fast app is great, |
but a smooth app is even better.” |
If your app isn’t rendering smoothly, |
how do you fix it? Where do you begin? |
This guide shows you where to start, |
steps to take, and tools that can help.info Note<topic_end> |
<topic_start> |
Diagnosing performance problems |
To diagnose an app with performance problems, you’ll enable |
the performance overlay to look at the UI and raster threads. |
Before you begin, make sure that you’re running in |
profile mode, and that you’re not using an emulator. |
For best results, you might choose the slowest device that |
your users might use.<topic_end> |
<topic_start> |
Connect to a physical device |
Almost all performance debugging for Flutter applications |
should be conducted on a physical Android or iOS device, |
with your Flutter application running in profile mode. |
Using debug mode, or running apps on simulators |
or emulators, is generally not indicative of the final |
behavior of release mode builds. |
You should consider checking performance |
on the slowest device that your users might reasonably use.<topic_end> |
<topic_start>Why you should run on a real device: |
<topic_end> |
<topic_start> |
Run in profile mode |
Flutter’s profile mode compiles and launches your application |
almost identically to release mode, but with just enough additional |
functionality to allow debugging performance problems. |
For example, profile mode provides tracing information to the |
profiling tools.info Note |
DevTools can’t connect to a Flutter web app running |
in profile mode. Use Chrome DevTools to |
generate timeline events for a web app.Launch the app in profile mode as follows:In VS Code, open your launch.json file, and set the |
flutterMode property to profile |
(when done profiling, change it back to release or debug):From the command line, use the --profile flag:For more information on the different modes, |
see Flutter’s build modes.You’ll begin by opening DevTools and viewing |
the performance overlay, as discussed in the next section.<topic_end> |
<topic_start> |
Launch DevTools |
DevTools provides features like profiling, examining the heap, |
displaying code coverage, enabling the performance overlay, |
and a step-by-step debugger. |
DevTools’ Timeline view allows you to investigate the |
UI performance of your application on a frame-by-frame basis.Once your app is running in profile mode, |
launch DevTools.<topic_end> |
<topic_start> |
The performance overlay |
The performance overlay displays statistics in two graphs |
that show where time is being spent in your app. If the UI |
is janky (skipping frames), these graphs help you figure out why. |
The graphs display on top of your running app, but they aren’t |
drawn like a normal widget—the Flutter engine itself |
paints the overlay and only minimally impacts performance. |
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