So far you’ve been running your app in debug mode. Debug
mode trades performance for useful developer features such
as hot reload and step debugging. It’s not unexpected to
see slow performance and janky animations in debug mode.
Once you are ready to analyze performance or release your
app, you’ll want to use Flutter’s “profile” or “release”
build modes. For more details, see Flutter’s build modes.

Important:
  If you’re concerned about the package size of your app,
  see Measuring your app’s size.

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