How to autocomplete/import Flutter classes in IntelliJ?
This is a known issue.
For performance reasons the DartAnalyzer was built to only load libraries that were imported anywhere in the projects code already. The overall performance of DartAnalyzer was improved a lot since then and it would now allow to provide better suggestions, but it seems there weren’t enough resources available yet to get it implemented.
Upvote and follow https://github.com/dart-lang/sdk/issues/25820
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