IntelliJ IDEA 2020.3.1中Flutter与Java代码自动补全（Intellisense）功能失效求助

Hey there, sorry to hear IntelliJ's code completion has suddenly stopped working on your Java/Flutter projects—let's walk through some less common fixes that might get it back up and running:

• Check for plugin conflicts
  Third-party plugins are a frequent culprit here. Head to Settings/Preferences > Plugins, disable all non-built-in plugins, then restart IDEA. If Intellisense starts working again, re-enable plugins one by one to pinpoint the problematic one. Note that some newer Flutter plugins might not be fully compatible with the 2020.3.1 IDE version—double-check plugin compatibility with your IDE release.

• Verify module dependency configuration
  Corrupted module settings can break code recognition. Go to File > Project Structure > Modules, select each of your project modules, and check the Dependencies tab:

  • Ensure the correct JDK is listed for Java modules
  • For Flutter modules, confirm the Flutter SDK path is properly linked and no dependencies are marked as missing
    If anything looks off, re-add the SDKs or refresh dependencies.

• Re-import your project
  Sometimes IDE-generated config files (like .iml files) get corrupted. Remove the project from IDEA (don't delete local files!), then re-import it by selecting the project root and choosing the correct project type (Java/Flutter). Let IDEA rebuild all configuration files from scratch.

• Double-check code completion settings
  It's easy to accidentally tweak these without noticing. Go to Settings/Preferences > Editor > General > Code Completion:

  • Make sure Autopopup code completion is checked
  • Ensure options like Show suggestions as you type and Insert selected suggestion by pressing space, dot, etc. are enabled
    Also, check Settings/Preferences > Editor > Inspections to confirm you haven't disabled critical code inspections—Intellisense relies on these to generate accurate suggestions.

• Clear IDE system cache (not just Invalidate Caches)
  The "Invalidate Caches/Restart" doesn't always clear all system-level cache. Close IDEA entirely, then delete the system cache directory for your IDE version:

  • Windows: C:\Users\<YourUsername>\.IntelliJIdea2020.3\system
  • Mac: ~/Library/Caches/JetBrains/IntelliJIdea2020.3
  • Linux: ~/.cache/JetBrains/IntelliJIdea2020.3
    Restart IDEA afterward—it will rebuild the cache from scratch.

• Refresh Flutter pub dependencies
  For Flutter projects, incomplete or corrupted pub dependencies can break Intellisense. Open a terminal in your project root, run flutter pub get, and fix any errors that pop up. Restart IDEA once the command completes successfully.

内容的提问来源于stack exchange，提问作者Pain