All 7 Local Data Storage with SharedPreferences questions
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How do you actually properly read and write different basic primitive data types, such as a String, an int, and a bool, using the shared_preferences package's own available methods? How can you properly store a genuinely more complex object, such as a List of strings or a Map, using SharedPreferences, given that it only genuinely natively supports fairly simple basic primitive types directly? How does SharedPreferences actually genuinely work differently underneath on Android compared to iOS, in terms of exactly what genuine underlying native storage mechanism each platform actually respectively uses? Why should genuinely sensitive data, such as an authentication token or a password, never actually be stored using regular SharedPreferences, and what should genuinely be used instead? How can you properly and safely migrate existing data already stored using SharedPreferences over to a genuinely more full featured local database such as Hive, once an app's own particular storage needs have genuinely grown beyond what simple key value storage alone can reasonably handle? What are the practical performance considerations of reading from SharedPreferences repeatedly throughout your app, and how does properly caching those particular values in memory help meaningfully avoid genuinely unnecessary repeated disk access?
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What is the shared_preferences package, and what kinds of genuinely simple data is it actually genuinely well suited for storing directly on a user's own device?

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Answer

The shared_preferences package provides a genuinely simple key value storage mechanism specifically for persisting small pieces of primitive data, such as strings, booleans, integers, and doubles, directly on a user's own device across separate individual app sessions, and it is genuinely best suited for storing simple app settings and preferences, such as a user's chosen theme, whether they have already seen a particular onboarding screen, or their preferred notification setting, rather than genuinely large amounts of structured data, which would generally be considerably better handled instead by a proper genuine database such as Hive or SQLite.
final prefs = await SharedPreferences.getInstance();
await prefs.setBool('hasSeenOnboarding', true);
final hasSeenOnboarding = prefs.getBool('hasSeenOnboarding') ?? false;
Real-world example An app properly remembers whether a user has already genuinely seen its own initial onboarding screens using SharedPreferences, correctly avoiding showing that same onboarding flow again every single time that particular user actually reopens the app.

Common follow-ups: What genuinely happens to data stored using SharedPreferences if a user actually uninstalls the app?;What is the specific practical difference between SharedPreferences and Hive in terms of exactly what kind of data each one is genuinely best suited for?

Hive & NoSQL Local Storage;App Theming & Dark Mode
All 7 Local Data Storage with SharedPreferences questions