Flutter Flutter Flashcards

24 sample cards from the Flutter deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Which widget is the primary tool for imperative navigation between screens in Flutter?

   The $\texttt{Navigator}$ widget, which manages a stack of Route objects.

2. How do you navigate to a new screen and how do you return from it?

   Use $\texttt{Navigator.push()}$ to add a route to the stack and $\texttt{Navigator.pop()}$ to remove the top route and return to the previous screen.

3. What is the difference between imperative and declarative navigation in Flutter?

   Imperative navigation uses push/pop calls on the Navigator; declarative navigation (Navigator 2.0 / Router API, e.g. go_router) derives the whole route stack from app state.

4. How do you define and use named routes in Flutter?

   Register a map in MaterialApp's $\texttt{routes:}$ property and navigate with $\texttt{Navigator.pushNamed(context, '/details')}$.

5. How do you pass data back to a previous screen when popping a route?

   Pass a value to $\texttt{Navigator.pop(context, result)}$; the awaited Future returned by the original push completes with that result.

6. Which widget groups form fields and manages their validation collectively?

   The $\texttt{Form}$ widget, coordinated via a $\texttt{GlobalKey<FormState>}$.

7. How do you trigger validation of all fields in a Form?

   Call $\texttt{formKey.currentState!.validate()}$, which runs each field's validator and returns true only if all pass.

8. What is the purpose of a TextEditingController?

   It reads and controls the current text of a TextField, allows programmatic changes, and notifies listeners as the user types.

9. What does a TextFormField's validator function return to indicate valid input?

   It returns $\texttt{null}$ for valid input, or a String error message to display when input is invalid.

10. Which package is commonly used to make HTTP requests in Flutter?

    The $\texttt{http}$ package (with Dio as a popular feature-rich alternative).

11. How does Dart handle asynchronous operations like network calls?

    With Futures and the async/await keywords; an async function returns a Future and await pauses execution until the Future completes.

12. Which widget rebuilds its UI based on the latest snapshot of a Future or Stream?

    $\texttt{FutureBuilder}$ (for a Future) and $\texttt{StreamBuilder}$ (for a Stream).

13. How do you convert a JSON string into Dart objects?

    Use $\texttt{jsonDecode()}$ from dart:convert to get a Map, then map it to a model (often via a fromJson factory constructor).

14. Which lightweight package stores simple key-value data persistently on the device?

    $\texttt{shared\_preferences}$, ideal for small primitives like settings and flags.

15. Name two options for structured local database storage in Flutter.

    SQLite (via the $\texttt{sqflite}$ package) and NoSQL stores like Hive or Isar.

16. Which widget drives an animation by continuously producing values between two bounds?

    An $\texttt{AnimationController}$, typically paired with a Tween and a vsync TickerProvider.

17. What is the role of a Tween in Flutter animations?

    A Tween defines the start and end values of a property and interpolates ('in-betweens') the intermediate values as the animation progresses from 0.0 to 1.0.

18. How do you build a fully custom widget in Flutter?

    By composing existing widgets in a StatelessWidget/StatefulWidget subclass, or for full control over layout and painting, by using CustomPainter or subclassing RenderObject.

19. Which optimizations improve Flutter app performance and reduce unnecessary rebuilds?

    Use const constructors, keep build methods small, use ListView.builder for long lists, add RepaintBoundary to isolate repaints, and avoid rebuilding expensive subtrees.

20. What are the three main levels of testing in Flutter?

    Unit tests (individual functions/classes), Widget tests (a single widget in isolation), and Integration tests (the full app end-to-end).

21. Which command builds a release Android App Bundle for the Play Store?

    $\texttt{flutter build appbundle}$ (use $\texttt{flutter build ios}$ for iOS release builds).

22. Where are third-party Flutter packages and plugins declared, and where are they published?

    They are declared under $\texttt{dependencies:}$ in the pubspec.yaml file and published on pub.dev.

23. What is the difference between a Flutter 'package' and a 'plugin'?

    A package contains pure Dart code; a plugin additionally includes platform-specific native code (via platform channels) to access device APIs like the camera or GPS.

24. What are the main rendering strategies available for Flutter web?

    The HTML/CanvasKit renderers historically, with newer builds using CanvasKit (Skia via WebAssembly) or the Skwasm/Impeller path for consistent, high-fidelity rendering in the browser.

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