Interview Preparation
Flutter Interview Questions & Answers (2026)
Prepare for Flutter developer interviews with curated questions, explanations, code examples, and best practices.
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What is Flutter?
Flutter is Google's open-source UI toolkit for building natively compiled apps for mobile, web, and desktop from a single Dart codebase.
What is the difference between StatelessWidget and StatefulWidget?
A StatelessWidget is immutable and rebuilds only when its parent rebuilds; a StatefulWidget holds mutable state via a separate State object and can rebuild itself whenever that state changes.
Explain the widget lifecycle in Flutter.
A StatefulWidget's State goes through createState → initState → didChangeDependencies → build (repeated) → didUpdateWidget (on parent rebuild) → deactivate → dispose.
Describe Flutter's architecture — how does a widget end up as pixels on screen?
Flutter has three parallel trees — Widget, Element, and RenderObject — where widgets are immutable configuration, elements are the mutable instances that manage the tree, and render objects handle layout, painting, and hit-testing.
What is null safety in Dart?
Sound null safety means the compiler distinguishes nullable (`String?`) from non-nullable (`String`) types and guarantees, at compile time, that a non-nullable variable can never hold null.
What is the difference between Future and Stream in Dart?
A Future represents a single asynchronous value that completes once; a Stream represents a sequence of asynchronous values delivered over time, and can emit zero, one, or many events.
How does async/await work in Dart?
`async` marks a function as returning a Future and lets you use `await` inside it; `await` pauses execution of that function (without blocking the thread) until the awaited Future completes.
What are extension methods in Dart?
Extension methods let you add new functionality to an existing type — including types you don't own, like String or int — without modifying its source or subclassing it.
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