🚀 Flutter Basic Interview Questions – Simple Explanation

If you’re preparing for a Flutter interview, these are the most commonly asked basic questions with clear answers 👇

🔹 1. What is Flutter and why is it used?

Flutter is an open-source UI toolkit by Google used to build cross-platform apps using a single codebase.

Why Flutter?

• Faster development
• Beautiful and flexible UI
• Near-native performance
• One codebase for Android & iOS

🔹 2. Difference between Native, Flutter, and React Native

• Native Apps – Separate codebases for Android (Kotlin/Java) and iOS (Swift/Obj-C), best performance, direct access to platform APIs

• Flutter – Single codebase using Dart, uses its own rendering engine, performance is very close to native

• React Native – Uses JavaScript, UI components are mapped to native components via a bridge, which can be slightly slower compared to Flutter

🔹 3. Flutter Architecture (Simple)

Flutter has a layered architecture:

• Flutter framework - widgets, UI logic written in Dart
• Engine - handles rendering ui (converts widgets to pixels)
• Embedder (platform specific layer) - connect the engine to OS (android, ios, desktop), bridge between OS and Engine.

🔹 4. What is a Widget? Stateless vs Stateful

👉 In Flutter, everything is a widget.

A widget is the basic building block of Flutter UI.

Stateless Widget

• UI does not change
• No state Example: Text, Icon

Stateful Widget

• UI changes based on data
• Uses setState() Example: Counter, form, API data screen

👉 If the UI updates, use Stateful Widget.

🔹 5. Hot Reload vs Hot Restart

Hot Reload updates UI instantly and keeps the app state.

Hot Restart restarts the app and state is lost.

👉 Hot Reload is mainly used during UI development.

🔹 6. App Lifecycle & Widget Lifecycle

App Lifecycle

• resumed → app in foreground
• inactive → app visible but not active
• paused → app in background
• detached → app removed

Used to manage API calls, animations, and app state.

Flutter Widget or StatefulWidget lifecycle in order:

1. createState() → Creates the State object for the widget
2. initState() → Called once when the state is initialized; used for setup or API calls
3. didChangeDependencies() → Called after initState() and when InheritedWidgets change.
4. build() → Builds the UI; called after initState(), didChangeDependencies(), and on setState()
5. didUpdateWidget(oldWidget) → Called when parent widget data updates and passes new properties
6. setState() → Updates the UI when state changes
7. deactivate() → Called when the widget is removed from the tree temporarily
8. dispose() → Cleans up controllers, listeners, and memory when widget is permanently removed

💡 Interview Tip Explain concepts in simple words with real examples — interviewers value clarity more than definitions.