# Application Lifecycle (Flutter)

> AppLifecycleState, WidgetsBindingObserver, background/foreground, app termination

- 20 interview questions
- Junior
- [Interview Questions: Flutter](https://sharpskill.dev/en/technologies/flutter/interview-questions.md)

## 1. Which mixin should be used to observe Flutter app lifecycle state changes?

**Answer**

WidgetsBindingObserver is Flutter's official mixin for observing app lifecycle state changes. It needs to be added to the State class and the observer registered with WidgetsBinding.instance.addObserver in initState, then removed in dispose.

## 2. Which WidgetsBindingObserver method is called when the app lifecycle state changes?

**Answer**

The didChangeAppLifecycleState method is called whenever the app lifecycle state changes. It receives an AppLifecycleState parameter indicating the new state of the application (resumed, inactive, paused, detached, hidden).

## 3. Which AppLifecycleState indicates the app is visible and responding to user input?

**Answer**

The resumed state indicates the app is visible, in the foreground, and responding to user input. This is the normal operating state where the user is actively interacting with the application.

## 17 more questions available

- When does AppLifecycleState.inactive occur on iOS?
- Which AppLifecycleState indicates the app is no longer visible to the user?

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