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Kickstart Modern Android Development with Jetpack and Kotlin

You're reading from   Kickstart Modern Android Development with Jetpack and Kotlin Enhance your applications by integrating Jetpack and applying modern app architectural concepts

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Product type Paperback
Published in May 2022
Publisher Packt
ISBN-13 9781801811071
Length 472 pages
Edition 1st Edition
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Catalin Ghita Catalin Ghita
Author Profile Icon Catalin Ghita
Catalin Ghita
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Table of Contents (17) Chapters Close

Preface 1. Part 1: Exploring the Core Jetpack Suite and Other Libraries
2. Chapter 1: Creating a Modern UI with Jetpack Compose FREE CHAPTER 3. Chapter 2: Handling UI State with Jetpack ViewModel 4. Chapter 3: Displaying Data from REST APIs with Retrofit 5. Chapter 4: Handling Async Operations with Coroutines 6. Chapter 5: Adding Navigation in Compose With Jetpack Navigation 7. Part 2: A Guide to Clean Application Architecture with Jetpack Libraries
8. Chapter 6: Adding Offline Capabilities with Jetpack Room 9. Chapter 7: Introducing Presentation Patterns in Android 10. Chapter 8: Getting Started with Clean Architecture in Android 11. Chapter 9: Implementing Dependency Injection with Jetpack Hilt 12. Chapter 10: Test Your App with UI and Unit Tests 13. Part 3: Diving into Other Jetpack Libraries
14. Chapter 11: Creating Infinite Lists with Jetpack Paging and Kotlin Flow 15. Chapter 12: Exploring the Jetpack Lifecycle Components 16. Other Books You May Enjoy

Making our countdown component aware of the lifecycle of composables

The main issue is that our CustomCountdown component still runs its countdown even after the CountdownItem() composable leaves composition. We want to pause the timer when its corresponding composable is not visible anymore. With such an approach, we can prevent users from cheating, and we can award the prize only to users that have had the countdown timer visible for the full amount of time. Basically, if the timer is not visible anymore, the countdown should stop.

To pause the timer when its corresponding composable function leaves composition, we must somehow call the stop() function exposed by CustomCountdown. But when should we do that?

If you look inside the body of the CountdownItem() composable, you will notice that we have already registered a DisposableEffect() composable that notifies us when the CountdownItem() composable leaves composition by exposing the onDispose() callback:

@Composable
private...
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