Migrate Jetsnack to Navigation 3

[dturner]

I have migrated Jetsnack to use Navigation 3.

Previously Jetsnack was using nested NavHosts. The outer NavHost held the Home and SnackDetail destinations and the Home destination had a NavHost containing the Feed, Search, Cart and Profile destinations. The Home destinations were all wrapped with a scaffold that displayed the bottom navigation bar. The SnackDetail destination was full screen without the bottom navigation bar.

I have refactored this to use a single back stack and a single NavDisplay is used for all screens. This simplifies the code, but does introduce a caveat.

In order to display the bottom navigation bar on the Home destinations the NavDisplay is wrapped with the scaffold. This means that the bottom bar is conditionally hidden when the SnackDetail navigation key is the last item in the back stack. This isn't particularly scalable. This may be better implemented as a scene decorator, although we're still figuring out best practices there.

Still to do:

• When the moving between the Feed and Cart destinations the top bar disappears and reappears. It should stay put since it appears on both screens.
• Shared element transitions between Cart and SnackDetail seem to be broken
• Implement deeplinks.

Consider re-implementing this with nested NavDisplays.

[gemini-code-assist]

Summary of Changes

Hello @dturner, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request undertakes a significant refactoring of the Jetsnack application's navigation system by upgrading to Navigation 3. The core change involves transitioning from a complex nested NavHost setup to a more unified single back stack approach utilizing NavDisplay. This aims to simplify the overall navigation logic and state management, requiring adjustments to how UI elements, such as the bottom navigation bar, interact with the new navigation context.

Highlights

• Navigation Framework Upgrade: The application has been migrated from the older Navigation Compose library to the new Navigation 3 framework.
• Simplified Navigation Architecture: The previous architecture using nested NavHosts has been refactored to a single back stack managed by NavDisplay, streamlining navigation flow.
• Type-Safe Navigation Keys: New NavKey data objects have been introduced for defining navigation destinations, enhancing type safety and clarity across the application.
• Conditional Bottom Navigation Bar: The bottom navigation bar now conditionally hides when navigating to the SnackDetail screen, adapting to the single back stack model.

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Changelog

• Jetsnack/app/build.gradle.kts
  • Added Kotlin serialization plugin.
  • Removed androidx.navigation.compose dependency.
  • Added androidx.navigation3.ui, androidx.navigation3.runtime, androidx.lifecycle.viewmodel.navigation3, and kotlinx.serialization.json dependencies.
• Jetsnack/app/src/main/java/com/example/jetsnack/ui/JetsnackApp.kt
  • Replaced AnimatedVisibilityScope with AnimatedVisibility and togetherWith for transitions.
  • Removed NavHost and rememberJetsnackNavController.
  • Introduced rememberNavBackStack and NavDisplay for navigation management.
  • Refactored MainContainer logic directly into JetsnackApp.
  • Implemented conditional display of JetsnackBottomBar based on SnackDetailKey.
  • Updated navigation calls to use NavBackStack methods and NavKeys.
  • Removed LocalNavAnimatedVisibilityScope.
• Jetsnack/app/src/main/java/com/example/jetsnack/ui/components/Snacks.kt
  • Imported AnimatedContent and LocalNavAnimatedContentScope.
  • Replaced LocalNavAnimatedVisibilityScope with LocalNavAnimatedContentScope in SnackItem and HighlightSnackItem.
  • Updated JetsnackPreviewWrapper to use AnimatedContent and LocalNavAnimatedContentScope.
• Jetsnack/app/src/main/java/com/example/jetsnack/ui/home/DestinationBar.kt
  • Imported LocalNavAnimatedContentScope.
  • Replaced LocalNavAnimatedVisibilityScope with LocalNavAnimatedContentScope.
• Jetsnack/app/src/main/java/com/example/jetsnack/ui/home/Home.kt
  • Removed composableWithCompositionLocal and addHomeGraph functions.
  • Updated HomeSections enum to use NavKey objects instead of string routes.
  • Modified JetsnackBottomBar to accept NavKey for currentKey and an onItemClick callback.
• Jetsnack/app/src/main/java/com/example/jetsnack/ui/navigation/JetsnackNavController.kt
  • Removed the custom navigation controller file, as its functionality is now handled by Navigation 3's NavBackStack.
• Jetsnack/app/src/main/java/com/example/jetsnack/ui/navigation/NavKeys.kt
  • Added new file defining serializable NavKey data objects for FeedKey, SearchKey, CartKey, ProfileKey, and SnackDetailKey.
  • Added extension functions addHomeSection and addSnackDetail for NavBackStack<NavKey> management.
• Jetsnack/app/src/main/java/com/example/jetsnack/ui/snackdetail/SnackDetail.kt
  • Imported LocalNavAnimatedContentScope.
  • Replaced LocalNavAnimatedVisibilityScope with LocalNavAnimatedContentScope in various composables within the snack detail screen.
• Jetsnack/gradle/libs.versions.toml
  • Updated androidx-navigation version to androidx-navigation3.
  • Added androidx-lifecycle-navigation3 version.
  • Removed androidx-navigation-compose, androidx-navigation-fragment, androidx-navigation-ui-ktx library definitions.
  • Added androidx-navigation3-runtime, androidx-navigation3-ui, and androidx-lifecycle-viewmodel-navigation3 library definitions.
  • Added navigation3 version definition.

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[gemini-code-assist]

Code Review

This is a great migration to Navigation 3. It significantly simplifies the navigation structure by moving from nested NavHosts to a single back stack, which is much cleaner. The use of serializable NavKeys and NavDisplay is well-executed.

I've added a few comments, mostly focusing on ensuring runtime safety by restoring some null checks for navigation scopes that were removed during the refactoring. This will prevent potential NullPointerExceptions. I also included a suggestion to improve the 'clunky' logic for the bottom bar that you mentioned in your description, addressing both performance and redundant navigation triggers.

Overall, excellent work on this refactor!

[riggaroo]

I'm not sure why, but comparing between develop + this branch, the transition between the Feed and Cart composables looks a bit quicker, and doesn't seem like its performing a fadeIn or fadeOut. Doesn't look bad, I'm just wondering if there was a change missed here.
Not blocking on this one :)

[riggaroo]

Overall looking good! Just the bottom bar animation needs fixing.