Implement advanced deep link recipe #167

claraf3 · 2025-12-01T06:11:57Z

The recipe spans across two modules in order to simulate a real-world scenario where App A deeplinks into App B.

App A - com.example.nav3recipes.deeplink.advanced module
App B - advanceddeeplinkapp module

The goal of this recipe is to show how to:

Create a synthetic backStack
A synthetic backStack is created when the deep linked app is started as the root Activity of a new Task. This backStack is required in order to support proper Back & Up buttons.
Support Back / Up buttons
Back button brings user back to the previous screen, while the Up button brings user to the current screen's hierarchical parent. This requires synthetic backStack and Task stack management. See README for more info.

This PR contains three commits

Adding advanceddeeplinkapp module which is the app to deep link into
Pulling out common screens & resources into a :common module to be shared by basic and advanced deep link recipes
Adding the com.example.nav3recipes.deeplink.advanced module

Second app to show case deeplinking with new stack and up button

Contains common code shared between app and appdeeplink for deeplink recipes

gemini-code-assist · 2025-12-01T06:12:40Z

Summary of Changes

Hello @claraf3, 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 delivers a comprehensive advanced deep linking recipe, showcasing how to handle inter-app navigation, manage Android task stacks, and construct synthetic backstacks for consistent Back and Up button functionality. The changes also involve significant architectural improvements by extracting shared UI and data logic into a new common module, making the codebase more modular and maintainable.

Highlights

Advanced Deep Link Recipe Implementation: Introduced a new advanced deep link recipe that simulates a real-world scenario of 'App A' deep linking into 'App B', demonstrating complex navigation patterns.
Synthetic BackStack Management: Implemented logic to create and manage a synthetic backStack, crucial for supporting proper Back and Up button behavior when a deep-linked app is launched as the root Activity of a new Task.
Refactoring and Modularity: Refactored common UI components, data models, and utility functions into a new :common module, enhancing code reusability and improving overall project structure.
New Application Module for Deep Link Target: Created a dedicated Android application module (:appdeeplink) to serve as 'App B', the target for advanced deep links, complete with its own manifest, navigation keys, and utility classes.

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Code Review

This pull request successfully implements an advanced deep linking recipe, effectively demonstrating how to manage task stacks and create a synthetic back stack. The separation of concerns into app, appdeeplink, and common modules is a great approach that mimics a real-world scenario. The code is well-structured and the new README.md files provide excellent documentation for this complex topic. I've identified a few areas for improvement, including a potential crash due to unsafe URI parsing, some leftover debug code, and minor code refinements. My detailed comments and suggestions aim to enhance the robustness and clarity of the implementation.

appdeeplink/src/main/java/com/example/nav3recipes/deeplink/app/util/BackStackUtil.kt

app/src/main/java/com/example/nav3recipes/deeplink/advanced/AdvancedCreateDeepLinkActivity.kt

app/src/main/java/com/example/nav3recipes/deeplink/advanced/CreateAdvancedDeepLinkActivity.kt

appdeeplink/src/main/java/com/example/nav3recipes/deeplink/app/Nav3RecipesDeeplinkApp.kt

appdeeplink/src/main/java/com/example/nav3recipes/deeplink/app/util/Navigator.kt

The recipe spans across two modules in order to simulate a real-world scenario where `App A` deeplinks into `App B`. The goal of this recipe is to show how to: 1. Create a synthetic backStack A synthetic backStack is created when the deeplinked app is started as the root Activity of a new Task. This backStack is required in order to support proper Back & Up buttons. 2. Support Back / Up buttons Back button brings user back to the prevoius screen, while the Up button brings user to the current screen's hierarhical parent. This requires synthetic backStack and Task stack management. See README for more info.

jbw0033

Can you make this not touch the basic sample code at all? It is okay to duplicate things here if needed.

I think the most important thing for these samples is that it is clear what code is required for advanced deep linking separate from helper functions for just navigating and what code is required for advanced deep linking vs the basic sample.

We can worry about clean up later.

claraf3 · 2025-12-01T21:15:05Z

Can you make this not touch the basic sample code at all? It is okay to duplicate things here if needed.

I think the most important thing for these samples is that it is clear what code is required for advanced deep linking separate from helper functions for just navigating and what code is required for advanced deep linking vs the basic sample.

If anything, extracting the Screens out into a separate :common module should help separate what is deep link related and what is just for looks. The extracted screens are just UI pieces unrelated to deep link.

With that, the remaining code in deeplink.basic and deeplink.advanced and deeplink.app are core as in they contain

The CreateAdvancedDeepLinkActivity to create deep links with
The util package for deep link specific helpers
The MainActivity that you deeplink into
NavRecipeKey - the NavKeys

Is any part confusing / too blended?

Guide that covers basic principles of deep linking and demonstrates how to apply them in Navigation 3

claraf3 · 2025-12-02T05:20:33Z

Added the deeplink-guide.md into this PR

claraf3 · 2025-12-02T22:40:31Z

Spoke with Jeremy offline. Rename some classes and packages to clarify that the second app is for advanced deep link recipe.

app/src/main/java/com/example/nav3recipes/deeplink/basic/README.md

Rename second app to advanceddeeplinkapp and reuse the same deeplink.advanced package

app/src/main/java/com/example/nav3recipes/deeplink/advanced/README.md

dturner · 2025-12-03T19:49:44Z

advanceddeeplinkapp/build.gradle.kts

If at all possible, I would like to avoid creating separate modules in the recipes repo. Currently each recipe has its own activity - is it not possible to demonstrate the deep linking concepts by having separate activities for each deep link app?

We've explored how to represent different Task stacks without a second app module. Separate activities is not enough - we need to show the difference between an app's Activity in another App's Task, and the an app's Activity in its own Task. We do need a second app for this :(

If you deep link to another Activity within the same module, the Activity would still be started in the original Task even if you flagged it with Intent.FLAG_ACTIVITY_NEW_TASK

OK fair enough, thanks for clarifying.

dturner · 2025-12-03T19:56:07Z

...inkapp/src/main/java/com/example/nav3recipes/deeplink/advanced/util/DeepLinkBackStackUtil.kt

@@ -0,0 +1,175 @@
+package com.example.nav3recipes.deeplink.advanced.util


Use of util anywhere is usually a code smell - everything and anything can be a utility and it usually becomes a dumping ground for miscellaneous things.

I would prefer splitting this file to BackStackHelpers.kt, UriHelpers.kt etc. Then moving these files into the package above and removing util package.

dturner · 2025-12-03T19:58:19Z

advanceddeeplinkapp/src/main/java/com/example/nav3recipes/deeplink/advanced/NavRecipeKey.kt

+ * Up button (see [navigateUp] for more on this).
+ */
+
+internal interface NavRecipeKey: NavKey {


This would be better named RecipeNavKey as it's a recipe-specific NavKey.

dturner · 2025-12-03T19:58:34Z

advanceddeeplinkapp/src/main/java/com/example/nav3recipes/deeplink/advanced/NavRecipeKey.kt

+    val screenTitle: String
+}
+
+internal interface NavDeepLinkRecipeKey: NavRecipeKey {


Better as DeepLinkRecipeNavKey

dturner · 2025-12-03T20:01:03Z

advanceddeeplinkapp/src/main/res/drawable/ic_launcher_background.xml

Assuming there are no specific resources for the advanceddeeplinkapp, all these resources can be obtained from the app module (although better if we don't have separate modules at all).

I made a different launcher for second app on purpose so that you can tell which app the Activity is started on,

i.e. on old Task you'd see App A's launcher icon, on new Task you'd see App B's launcher icon.

dturner · 2025-12-03T20:03:12Z

app/src/main/java/com/example/nav3recipes/deeplink/basic/NavRecipeKey.kt

+import com.example.nav3recipes.deeplink.basic.ui.STRING_LITERAL_USERS
+import kotlinx.serialization.Serializable
+
+internal interface NavRecipeKey: NavKey {


RecipeNavKey

dturner · 2025-12-03T20:09:23Z

common/src/main/kotlin/com/example/nav3recipes/deeplink/common/Screens.kt


 @Composable
-internal fun EntryScreen(text: String, content: @Composable () -> Unit = { }) {
+public fun EntryScreen(text: String, content: @Composable () -> Unit = { }) {


nit: functions are public by default in kotlin so public is redundant unless you've enabled explicit API mode (which we haven't)

dturner · 2025-12-03T20:11:46Z

common/src/main/kotlin/com/example/nav3recipes/deeplink/common/Screens.kt


 @Composable
-internal fun EntryScreen(text: String, content: @Composable () -> Unit = { }) {
+public fun EntryScreen(text: String, content: @Composable () -> Unit = { }) {


There's a composable that does almost exactly this already in the app's content/Content.kt file called ContentBase. See the other recipes for usage.

Maybe we should move the content package into the :common module.

Good idea. Might as well since :common is there now.

dturner · 2025-12-03T20:21:16Z

common/build.gradle.kts

+    implementation(libs.androidx.adaptive.layout)
+    implementation(platform(libs.androidx.compose.bom))
+
+    implementation(libs.kotlinx.serialization.core)


Are all these dependencies needed for the common module?

dturner · 2025-12-03T20:23:13Z

common/src/main/kotlin/com/example/nav3recipes/deeplink/common/Screens.kt

-internal fun FriendsList(users: List<User>) {
+public fun FriendsList(
+    users: List<User>,
+    onClick: ((user: User) -> Unit)? = null


Suggested change

onClick: ((user: User) -> Unit)? = null

onUserClick: ((user: User) -> Unit)? = null

claraf3 added 2 commits November 30, 2025 21:56

Add deeplink app

485a657

Second app to show case deeplinking with new stack and up button

Add common module

78fdb71

Contains common code shared between app and appdeeplink for deeplink recipes

claraf3 requested review from dturner, ianhanniballake and jbw0033 as code owners December 1, 2025 06:11

gemini-code-assist bot reviewed Dec 1, 2025

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claraf3 force-pushed the cf/advanced-recipe branch 2 times, most recently from 9f9e755 to 88c51d1 Compare December 1, 2025 17:30

claraf3 force-pushed the cf/advanced-recipe branch from 88c51d1 to eb5de52 Compare December 1, 2025 17:33

jbw0033 reviewed Dec 1, 2025

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claraf3 mentioned this pull request Dec 2, 2025

Add deeplink-guide.md #168

Closed

Add deeplink-guide

e5cfc90

Guide that covers basic principles of deep linking and demonstrates how to apply them in Navigation 3

claraf3 force-pushed the cf/advanced-recipe branch from 8f2eaea to e5cfc90 Compare December 2, 2025 05:19

claraf3 requested a review from jbw0033 December 2, 2025 22:40

ianhanniballake approved these changes Dec 2, 2025

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app/src/main/java/com/example/nav3recipes/deeplink/basic/README.md Outdated Show resolved Hide resolved

Rename advanced deeplink app and package

b2ef58c

Rename second app to advanceddeeplinkapp and reuse the same deeplink.advanced package

claraf3 force-pushed the cf/advanced-recipe branch from 35f3b4b to b2ef58c Compare December 3, 2025 01:23

claraf3 merged commit 861030d into android:main Dec 3, 2025
2 checks passed

dturner reviewed Dec 3, 2025

View reviewed changes

		@@ -0,0 +1,175 @@
		package com.example.nav3recipes.deeplink.advanced.util

	onClick: ((user: User) -> Unit)? = null
	onUserClick: ((user: User) -> Unit)? = null

Implement advanced deep link recipe #167

Implement advanced deep link recipe #167

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