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Migrate Jetnews to Navigation 3 (#1675)
## Key Changes * Created `NavKey` objects and classes to replace the `JetnewsDestinations` object. * Refactored the home route to only be responsible for displaying the list of posts and moved the post detail UI and logic into its own route. * Implemented a `ListDetailSceneStrategy` to display the post detail view alongside the list of posts if the window width size class is at least expanded. * Added `NavigationState` and `Navigator` classes and helpers for storing and modifying the app's navigation state. * Replaced `JetnewsNavGraph` with `JetnewsNavDisplay`. * Removed Navigation 2 dependencies * Implemented support for deeplinks for the home page, post detail page, and interest page. * Improved the `app_opensArticle` (now `app_opensPost`) test so that it now actually tests that the post content is displayed.
2 parents 1bf1c20 + c4eed0b commit 120496e

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‎JetNews/README.md‎

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@@ -15,23 +15,28 @@ project from Android Studio following the steps
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## Features
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This sample contains three screens: a list of articles, a detail page for articles, and a page to
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subscribe to topics of interest. The navigation from the the list of articles to the interests
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This sample contains three screens: a list of posts, a detail page for a post, and a page to
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subscribe to topics of interest. The navigation from the list of posts to the interests
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screen uses a navigation drawer.
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### App scaffolding
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Package [`com.example.jetnews.ui`][1]
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[`JetnewsApp.kt`][2] arranges the different screens in the `NavDrawerLayout`.
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[`JetnewsApp.kt`][2] sets up the app's navigation state and the modal drawer used for navigation
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on smaller windows.
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[`JetnewsNavGraph.kt`][3] configures the navigation routes and actions in the app.
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[`JetnewsNavDisplay.kt`][3] displays the primary content of the app: the list of posts, the
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posts themselves, and the interests page. It uses a list-detail scene strategy to adaptively
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display more or less content depending on the window size.
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<img src="screenshots/jetnews_all_screens.png" alt="Screenshot">
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[1]: app/src/main/java/com/example/jetnews/ui
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[2]: app/src/main/java/com/example/jetnews/ui/JetnewsApp.kt
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[3]: app/src/main/java/com/example/jetnews/ui/JetnewsNavGraph.kt
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[3]: app/src/main/java/com/example/jetnews/ui/JetnewsNavDisplay.kt
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### Main article list
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### Main post list
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Package [`com.example.jetnews.ui.home`][4]
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[4]: app/src/main/java/com/example/jetnews/ui/home
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### Article detail
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### Post detail
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Package [`com.example.jetnews.ui.article`][5]
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Package [`com.example.jetnews.ui.post`][5]
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This screen dives into the Text API, showing how to use different fonts than the ones defined in
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[`Typography`][6]. It also adds a bottom app bar, with custom actions.
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[5]: app/src/main/java/com/example/jetnews/ui/article
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[5]: app/src/main/java/com/example/jetnews/ui/post
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[6]: app/src/main/java/com/example/jetnews/ui/theme/Type.kt
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### Interests screen
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* To run Instrumented tests use the "Instrumented tests" run configuration or run the `./gradlew connectedCheck` command.
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* To run tests with Robolectric use the "Robolectric tests" run configuration or run the `./gradlew testDebug` command.
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## Jetnews for every screen
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<img src="screenshots/jetnews_all_screens.png" alt="Screenshot">
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We recently updated Jetnews to enhance its behavior across all mobile devices, both big and small.
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Jetnews already had support for “traditional” mobile screens, so it was tempting to describe all of
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our changes as “adding large screen support.” While that is true, it misses the point of having
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adaptive UI. For example, if your app is running in split screen mode on a tablet, it shouldn't try
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to display “tablet UI” unless it actually has enough space for it. With all of these changes,
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Jetnews is working better than ever on large screens, but also on small screens too.
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Check out the blog post that explains all the changes in more details:
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https://medium.com/androiddevelopers/jetnews-for-every-screen-4d8e7927752
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## License
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```

‎JetNews/app/build.gradle.kts‎

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plugins {
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alias(libs.plugins.android.application)
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alias(libs.plugins.kotlin.serialization)
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alias(libs.plugins.compose)
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}
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implementation(libs.kotlin.stdlib)
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implementation(libs.kotlinx.coroutines.android)
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implementation(libs.kotlinx.serialization.core)
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implementation(libs.androidx.compose.animation)
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implementation(libs.androidx.compose.foundation.layout)
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implementation(libs.androidx.compose.material3)
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implementation(libs.androidx.compose.material3.adaptive)
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implementation(libs.androidx.compose.materialWindow)
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implementation(libs.androidx.compose.runtime.livedata)
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implementation(libs.androidx.compose.ui.tooling.preview)
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implementation(libs.androidx.lifecycle.livedata.ktx)
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implementation(libs.androidx.lifecycle.viewModelCompose)
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implementation(libs.androidx.lifecycle.runtime.compose)
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implementation(libs.androidx.lifecycle.viewmodel.navigation3)
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implementation(libs.androidx.navigation.compose)
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implementation(libs.androidx.navigation3.runtime)
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implementation(libs.androidx.navigation3.ui)
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implementation(libs.androidx.window)
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androidTestImplementation(libs.junit)

‎JetNews/app/src/androidTest/java/com/example/jetnews/JetnewsTests.kt‎

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@@ -22,9 +22,8 @@ import androidx.compose.ui.test.hasText
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import androidx.compose.ui.test.junit4.createAndroidComposeRule
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import androidx.compose.ui.test.onNodeWithContentDescription
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import androidx.compose.ui.test.onNodeWithText
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import androidx.compose.ui.test.onRoot
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import androidx.compose.ui.test.performClick
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import androidx.compose.ui.test.printToString
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import androidx.compose.ui.test.performScrollTo
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import androidx.test.core.app.ApplicationProvider
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import androidx.test.ext.junit.runners.AndroidJUnit4
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import com.example.jetnews.data.posts.impl.manuel
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}
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@Test
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fun app_opensArticle() {
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println(composeTestRule.onRoot().printToString())
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composeTestRule.onAllNodes(hasText(manuel.name, substring = true))[0].performClick()
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println(composeTestRule.onRoot().printToString())
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try {
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composeTestRule.onAllNodes(hasText("3 min read", substring = true))[0].assertExists()
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} catch (e: AssertionError) {
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println(composeTestRule.onRoot().printToString())
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throw e
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}
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fun app_opensPost() {
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composeTestRule.onAllNodes(hasText(manuel.name, substring = true))[0]
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.performScrollTo()
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.performClick()
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composeTestRule.waitUntilExactlyOneExists(hasText("Use Dagger in Kotlin!", substring = true), 5000L)
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}
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@Test

‎JetNews/app/src/androidTest/java/com/example/jetnews/TestHelper.kt‎

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package com.example.jetnews
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import android.content.Context
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import androidx.compose.material3.windowsizeclass.WindowWidthSizeClass
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import androidx.compose.ui.test.junit4.ComposeContentTestRule
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import com.example.jetnews.ui.JetnewsApp
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import com.example.jetnews.ui.home.HomeKey
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/**
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* Launches the app from a test context
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setContent {
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JetnewsApp(
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appContainer = TestAppContainer(context),
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widthSizeClass = WindowWidthSizeClass.Compact,
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isBackEnabled = true,
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initialBackStack = listOf(HomeKey),
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)
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}
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}

‎JetNews/app/src/main/AndroidManifest.xml‎

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<activity
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android:name=".ui.MainActivity"
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android:exported="true"
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android:launchMode="singleTop"
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android:windowSoftInputMode="adjustResize">
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<intent-filter>
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<action android:name="android.intent.action.MAIN" />
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<intent-filter>
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<action android:name="android.intent.action.VIEW" />
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<category android:name="android.intent.category.BROWSABLE"/>
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<category android:name="android.intent.category.DEFAULT" />
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<data
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android:host="developer.android.com"
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android:pathPrefix="/jetnews"

‎JetNews/app/src/main/java/com/example/jetnews/deeplink/JetnewsDeeplinks.kt‎

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/*
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* Copyright 2026 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.jetnews.deeplink
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import android.net.Uri
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import androidx.navigation3.runtime.NavKey
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import com.example.jetnews.deeplink.util.DeepLinkMatcher
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import com.example.jetnews.deeplink.util.DeepLinkRequest
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import com.example.jetnews.deeplink.util.KeyDecoder
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import com.example.jetnews.ui.home.HomeDeepLinkPattern
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import com.example.jetnews.ui.interests.InterestsDeepLinkPattern
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import com.example.jetnews.ui.navigation.DeepLinkKey
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import com.example.jetnews.ui.post.PostDeepLinkPattern
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val JetnewsDeepLinkPatterns = listOf(HomeDeepLinkPattern, PostDeepLinkPattern, InterestsDeepLinkPattern)
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fun Uri.handleDeepLink(): List<NavKey>? {
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val deepLinkRequest = DeepLinkRequest(this)
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val deepLinkMatchResult = JetnewsDeepLinkPatterns.firstNotNullOfOrNull {
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DeepLinkMatcher(deepLinkRequest, it).match()
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} ?: return null
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val initialKey = KeyDecoder(deepLinkMatchResult.args).decodeSerializableValue(deepLinkMatchResult.serializer)
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return generateSequence(initialKey) { (it as? DeepLinkKey)?.parent }
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.toList()
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.asReversed()
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}

‎JetNews/app/src/main/java/com/example/jetnews/deeplink/util/DeepLinkMatcher.kt‎

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/*
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* Copyright 2026 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* https://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.jetnews.deeplink.util
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import android.util.Log
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import androidx.navigation3.runtime.NavKey
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import kotlinx.serialization.KSerializer
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internal class DeepLinkMatcher<T : NavKey>(val request: DeepLinkRequest, val deepLinkPattern: DeepLinkPattern<T>) {
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/**
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* Match a [DeepLinkRequest] to a [DeepLinkPattern].
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*
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* Returns a [DeepLinkMatchResult] if this matches the pattern, returns null otherwise
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*/
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fun match(): DeepLinkMatchResult<T>? {
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if (request.uri.scheme != deepLinkPattern.uriPattern.scheme) return null
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if (!request.uri.authority.equals(deepLinkPattern.uriPattern.authority, ignoreCase = true)) return null
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if (request.pathSegments.size != deepLinkPattern.pathSegments.size) return null
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// exact match (url does not contain any arguments)
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if (request.uri == deepLinkPattern.uriPattern)
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return DeepLinkMatchResult(deepLinkPattern.serializer, mapOf())
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val args = mutableMapOf<String, Any>()
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// match the path
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request.pathSegments
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.asSequence()
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// zip to compare the two objects side by side, order matters here so we
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// need to make sure the compared segments are at the same position within the url
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.zip(deepLinkPattern.pathSegments.asSequence())
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.forEach { it ->
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// retrieve the two path segments to compare
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val requestedSegment = it.first
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val candidateSegment = it.second
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// if the potential match expects a path arg for this segment, try to parse the
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// requested segment into the expected type
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if (candidateSegment.isParamArg) {
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val parsedValue = try {
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candidateSegment.typeParser.invoke(requestedSegment)
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} catch (e: IllegalArgumentException) {
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Log.e(TAG_LOG_ERROR, "Failed to parse path value:[$requestedSegment].", e)
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return null
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}
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args[candidateSegment.stringValue] = parsedValue
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} else if (requestedSegment != candidateSegment.stringValue) {
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// if it's path arg is not the expected type, its not a match
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return null
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}
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}
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// match queries (if any)
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request.queries.forEach { query ->
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val name = query.key
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// If the pattern does not define this query parameter, ignore it.
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// This prevents a NullPointerException.
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val queryStringParser = deepLinkPattern.queryValueParsers[name] ?: return@forEach
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val queryParsedValue = try {
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queryStringParser.invoke(query.value)
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} catch (e: IllegalArgumentException) {
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Log.e(TAG_LOG_ERROR, "Failed to parse query name:[$name] value:[${query.value}].", e)
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return null
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}
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args[name] = queryParsedValue
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}
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// provide the serializer of the matching key and map of arg names to parsed arg values
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return DeepLinkMatchResult(deepLinkPattern.serializer, args)
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}
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}
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/**
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* Created when a requested deeplink matches with a supported deeplink
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*
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* @param [T] the backstack key associated with the deeplink that matched with the requested deeplink
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* @param serializer serializer for [T]
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* @param args The map of argument name to argument value. The value is expected to have already
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* been parsed from the raw url string back into its proper KType as declared in [T].
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* Includes arguments for all parts of the uri - path, query, etc.
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* */
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internal data class DeepLinkMatchResult<T : NavKey>(val serializer: KSerializer<T>, val args: Map<String, Any>)
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const val TAG_LOG_ERROR = "Nav3RecipesDeepLink"

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