https://github.com/mercari/nav-entry-scope-android
This project offers an implementation for the NavEntryScope pattern used for sharing dependencies across multiple ViewModels on the same screen.
https://github.com/mercari/nav-entry-scope-android
android dependency-injection hilt kotlin library
Last synced: 6 months ago
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This project offers an implementation for the NavEntryScope pattern used for sharing dependencies across multiple ViewModels on the same screen.
- Host: GitHub
- URL: https://github.com/mercari/nav-entry-scope-android
- Owner: mercari
- License: mit
- Created: 2025-11-16T23:42:45.000Z (8 months ago)
- Default Branch: main
- Last Pushed: 2025-12-18T06:29:46.000Z (6 months ago)
- Last Synced: 2025-12-20T18:16:14.206Z (6 months ago)
- Topics: android, dependency-injection, hilt, kotlin, library
- Language: Kotlin
- Homepage:
- Size: 135 KB
- Stars: 4
- Watchers: 1
- Forks: 0
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE.txt
Awesome Lists containing this project
README
# NavEntryScope library and annotation processor
[](https://github.com/mercari/nav-entry-scope-android/actions/workflows/ci.yml)
[](LICENSE.txt)
[](https://central.sonatype.com/artifact/com.mercari/nav-entry-scope)
[](https://central.sonatype.com/artifact/com.mercari/nav-entry-scope-processor)
This project offers an implementation for the **NavEntryScope** pattern used for sharing dependencies across multiple ViewModels on the same screen, along with a sample app.
To learn more, check out the droidcon Italy Slides: [Slide Deck](https://speakerdeck.com/bxttx/beyond-hilts-built-in-scopes-scope-shared-dependencies-to-the-current-screen)
## What is NavEntryScope?
In single-activity Android apps with Compose navigation, screens often have multiple ViewModels that need to share data. The existing Hilt scopes don't fit this use case well:
- `@Singleton` / `@ActivityRetainedScoped`: Too broad because shared across all screens, causing state leakage between multiple instances of the same screen in the back stack
- `@ViewModelScoped`: Too narrow because each ViewModel gets its own instance, making sharing impossible
**NavEntryScope** is a custom Hilt scope that provides screen-level scoping. Dependencies annotated with `@NavEntryScoped` are:
- Shared across all ViewModels on the same screen
- Isolated per navigation entry: each screen instance gets its own dependencies
- Automatically cleaned up when the screen is removed from the back stack
## When to Use NavEntryScope
Use NavEntryScope when you have:
- Multiple ViewModels on the same screen that depend on shared data
- Complex screens where a single ViewModel would become too large
- Reusable UI components with their own ViewModels that need access to screen-level data
- Multiple instances of the same screen in the navigation back stack
## How to Use
### 1. Add Dependencies
Add the library and annotation processor to your module's `build.gradle.kts`:
```kotlin
dependencies {
implementation("com.mercari:nav-entry-scope:")
ksp("com.mercari:nav-entry-scope-processor:")
}
```
Replace `` with the latest version shown in the badge above.
### 2. Annotate Shared Dependencies
```kotlin
@Module
@InstallIn(NavEntryComponent::class)
interface YourModule {
@Binds
@NavEntryScoped
fun bindRepository(impl: YourRepositoryImpl): YourRepository
}
```
### 3. Inject into ViewModels
ViewModels remain standard `@HiltViewModel` classes. Injecting a dependency that depends on `@NavEntryScoped` into your ViewModel is also supported.
```kotlin
@HiltViewModel
class YourViewModel @Inject constructor(
private val repository: YourRepository // NavEntryScoped
) : ViewModel()
```
### 4. Use in Compose
Replace `hiltViewModel()` with `navEntryScopedViewModel()`:
```kotlin
@Composable
fun YourScreen() {
val viewModel: YourViewModel = navEntryScopedViewModel()
// ...
}
```
The annotation processor automatically generates the necessary Dagger modules (`NavEntry_Module`) and entry points (`NavEntry_EntryPoint`) to bridge `NavEntryComponent` and `ViewModelComponent`.
## Project Structure
### [`app`](app/)
Sample application demonstrating NavEntryScope usage with:
- `SharedCounterRepository` - A `@NavEntryScoped` repository holding the shared value
- `CounterLabelViewModel` - Displays the counter value
- `IncrementButtonViewModel` - Increments the counter
Both ViewModels access the same repository instance, demonstrating data sharing on a single screen.
### [`nav-entry-scope/lib`](nav-entry-scope/lib/)
Core library providing:
- `@NavEntryScoped` - Scope annotation for navigation entry lifetime
- `NavEntryComponent` - Custom Dagger component definition
- `NavEntryComponentOwner` - ViewModel managing component lifecycle
- `navEntryScopedViewModel()` - Compose function for injecting ViewModels with NavEntryScoped dependencies
### [`nav-entry-scope/processor`](nav-entry-scope/processor/)
Annotation processor (KSP) that generates:
- `NavEntry_EntryPoint` - Hilt EntryPoint interface installed in `NavEntryComponent`
- `NavEntry_Module` - Dagger module installed in `ViewModelComponent` that provides NavEntryScoped dependencies
## Local Development
### Testing Changes Locally
To test library changes immediately in the sample app, publish to Maven Local:
```bash
./gradlew publishToMavenLocal
```
The sample app is already configured to use `mavenLocal()`, so changes will be picked up on the next build.
### Using Snapshots
To use snapshot versions of the library, add the snapshot repository to your `settings.gradle.kts`:
```kotlin
dependencyResolutionManagement {
repositories {
maven("https://central.sonatype.com/repository/maven-snapshots/")
mavenCentral()
}
}
```
Then use the snapshot version in your dependencies:
```kotlin
implementation("com.mercari:nav-entry-scope:-SNAPSHOT")
ksp("com.mercari:nav-entry-scope-processor:-SNAPSHOT")
```
## Contribution
If you want to submit a PR for bug fixes or documentation, please read the [CONTRIBUTING.md](CONTRIBUTING.md) and follow the instruction beforehand.
## License
nav-entry-scope-android is released under the [MIT License](LICENSE.txt).