DroidKaigi 2021 official app
Guides
Development
Features
Now this app has the Feed feature. We will deliver Feed and events related to DroidKaigi.
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Design
Try it out
The builds being distributed through mobile app distribution services.
- Production (TBR)
- Try the latest staging through
- and more... (tbw)
Contributing
We always welcome any and all contributions! See CONTRIBUTING.md for more information
For Japanese speakers, please see CONTRIBUTING.ja.md
Requirements
Latest Android Studio BumbleBee and higher. You can download it from this page. Xcode version is 12.5.1 (If you do iOS development)
Tech Stacks
Kotlin Multiplatform
TBD
Jetpack Compose
Modern Development
- Jetpack Compose
- Kotlin Coroutines & Flows
- Dagger Hilt
- DataStore
- Kotlin Multiplatform
Architecture
Unidirectional data flow
Compose processing and ViewModel processing are performed by Unidirectional data flow.
Compose unidirectional data flow
By performing State hoisting(pass the value and receive the event), Jetpack Compose displays with unidirectional data flow.
/**
* stateful
*/
@Composable
fun FeedScreen(
onNavigationIconClick: () -> Unit,
onDetailClick: (Feed) -> Unit,
) {
...
val (
state,
effectFlow,
dispatch,
) = use(feedViewModel())
val context = LocalContext.current
effectFlow.collectInLaunchedEffect { effect ->
when (effect) {
is FeedViewModel.Effect.ErrorMessage -> {
scaffoldState.snackbarHostState.showSnackbar(
effect.appError.getReadableMessage(context)
)
}
}
}
FeedScreen(
// ...
FeedContents = state.filteredFeedContents,
onFavoriteChange = {
dispatch(FeedViewModel.Event.ToggleFavorite(Feed = it))
},
// ...
)
}
/**
* stateless
*/
@Composable
private fun FeedScreen(
// ...
FeedContents: FeedContents,
onFavoriteChange: (Feed) -> Unit,
// ...
) {
Column {
BackdropScaffold(
backLayerBackgroundColor = MaterialTheme.colors.primarySurface,
scaffoldState = scaffoldState,
backLayerContent = {
BackLayerContent(filters, onFavoriteFilterChanged)
}
// ...
)
// ...
}
}
ViewModel unidirectional data flow
This app handles the ViewModel with an MVI-like interface.
Compose
val (
state,
effectFlow,
dispatch,
) = use(feedViewModel())
val context = LocalContext.current
effectFlow.collectInLaunchedEffect { effect ->
when (effect) {
is FeedViewModel.Effect.ErrorMessage -> {
scaffoldState.snackbarHostState.showSnackbar(
effect.appError.getReadableMessage(context)
)
}
}
}
FeedScreen(
// ...
FeedContents = state.filteredFeedContents,
onFavoriteChange = {
dispatch(FeedViewModel.Event.ToggleFavorite(Feed = it))
},
// ...
This state, effectFlow and dispatch are created from ViewModel.
state represents the state that the UI should display.
effectFlow represents a one-time event such as a Snackbar display.
And dispatch represents a change of state.
ViewModel Interface
interface UnidirectionalViewModel<EVENT, EFFECT, STATE> {
val state: StateFlow<STATE>
val effect: Flow<EFFECT>
fun event(event: EVENT)
}
use(viewModel) function
@Composable
inline fun <reified STATE, EFFECT, EVENT> use(
viewModel: UnidirectionalViewModel<EVENT, EFFECT, STATE>,
):
StateEffectDispatch<STATE, EFFECT, EVENT> {
val state by viewModel.state.collectAsState()
val dispatch: (EVENT) -> Unit = { event ->
viewModel.event(event)
}
return StateEffectDispatch(
state = state,
effectFlow = viewModel.effect,
dispatch = dispatch
)
}
Testable & Previewable & Faster debug
Jetpack Compose is still a new technology. We are thinking of best practices. We will try to improve testing, preview and build by using Fake. For example, this app allows you to interact with the Android Studio Preview as if it were a real app.
This is possible by creating a Fake ViewModel and making it reliable.
How to make Fake's ViewModel reliable
Do the same test for Fake and the real thing by testing against the interface. This makes Fake's ViewModel reliable. This technique of doing the same test against Fake was introduced in "Build testable apps for Android" session(Google I/O'19).
You can also prevent forgetting to update by forcing the implementation with interface and . Also, by forcing the implementation with interface and " Exhaustive ", it is possible to prevent forgetting to update Fake's ViewModel.
override fun event(event: FeedViewModel.Event) {
coroutineScope.launch {
@Exhaustive
when (event) {
is FeedViewModel.Event.ChangeFavoriteFilter -> {
How to make it previewable and testable
This app uses fake's ViewModel to enable preview.
@Preview(showBackground = true)
@Composable
fun FeedScreenPreview() {
Conferenceapp2021FeedTheme(false) {
ProvideFeedViewModel(viewModel = fakeFeedViewModel()) {
FeedScreen {
}
}
}
}
How to debug fast?
If you want to check the UI display, you can check it in the Preview of Android Studio. In that case, the required task is :uicomponent-compose:main:compileDebugKotlin. Therefore, there is no need to build the data module that contains the definitions such as API and the build of Android dex, so you can quickly build and check. Also, changes to the data layer do not affect the ui module, so you can build faster.
Overall architecture
Thanks
Thank you for contributing!
Contributors
GitHub : Contributors
Designer
Trouble Shooting
Android Gradle plugin requires Java 11 to run. You are currently using Java 1.X
JDK 1.8 is a requirement to build an Android project basically, but AGP 7.0 requires JDK 11. Please make sure you are using Java 11. Please note that the java version of Gradle Daemon is determined at the launch-time, so ./gradlew --stop might be required for you.
The option 'android.enableBuildCache' is deprecated.
android.enableBuildCache is REMOVED in AGP 7.0. android.enableBuildCache=false has no issue but builds randomly succeed with true value. This may affect to those who declare android.enableBuildCache=true in their $GRADLE_USER_HOME/gradle.properties.
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