Android Weekly Issue #463

Room auto-migrations

Room 2.4.0-alpha01推出了Auto migration, 让数据库迁移更加容易.

@Database(
   version = 2,
   entities = [ GoodDoggos.class ],
   autoMigrations = [
        AutoMigration (
            from = 1, 
            to = 2,
            spec = DoggosDatabase.DoggosAutoMigration::class
       )
    ]
)
abstract class DoggosDatabase : RoomDatabase {   
  @RenameTable(fromTableName = "Doggos", toTableName = "GoodDoggos")
    class DoggosAutoMigration: AutoMigrationSpec {   }
}

自动迁移可以和手动迁移结合, 满足开发者的需求.

对于自动迁移还有测试的支持.

A Compose & Viewmodel integration test with Hilt

一个简单的小例子, UI是用Compose, 注入用Hilt.

ViewModel中的state类型:

sealed class UiState {
    object Loading : UiState()
    object Empty : UiState()
    data class Content(val items: List<Item> = listOf()) : UiState()
}

Repository返回flow, flow转UiState的方法:

private suspend fun Flow<List<Item>>.toUiState(): Flow<UiState> = map {
    if (it.isEmpty()) {
        UiState.Empty
    } else {
        UiState.Content(items = it)
    }
}.onStart {
    emit(UiState.Loading)
}

测试的时候, 需要假数据, 所以替换掉了Repository:

@TestInstallIn(components = [SingletonComponent::class],
    replaces = [InventoryRepositoryModule::class])
@Module
object FakeInventoryRepositoryModule {
    @Singleton
    @Provides
    fun provideFakeInventoryRepository() = object : InventoryRepository {
        @ExperimentalCoroutinesApi
        override suspend fun items(): Flow<List<Item>> {
            return flowOf(dummyItems)
        }
    }
}

需要test runner:

class HiltTestRunner : AndroidJUnitRunner() {
    override fun newApplication(
        cl: ClassLoader?,
        className: String?,
        context: Context?,
    ): Application {
        return super.newApplication(cl, HiltTestApplication::class.java.name, context)
    }
}

最后测试写成这样:

@ExperimentalCoroutinesApi
@HiltAndroidTest
class ItemListTest {

    @get:Rule(order = 1)
    var hiltTestRule = HiltAndroidRule(this)

    @get:Rule(order = 2)
    var composeTestRule = createAndroidComposeRule<MainActivity>()

    @Before
    fun setup() {
        hiltTestRule.inject()
        composeTestRule.setContent {
            TallyApp(composeTestRule.activity.viewModels<ListViewModel>().value)
        }
    }

    @Test
    fun app_displays_list_of_items() {
        //assert the list is displayed
        composeTestRule.onNodeWithTag(InventoryListTag).assertIsDisplayed()

        //assert all items exist within the tree
        dummyItems.forEach { item -> 
            composeTestRule.onNodeWithText(item.name).assertExists()
        }
    }
}

Tap Response Time: Jetpack Navigation

关于点击响应时间的进一步探索.

Navigation Drawer using Jetpack Compose

Navigation Drawer的Compose实现.

代码见:
https://github.com/walnashgit/ComposeNavigationDrawer/tree/feature/ComposeNavDrawerUsingModalDrawer

Unit testing on Android

单元测试:

• ViewModel
• 自定义View
• 扩展方法

测试LiveData还有一个工具类.

Lessons learned when migrating my app to Jetpack Compose

一些经验和资源介绍.

Getting ready for Declarative UIs — Part 3 — Why Declarative UIs on Android?

为什么要用声明式UI.

• 首先讲了有限状态机.
• Interoperability的实例.
• 保存变量除了有remember之外还有Composition Local.
• 关于SideEffect推荐阅读这篇文章.
• 关于单向数据流, 看这篇文章.
• Screenshot testing: https://blog.karumi.com/jetpack-compose-screenshot-testing-with-shot/

CoroutineScope and coroutineContexts

关于测试中CoroutineContext的探讨.

always keep currentCoroutineContext() and coroutineContext pointing to the same value.

Pi Practice App in Compose

一个小应用, 之前使用Anko做的, 现在改用Compose做了.

Code

• https://github.com/skydoves/Lazybones 流式的生命周期订阅相关
• https://github.com/igorescodro/alkaa 一个todo app.