使用Ktor和SQLDelight创建跨平台应用

配置SQLDelight

SQLDelight库支持从SQL查询生成类型安全的Kotlin数据库API。编译期间，生成器会验证SQL查询并将其转换为可在共享模块中使用的Kotlin代码。

SQLDelight依赖已包含在项目中。要配置该库，打开shared/build.gradle.kts文件并添加sqldelight {}块：

packageName参数指定生成Kotlin源代码的包名。按提示同步Gradle项目文件。

生成数据库API

首先创建包含所有必要SQL查询的.sq文件。默认情况下SQLDelight插件在源集的sqldelight目录查找.sq文件：

1. 在shared/src/commonMain目录创建sqldelight新目录

2. 在sqldelight目录下创建com/jetbrains/spacetutorial/cache嵌套包目录

3. 在cache目录创建与build.gradle.kts中同名的AppDatabase.sq文件

4. 添加创建发射数据表的代码：

   import kotlin.Boolean; CREATE TABLE Launch ( flightNumber INTEGER NOT NULL, missionName TEXT NOT NULL, details TEXT, launchSuccess INTEGER AS Boolean DEFAULT NULL, launchDateUTC TEXT NOT NULL, patchUrlSmall TEXT, patchUrlLarge TEXT, articleUrl TEXT );

5. 添加插入数据的insertLaunch函数：

   insertLaunch: INSERT INTO Launch(flightNumber, missionName, details, launchSuccess, launchDateUTC, patchUrlSmall, patchUrlLarge, articleUrl) VALUES(?, ?, ?, ?, ?, ?, ?, ?);

6. 添加清空数据的removeAllLaunches函数：

   removeAllLaunches: DELETE FROM Launch;

7. 声明检索数据的selectAllLaunchesInfo函数：

   selectAllLaunchesInfo: SELECT Launch.* FROM Launch;

8. 运行以下命令生成对应的AppDatabase接口：

   ./gradlew generateCommonMainAppDatabaseInterface

   生成的Kotlin代码存储在shared/build/generated/sqldelight目录

创建平台特定数据库驱动工厂

要初始化AppDatabase接口，需要向其传递SqlDriver实例。SQLDelight提供多种平台特定的SQLite驱动实现，因此需要为每个平台单独创建这些实例。

虽然可以通过预期与实际声明实现，但本项目将使用Koin来体验Kotlin跨平台的依赖注入。

1. 在shared/src/commonMain/kotlin目录创建com/jetbrains/spacetutorial/cache包路径

2. 在cache目录创建DatabaseDriverFactory接口：

   package com.jetbrains.spacetutorial.cache import app.cash.sqldelight.db.SqlDriver interface DatabaseDriverFactory { fun createDriver(): SqlDriver }

3. 为Android实现该接口：在shared/src/androidMain/kotlin目录创建com.jetbrains.spacetutorial.cache包及DatabaseDriverFactory.kt文件

4. 在Android上通过AndroidSqliteDriver类实现驱动：

   package com.jetbrains.spacetutorial.cache import android.content.Context import app.cash.sqldelight.db.SqlDriver import app.cash.sqldelight.driver.android.AndroidSqliteDriver class AndroidDatabaseDriverFactory(private val context: Context) : DatabaseDriverFactory { override fun createDriver(): SqlDriver { return AndroidSqliteDriver(AppDatabase.Schema, context, "launch.db") } }

5. 对于iOS，在shared/src/iosMain/kotlin目录创建相同包结构及文件：

   package com.jetbrains.spacetutorial.cache import app.cash.sqldelight.db.SqlDriver import app.cash.sqldelight.driver.native.NativeSqliteDriver class IOSDatabaseDriverFactory : DatabaseDriverFactory { override fun createDriver(): SqlDriver { return NativeSqliteDriver(AppDatabase.Schema, "launch.db") } }

后续将在平台特定代码中实现这些驱动的实例。

实现缓存

现已添加平台数据库驱动工厂和AppDatabase接口来执行数据库操作。接下来创建包装AppDatabase接口并包含缓存逻辑的Database类。

1. 在公共源集shared/src/commonMain/kotlin的com.jetbrains.spacetutorial.cache目录创建Database类

2. 通过构造函数传递抽象的DatabaseDriverFactory实例：

   package com.jetbrains.spacetutorial.cache internal class Database(databaseDriverFactory: DatabaseDriverFactory) { private val database = AppDatabase(databaseDriverFactory.createDriver()) private val dbQuery = database.appDatabaseQueries }

   该类可见性设为internal，表示仅限跨平台模块内部访问

3. 在Database类中实现数据处理操作。首先创建返回所有火箭发射列表的getAllLaunches函数：

   import com.jetbrains.spacetutorial.entity.Links import com.jetbrains.spacetutorial.entity.Patch import com.jetbrains.spacetutorial.entity.RocketLaunch internal class Database(databaseDriverFactory: DatabaseDriverFactory) { // ... internal fun getAllLaunches(): List<RocketLaunch> { return dbQuery.selectAllLaunchesInfo(::mapLaunchSelecting).executeAsList() } private fun mapLaunchSelecting( flightNumber: Long, missionName: String, details: String?, launchSuccess: Boolean?, launchDateUTC: String, patchUrlSmall: String?, patchUrlLarge: String?, articleUrl: String? ): RocketLaunch { return RocketLaunch( flightNumber = flightNumber.toInt(), missionName = missionName, details = details, launchDateUTC = launchDateUTC, launchSuccess = launchSuccess, links = Links( patch = Patch( small = patchUrlSmall, large = patchUrlLarge ), article = articleUrl ) ) } }

4. 添加清空数据库并插入新数据的clearAndCreateLaunches函数：

   internal class Database(databaseDriverFactory: DatabaseDriverFactory) { // ... internal fun clearAndCreateLaunches(launches: List<RocketLaunch>) { dbQuery.transaction { dbQuery.removeAllLaunches() launches.forEach { launch -> dbQuery.insertLaunch( flightNumber = launch.flightNumber.toLong(), missionName = launch.missionName, details = launch.details, launchSuccess = launch.launchSuccess ?: false, launchDateUTC = launch.launchDateUTC, patchUrlSmall = launch.links.patch?.small, patchUrlLarge = launch.links.patch?.large, articleUrl = launch.links.article ) } } } }

添加网络访问权限

Android应用需要相应权限才能访问网络。在composeApp/src/androidMain/AndroidManifest.xml文件中添加：

添加依赖注入

Koin依赖注入允许声明可在不同上下文中使用的模块。本项目将创建两个模块：一个用于Android应用，另一个用于iOS应用。

声明包含Android组件的Koin模块：

1. 在composeApp/src/androidMain/kotlin目录的com.jetbrains.spacetutorial包中创建AppModule.kt文件 声明两个单例：

   package com.jetbrains.spacetutorial import com.jetbrains.spacetutorial.cache.AndroidDatabaseDriverFactory import com.jetbrains.spacetutorial.network.SpaceXApi import org.koin.android.ext.koin.androidContext import org.koin.dsl.module val appModule = module { single<SpaceXApi> { SpaceXApi() } single<SpaceXSDK> { SpaceXSDK( databaseDriverFactory = AndroidDatabaseDriverFactory( androidContext() ), api = get() ) } }

   SpaceXSDK类构造函数注入了平台特定的AndroidDatabaseDriverFactory类

2. 创建自定义Application类来启动Koin模块 在AppModule.kt旁创建Application.kt文件：

   package com.jetbrains.spacetutorial import android.app.Application import org.koin.android.ext.koin.androidContext import org.koin.core.context.GlobalContext.startKoin class MainApplication : Application() { override fun onCreate() { super.onCreate() startKoin { androidContext(this@MainApplication) modules(appModule) } } }

3. 在AndroidManifest.xml的<application>标签中指定MainApplication类：

   <manifest xmlns:android="http://schemas.android.com/apk/res/android"> ... <application ... android:name="com.jetbrains.spacetutorial.MainApplication"> ... </application> </manifest>

现在可以开始实现使用平台特定数据库驱动提供信息的UI

准备包含发射列表的视图模型

将使用Jetpack Compose和Material 3实现Android UI。首先创建使用SDK获取发射列表的视图模型，然后设置Material主题，最后编写组合函数整合所有内容。

1. 在composeApp/src/androidMain源集的com.jetbrains.spacetutorial包中创建RocketLaunchViewModel.kt文件：

   package com.jetbrains.spacetutorial import androidx.compose.runtime.State import androidx.compose.runtime.mutableStateOf import androidx.lifecycle.ViewModel import com.jetbrains.spacetutorial.entity.RocketLaunch class RocketLaunchViewModel(private val sdk: SpaceXSDK) : ViewModel() { private val _state = mutableStateOf(RocketLaunchScreenState()) val state: State<RocketLaunchScreenState> = _state } data class RocketLaunchScreenState( val isLoading: Boolean = false, val launches: List<RocketLaunch> = emptyList() )

   RocketLaunchScreenState实例将存储从SDK接收的数据和请求的当前状态

2. 添加在视图模型协程作用域中调用SDKgetLaunches函数的loadLaunches函数：

   import androidx.lifecycle.viewModelScope import kotlinx.coroutines.launch class RocketLaunchViewModel(private val sdk: SpaceXSDK) : ViewModel() { //... fun loadLaunches() { viewModelScope.launch { _state.value = _state.value.copy(isLoading = true, launches = emptyList()) try { val launches = sdk.getLaunches(forceReload = true) _state.value = _state.value.copy(isLoading = false, launches = launches) } catch (e: Exception) { _state.value = _state.value.copy(isLoading = false, launches = emptyList()) } } } }

3. 在类init {}块中添加loadLaunches()调用以在创建RocketLaunchViewModel对象时立即请求API数据：

   class RocketLaunchViewModel(private val sdk: SpaceXSDK) : ViewModel() { // ... init { loadLaunches() } }

4. 在AppModule.kt文件中将视图模型添加到Koin模块：

   import org.koin.androidx.viewmodel.dsl.viewModel val appModule = module { // ... viewModel { RocketLaunchViewModel(sdk = get()) } }

构建Material主题

主App()组合函数将围绕Material Theme提供的AppTheme函数构建：

1. 使用Material主题生成器生成Compose应用主题 完成后点击右上角Export并选择**Jetpack Compose (Theme.kt)**选项

2. 解压后将theme文件夹复制到composeApp/src/androidMain/kotlin/com/jetbrains/spacetutorial目录

   

3. 在每个主题文件Color.kt和Theme.kt中修改包声明：

   package com.jetbrains.spacetutorial.theme

4. 在Color.kt文件中添加表示成功与失败发射的颜色变量：

   val app_theme_successful = Color(0xff4BB543) val app_theme_unsuccessful = Color(0xffFC100D)

实现展示逻辑

创建应用的App()主组合函数，并从ComponentActivity类调用：

1. 在com.jetbrains.spacetutorial包的theme目录旁创建App.kt文件并添加组合函数：

   package com.jetbrains.spacetutorial import androidx.compose.material3.ExperimentalMaterial3Api import androidx.compose.material3.pulltorefresh.rememberPullToRefreshState import androidx.compose.runtime.Composable import androidx.compose.runtime.getValue import androidx.compose.runtime.remember import org.koin.androidx.compose.koinViewModel @OptIn( ExperimentalMaterial3Api::class ) @Composable fun App() { val viewModel = koinViewModel<RocketLaunchViewModel>() val state by remember { viewModel.state } val pullToRefreshState = rememberPullToRefreshState() if (pullToRefreshState.isRefreshing) { viewModel.loadLaunches() pullToRefreshState.endRefresh() } }

   使用Koin ViewModel API引用Android Koin模块中声明的viewModel

2. 添加实现加载屏幕、发射结果列和下拉刷新操作的UI代码：

   import com.jetbrains.spacetutorial.theme.AppTheme import com.jetbrains.spacetutorial.entity.RocketLaunch import com.jetbrains.spacetutorial.theme.app_theme_successful import com.jetbrains.spacetutorial.theme.app_theme_unsuccessful import androidx.compose.material3.HorizontalDivider import androidx.compose.material3.MaterialTheme import androidx.compose.material3.Scaffold import androidx.compose.material3.Text import androidx.compose.material3.TopAppBar import androidx.compose.material3.pulltorefresh.PullToRefreshContainer import androidx.compose.ui.Modifier import androidx.compose.ui.Alignment import androidx.compose.foundation.layout.Arrangement import androidx.compose.foundation.layout.Box import androidx.compose.foundation.layout.Column import androidx.compose.foundation.layout.Spacer import androidx.compose.foundation.layout.fillMaxSize import androidx.compose.foundation.layout.height import androidx.compose.foundation.layout.padding import androidx.compose.foundation.lazy.LazyColumn import androidx.compose.foundation.lazy.items import androidx.compose.ui.input.nestedscroll.nestedScroll import androidx.compose.ui.unit.dp @Composable fun App() { // ... AppTheme { Scaffold( topBar = { TopAppBar(title = { Text( "SpaceX Launches", style = MaterialTheme.typography.headlineLarge ) }) } ) { padding -> Box( modifier = Modifier .nestedScroll(pullToRefreshState.nestedScrollConnection) .fillMaxSize() .padding(padding) ) { if (state.isLoading) { Column( verticalArrangement = Arrangement.Center, horizontalAlignment = Alignment.CenterHorizontally, modifier = Modifier.fillMaxSize() ) { Text("Loading...", style = MaterialTheme.typography.bodyLarge) } } else { LazyColumn { items(state.launches) { launch: RocketLaunch -> Column(modifier = Modifier.padding(all = 16.dp)) { Text( text = "${launch.missionName} - ${launch.launchYear}", style = MaterialTheme.typography.headlineSmall ) Spacer(Modifier.height(8.dp)) Text( text = if (launch.launchSuccess == true) "Successful" else "Unsuccessful", color = if (launch.launchSuccess == true) app_theme_successful else app_theme_unsuccessful ) Spacer(Modifier.height(8.dp)) val details = launch.details if (details?.isNotBlank() == true) { Text( text = details ) } } HorizontalDivider() } } } PullToRefreshContainer( state = pullToRefreshState, modifier = Modifier.align(Alignment.TopCenter) ) } } } }

3. 删除com.jetbrains.spacetutorial包中MainActivity.kt文件的import App行，使setContent()函数引用刚创建的组合函数

4. 在AndroidManifest.xml文件中指定MainActivity类：

   <manifest xmlns:android="http://schemas.android.com/apk/res/android"> ... <application ... <activity ... android:name="com.jetbrains.spacetutorial.MainActivity"> ... </activity> </application> </manifest>

5. 运行Android应用：从运行配置菜单选择composeApp ，选择模拟器后点击运行按钮 应用将自动执行API请求并显示发射列表（背景颜色取决于生成的Material主题）：

   

您已创建了一个业务逻辑在Kotlin跨平台模块中实现，UI使用原生Jetpack Compose构建的Android应用

为SQLDelight添加动态链接标志

默认情况下，Kotlin跨平台向导生成的项目设置为iOS框架的静态链接。

要使用iOS上的原生SQLDelight驱动，需添加允许Xcode工具查找系统提供的SQLite二进制文件的动态链接器标志：

1. 在Android Studio中右键点击iosApp/iosApp.xcodeproj文件夹选择Open In | Xcode

2. 在Xcode中双击项目名称打开设置

3. 切换到Build Settings标签页搜索Other Linker Flags字段

4. 双击字段值点击**+**并添加-lsqlite3字符串

为iOS依赖注入准备Koin类

要在Swift代码中使用Koin类和函数，需创建特殊的KoinComponent类并声明iOS的Koin模块。

1. 在shared/src/iosMain/kotlin/源集创建com/jetbrains/spacetutorial/KoinHelper.kt文件

2. 添加包装SpaceXSDK类并延迟注入Koin的KoinHelper类：

   package com.jetbrains.spacetutorial import org.koin.core.component.KoinComponent import com.jetbrains.spacetutorial.entity.RocketLaunch import org.koin.core.component.inject class KoinHelper : KoinComponent { private val sdk: SpaceXSDK by inject<SpaceXSDK>() suspend fun getLaunches(forceReload: Boolean): List<RocketLaunch> { return sdk.getLaunches(forceReload = forceReload) } }

3. 添加将在Swift中用于初始化和启动iOS Koin模块的initKoin函数：

   import com.jetbrains.spacetutorial.cache.IOSDatabaseDriverFactory import com.jetbrains.spacetutorial.network.SpaceXApi import org.koin.core.context.startKoin import org.koin.dsl.module fun initKoin() { startKoin { modules(module { single<SpaceXApi> { SpaceXApi() } single<SpaceXSDK> { SpaceXSDK( databaseDriverFactory = IOSDatabaseDriverFactory(), api = get() ) } }) } }

现在可以在iOS应用中启动Koin模块，将原生数据库驱动与通用的SpaceXSDK类结合使用

实现UI

首先创建用于显示列表项的RocketLaunchRow SwiftUI视图。它将基于`H