jetpack compose 在service里面使用room和数据库交互

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theme: vuepress

在 Jetpack Compose 中使用 Room 和 Service 进行数据库交互是完全可行的。下面是一个示例，演示如何在 Service 中使用 Room 数据库，并通过 Jetpack Compose 来展示数据。

步骤1：设置 Room 数据库

首先，我们需要创建一个 Room 数据库。假设我们有一个简单的 User 实体。

// User.kt
import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity(tableName = "user_table")
data class User(
    @PrimaryKey(autoGenerate = true) val id: Int = 0,
    val name: String
)

然后，创建一个 DAO 接口。

// UserDao.kt
import androidx.room.Dao
import androidx.room.Insert
import androidx.room.Query

@Dao
interface UserDao {
    @Insert
    suspend fun insert(user: User)

    @Query("SELECT * FROM user_table")
    suspend fun getAllUsers(): List<User>
}

接着，创建数据库类。

// AppDatabase.kt
import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase

@Database(entities = [User::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
    abstract fun userDao(): UserDao

    companion object {
        @Volatile
        private var INSTANCE: AppDatabase? = null

        fun getDatabase(context: Context): AppDatabase {
            return INSTANCE ?: synchronized(this) {
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    AppDatabase::class.java,
                    "app_database"
                ).build()
                INSTANCE = instance
                instance
            }
        }
    }
}

步骤2：创建一个 Service 进行数据库操作

接下来，我们创建一个 Service 来进行数据库操作。

// UserService.kt
import android.app.Service
import android.content.Intent
import android.os.IBinder
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.launch

class UserService : Service() {
    private lateinit var database: AppDatabase
    private val serviceScope = CoroutineScope(Job() + Dispatchers.IO)

    override fun onCreate() {
        super.onCreate()
        database = AppDatabase.getDatabase(this)
    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        val action = intent?.getStringExtra("ACTION")
        when (action) {
            "INSERT" -> {
                val name = intent.getStringExtra("NAME") ?: return START_NOT_STICKY
                insertUser(name)
            }
        }
        return START_NOT_STICKY
    }

    private fun insertUser(name: String) {
        serviceScope.launch {
            val user = User(name = name)
            database.userDao().insert(user)
        }
    }

    override fun onBind(intent: Intent?): IBinder? {
        return null
    }
}

步骤3：在 Jetpack Compose 中展示数据

最后，我们使用 Jetpack Compose 来展示从数据库中读取的数据。

// MainActivity.kt
import android.content.Intent
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.lazy.LazyColumn
import androidx.compose.foundation.lazy.items
import androidx.compose.material3.*
import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.lifecycle.lifecycleScope
import kotlinx.coroutines.launch

class MainActivity : ComponentActivity() {
    private lateinit var database: AppDatabase

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        database = AppDatabase.getDatabase(this)

        setContent {
            MyApp()
        }

        lifecycleScope.launch {
            database.userDao().insert(User(name = "John Doe"))
        }
    }

    @Composable
    fun MyApp() {
        var users by remember { mutableStateOf(listOf<User>()) }

        LaunchedEffect(Unit) {
            users = database.userDao().getAllUsers()
        }

        MaterialTheme {
            Surface(modifier = Modifier.fillMaxSize()) {
                Column {
                    Button(onClick = { 
                        startService(Intent(this@MainActivity, UserService::class.java).apply {
                            putExtra("ACTION", "INSERT")
                            putExtra("NAME", "Jane Doe")
                        })
                    }) {
                        Text(text = "Add User")
                    }

                    LazyColumn {
                        items(users) { user ->
                            Text(text = user.name)
                        }
                    }
                }
            }
        }
    }
}