使用 Jetpack Compose、Room 和 ViewModel 实现设置信息持久化并自动更新 UI

以下是使用 Jetpack Compose、Room 和 ViewModel 实现设置信息持久化并自动更新 UI 的步骤：

一、创建 Room 数据库相关部分

1. 定义实体类：

import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity(tableName = "settings")
data class SettingEntity(
    @PrimaryKey(autoGenerate = true) val id: Int = 0,
    val settingName: String,
    val settingValue: String
)

2. 创建 DAO：

import androidx.room.Dao
import androidx.room.Insert
import androidx.room.Query

@Dao
interface SettingDao {
    @Insert
    suspend fun insertSetting(setting: SettingEntity)

    @Query("SELECT * FROM settings WHERE settingName = :name")
    suspend fun getSettingByName(name: String): SettingEntity?
}

3. 创建数据库：

import androidx.room.Database
import androidx.room.RoomDatabase

@Database(entities = [SettingEntity::class], version = 1)
abstract class AppDatabase : RoomDatabase() {
    abstract fun settingDao(): SettingDao
}

二、创建 ViewModel

1. 定义 ViewModel 类：

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.launch

class SettingsViewModel : ViewModel() {
    private val _appName = MutableStateFlow<String?>(null)
    val appName: StateFlow<String?> = _appName

    private val _dayNightMode = MutableStateFlow<String?>(null)
    val dayNightMode: StateFlow<String?> = _dayNightMode

    fun loadAppNameFromDatabase(db: AppDatabase) {
        viewModelScope.launch {
            val setting = db.settingDao().getSettingByName("softwareName")
            _appName.value = setting?.settingValue
        }
    }

    fun saveAppNameToDatabase(db: AppDatabase, appName: String) {
        viewModelScope.launch {
            val existingSetting = db.settingDao().getSettingByName("softwareName")
            if (existingSetting == null) {
                db.settingDao().insertSetting(SettingEntity(settingName = "softwareName", settingValue = appName))
            } else {
                existingSetting.settingValue = appName
                db.settingDao().insertSetting(existingSetting)
            }
            _appName.value = appName
        }
    }

    fun loadDayNightModeFromDatabase(db: AppDatabase) {
        viewModelScope.launch {
            val setting = db.settingDao().getSettingByName("softwareDayNigh")
            _dayNightMode.value = setting?.settingValue
        }
    }

    fun saveDayNightModeToDatabase(db: AppDatabase, mode: String) {
        viewModelScope.launch {
            val existingSetting = db.settingDao().getSettingByName("softwareDayNigh")
            if (existingSetting == null) {
                db.settingDao().insertSetting(SettingEntity(settingName = "softwareDayNigh", settingValue = mode))
            } else {
                existingSetting.settingValue = mode
                db.settingDao().insertSetting(existingSetting)
            }
            _dayNightMode.value = mode
        }
    }
}

三、在 Jetpack Compose 中使用

1. 软件名称配置页面：

import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.material.Button
import androidx.compose.material.Text
import androidx.compose.material.TextField
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext

@Composable
fun SoftwareNameSettingsPage() {
    val db = rememberDatabase()
    val viewModel = remember { SettingsViewModel() }
    var appName by remember { mutableStateOf("") }

    LaunchedEffect(Unit) {
        viewModel.loadAppNameFromDatabase(db)
    }

    LaunchedEffect(viewModel.appName) {
        viewModel.appName.value?.let {
            appName = it
        }
    }

    Column(
        modifier = Modifier
           .fillMaxWidth()
           .padding(16.dp)
    ) {
        TextField(
            value = appName,
            onValueChange = {
                appName = it
            },
            label = { Text("软件名称") },
            modifier = Modifier.fillMaxWidth()
        )
        Button(
            onClick = {
                launch {
                    viewModel.saveAppNameToDatabase(db, appName)
                }
            },
            modifier = Modifier.padding(top = 16.dp)
        ) {
            Text("保存")
        }
    }
}

private fun rememberDatabase(): AppDatabase {
    return androidx.room.Room.databaseBuilder(
        LocalContext.current,
        AppDatabase::class.java,
        "app_database"
    ).build()
}

2. 软件白天黑夜模式配置页面：

import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.material.Button
import androidx.compose.material.RadioButton
import androidx.compose.material.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.unit.dp
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext

@Composable
fun DayNightModeSettingsPage() {
    val db = rememberDatabase()
    val viewModel = remember { SettingsViewModel() }
    var selectedMode by remember { mutableStateOf("") }

    LaunchedEffect(Unit) {
        viewModel.loadDayNightModeFromDatabase(db)
    }

    LaunchedEffect(viewModel.dayNightMode) {
        viewModel.dayNightMode.value?.let {
            selectedMode = it
        }
    }

    Column(
        modifier = Modifier
           .fillMaxWidth()
           .padding(16.dp)
    ) {
        Text("选择白天黑夜模式：")
        RadioButton(
            selected = selectedMode == "light",
            onClick = { selectedMode = "light" },
            modifier = Modifier.padding(top = 8.dp)
        ) {
            Text("白天模式")
        }
        RadioButton(
            selected = selectedMode == "dark",
            onClick = { selectedMode = "dark" },
            modifier = Modifier.padding(top = 8.dp)
        ) {
            Text("黑夜模式")
        }
        Button(
            onClick = {
                launch {
                    viewModel.saveDayNightModeToDatabase(db, selectedMode)
                }
            },
            modifier = Modifier.padding(top = 16.dp)
        ) {
            Text("保存")
        }
    }
}

private fun rememberDatabase(): AppDatabase {
    return androidx.room.Room.databaseBuilder(
        LocalContext.current,
        AppDatabase::class.java,
        "app_database"
    ).build()
}

这样，在不同的页面可以分别配置软件名称和白天黑夜模式，并且数据库的更改会自动反映到 UI 上。