我用的是
RoomDatabase.Callback
在以下情况下填充数据库:
onCreate
被调用。根据文档,只应调用此方法
一旦
第一次创建数据库时。
第一次创建数据库时调用。这个叫
在创建所有表之后。
但出于某种原因,它被称为两次(有时超过两次)。如果在第二次调用中替换了数据,这不会是一个太大的问题,但是因为每个调用都用单独的输入调用启动一个新线程,所以它正在创建重复的数据。
这是有问题的数据库。
@Database(entities = [FTSPlaceholder::class], version = 1)
abstract class DirectoryDatabase : RoomDatabase() {
companion object {
const val NAME = "directory_database"
@Volatile private var INSTANCE: DirectoryDatabase? = null
fun getInstance(context: Context): DirectoryDatabase = INSTANCE ?: synchronized(this) {
INSTANCE ?: buildDatabase(context).also { INSTANCE = it }
}
private fun buildDatabase(context: Context): DirectoryDatabase =
Room.databaseBuilder(context.applicationContext, DirectoryDatabase::class.java, NAME)
.addCallback(FTSCallback()).build()
}
fun addCallback(callback: Callback) {
if (mCallbacks == null) mCallbacks = ArrayList()
mCallbacks?.add(callback)
}
abstract fun departmentDao(): DepartmentDao
abstract fun employeeDao(): EmployeeDao
private class FTSCallback : Callback() {
companion object {
private const val CREATE_TABLE_DEPARTMENTS =
"CREATE VIRTUAL TABLE IF NOT EXISTS `departments` " +
"USING FTS4(`code` TEXT NOT NULL, `title` TEXT NOT NULL, " +
"`location` TEXT NOT NULL, `phone` TEXT, `fax` TEXT, PRIMARY KEY(`code`))"
private const val CREATE_TABLE_PERSONNEL =
"CREATE VIRTUAL TABLE IF NOT EXISTS `personnel` " +
"USING FTS4(`familyName` TEXT NOT NULL, `givenName` TEXT NOT NULL, " +
"`middleName` TEXT, `title` TEXT NOT NULL, `location` TEXT NOT NULL, " +
"`room` TEXT NOT NULL, `phone1` TEXT NOT NULL, `phone2` TEXT NOT NULL, " +
"`email` TEXT NOT NULL, `fax` TEXT, `department` TEXT NOT NULL, " +
"`school` TEXT, PRIMARY KEY(`familyName`, `givenName`, `title`))"
}
override fun onCreate(db: SupportSQLiteDatabase) {
db.execSQL(CREATE_TABLE_DEPARTMENTS)
db.execSQL(CREATE_TABLE_PERSONNEL)
}
}
}
我做了一些奇怪的事情来增加FTS支持,但这不应该导致
onCreate()
被调用两次;特别是考虑到我在另一个数据库中做同样的事情,这不会引起相同的问题。
@Database(entities = [Area::class], version = 1)
abstract class MapDatabase : RoomDatabase() {
companion object {
const val NAME = "map_database"
@Volatile private var INSTANCE: MapDatabase? = null
fun getInstance(context: Context): MapDatabase = INSTANCE ?: synchronized(this) {
INSTANCE ?: buildDatabase(context).also { INSTANCE = it }
}
private fun buildDatabase(context: Context): MapDatabase =
Room.databaseBuilder(context.applicationContext, MapDatabase::class.java, NAME)
.addCallback(FTSCallback()).build()
}
fun addCallback(callback: Callback) {
if (mCallbacks == null) mCallbacks = ArrayList()
mCallbacks?.add(callback)
}
abstract fun placeDao(): PlaceDao
abstract fun areaDao(): AreaDao
private class FTSCallback : Callback() {
companion object {
private const val CREATE_TABLE_PLACES =
"CREATE VIRTUAL TABLE IF NOT EXISTS `places` " +
"USING FTS4(`id` INTEGER NOT NULL, `title` TEXT NOT NULL, " +
"`subtitle` TEXT, `description` TEXT, `latitude` REAL NOT NULL, " +
"`longitude` REAL NOT NULL, `type` INTEGER NOT NULL, " +
"`parent` INTEGER, PRIMARY KEY(`id`))"
}
override fun onCreate(db: SupportSQLiteDatabase) {
db.execSQL(CREATE_TABLE_PLACES)
}
}
}
我将回调添加到单独的存储库类中的数据库中。
class DirectoryRepository(application: Application) {
private val database = DirectoryDatabase.getInstance(application)
init {
database.addCallback(object : RoomDatabase.Callback() {
// This method is being called twice
override fun onCreate(db: SupportSQLiteDatabase) {
refresh()
}
}
}
// Code omitted for brevity
}
我不明白为什么会发生这种情况,特别是考虑到它只发生在我的两个(非常相似)实现中的一个。
