Android Room使用
文章目录
- Room
-
- 概述
- 使用
-
- API说明
- 配置数据库
- 增加数据
- 删除数据
- 修改数据
- 查询数据
- 事务
- Room高级用法
-
- 嵌套对象
- 一对一
- 一对多
- 数据库升级
-
- 新增表
- 新增表字段
- 源码下载
Room
概述
- Google推出的Jetpack组件之一
- 功能强大，使用简单，支持数据库监听等
添加依赖
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'
...
dependencies {
//Room
implementation "androidx.room:room-runtime:2.3.0"
kapt "androidx.room:room-compiler:2.3.0"
//Kotlin支持库
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.2"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.2"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-jdk8:1.4.3"
}
使用
API说明
- Entity：定义数据库中的表，每个实体类对应数据库中的一张表
- Dao：访问数据库的方法，对数据库的各项操作进行封装
- Database：定义数据库，如：数据库版本号、表
- Room数据库相关操作必须在子线程中执行
配置数据库
定义Entity类
@Entity
data class User(var firstName: String, var lastName: String, var age: Int) {
@PrimaryKey(autoGenerate = true)
var id: Long = 0
}
定义Dao类
@Dao
interface UserDao {
@Insert
fun insertUser(user: User)
@Insert
fun insertAllUser(user: List<User>)
@Update
fun updateUser(newUser: User)
@Query("update User set age=100 where age= :age")
fun updateUserWithAge(age: Int)
@Query("select * from User")
fun queryAllUsers(): List<User>
@Query("select * from User where age >= :age")
fun queryUserByAge(age: Int): List<User>
@Delete
fun deleteUser(user: User)
@Query("delete from User where age = :age")
fun deleteUserByAge(age: Int): Int
}
定义Database类
@Database(version = 1, entities = [User::class])
abstract class MyRoomDatabase : RoomDatabase() {
companion object {
private var instance: MyRoomDatabase? = null
private const val DB_NAME = "myroom"
@Synchronized
fun getDatabase(context: Context): MyRoomDatabase {
instance?.let {
return it
}
return Room.databaseBuilder(
context.applicationContext,
MyRoomDatabase::class.java,
DB_NAME
).build().apply {
instance = this
}
}
}
abstract fun userDao(): UserDao
}
初始化操作
userDao = MyRoomDatabase.getDatabase(this).userDao()
增加数据
增加一条数据
val user = User("小", "明", 18)
userDao.insertUser(user)
增加多条数据
val userList =
arrayListOf<User>(
User("小", "白", 18),
User("小", "黑", 28),
User("大", "白", 38),
User("大", "黑", 48)
)
userDao.insertAllUser(userList)
删除数据
删除条件数据
userDao.deleteUserByAge(28)
修改数据
修改条件数据
userDao.updateUserWithAge(48)
修改数据根据主键
val userList = userDao.queryUserByAge(20)
for (user in userList) {
user.age = 1000
userDao.updateUser(user)
}
查询数据
查询所有数据
val userList = userDao.queryAllUsers()
查询条件数据
val userList = userDao.queryUserByAge(20)
事务
//方式一
//使用注解
@Transaction
private fun transaction1() {
thread {
userDao.insertUser(User("李", "四", 28))
userDao.insertUser(User("张", "三", 18))
userDao.deleteUserByAge(28)
}
}
//方式二
//使用runInTransaction
private fun transaction2() {
thread {
MyRoomDatabase.getDatabase(this).runInTransaction {
userDao.insertUser(User("李", "四", 28))
userDao.insertUser(User("张", "三", 18))
userDao.deleteUserByAge(28)
}
}
}
Room高级用法
嵌套对象
data class Address(var addr: String?, var detailAddress: String?)
@Entity
data class Consumer(
var name: String,
var age: Int,
@Embedded
var address: Address? = null
) {
@PrimaryKey(autoGenerate = true)
var id: Long = 0L
}
注：最终Consumer表中一共有：id、name、age、addr、detailAddress字段
一对一
//Entity
@Entity
data class Consumer(
var name: String,
var age: Int,
@Embedded
var address: Address? = null
) {
@PrimaryKey(autoGenerate = true)
var id: Long = 0L
}
@Entity
data class Library(
var libraryName: String,
var consumerId: Long
) {
@PrimaryKey(autoGenerate = true)
var libraryId: Long = 0L
}
//一对一关联类
data class ConsumerAndLibrary(
@Embedded
var consumer: Consumer,
@Relation(parentColumn = "id", entityColumn = "consumerId")
var library: Library
)
//Dao
//一对一查询
@Transaction
@Query("SELECT * FROM Consumer")
fun getConsumerAndLibraryList(): List<ConsumerAndLibrary>
查询操作：
val consumerAndLibraryList =
MyRoomDatabase.getDatabase(this).libraryDao().getConsumerAndLibraryList()
for (i in consumerAndLibraryList) {
log(i)
}
ConsumerAndLibrary(consumer=Consumer(name=小明, age=18, address=null), library=Library(libraryName=歌曲4, consumerId=1))
ConsumerAndLibrary(consumer=Consumer(name=小黑, age=28, address=null), library=Library(libraryName=歌曲5, consumerId=2))
ConsumerAndLibrary(consumer=Consumer(name=小白, age=38, address=null), library=Library(libraryName=歌曲6, consumerId=3))
一对多
//一对多关联
data class ConsumerAndLibrarys(
@Embedded
var consumer: Consumer,
@Relation(parentColumn = "id", entityColumn = "consumerId")
var library: List<Library>
)
//Dao
//一对多查询
@Transaction
@Query("SELECT * FROM Consumer")
fun getConsumerAndLibrarysList(): List<ConsumerAndLibrarys>
查询操作：
val consumerAndLibrarysList =
MyRoomDatabase.getDatabase(this).libraryDao().getConsumerAndLibrarysList()
for (i in consumerAndLibrarysList) {
log(i)
}
ConsumerAndLibrarys(consumer=Consumer(name=小明, age=18, address=null), library=[Library(libraryName=歌曲1, consumerId=1), Library(libraryName=歌曲4, consumerId=1)])
ConsumerAndLibrarys(consumer=Consumer(name=小黑, age=28, address=null), library=[Library(libraryName=歌曲2, consumerId=2), Library(libraryName=歌曲5, consumerId=2)])
ConsumerAndLibrarys(consumer=Consumer(name=小白, age=38, address=null), library=[Library(libraryName=歌曲3, consumerId=3), Library(libraryName=歌曲6, consumerId=3)])
数据库升级
- Room会触发所有迁移策略，一个接着一个执行
新增表
新建Entity类
@Entity
data class Book(var name: String, var pages: Int) {
@PrimaryKey(autoGenerate = true)
var id = 0L
}
配置升级信息
private const val DB_NAME = "myroom"
private const val DB_VERSION = 2
@Database(version = DB_VERSION, entities = [User::class, Book::class])
abstract class MyRoomDatabase : RoomDatabase() {
companion object {
private var instance: MyRoomDatabase? = null
//版本1升级到版本2策略
private val updateVersion_1_2 = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
val sql =
"create table Book(id integer primary key autoincrement not null, name text not null, pages integer not null)"
database.execSQL(sql)
}
}
@Synchronized
fun getDatabase(context: Context): MyRoomDatabase {
instance?.let {
return it
}
return Room.databaseBuilder(
context.applicationContext,
MyRoomDatabase::class.java,
DB_NAME
)
.addMigrations(updateVersion_1_2)
.build().apply {
instance = this
}
}
}
}
新增表字段
修改配置类
private const val DB_NAME = "myroom"
private const val DB_VERSION = 3
@Database(version = DB_VERSION, entities = [User::class, Book::class])
abstract class MyRoomDatabase : RoomDatabase() {
companion object {
private var instance: MyRoomDatabase? = null
//版本1升级到版本2策略
private val updateVersion_1_2 = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
val sql =
"create table Book(id integer primary key autoincrement not null, name text not null, pages integer not null)"
database.execSQL(sql)
}
}
//版本2升级到版本3
private val updateVersion_2_3 = object : Migration(2, 3) {
override fun migrate(database: SupportSQLiteDatabase) {
val sql = "alter table Book add column info text not null default 'unknown'"
database.execSQL(sql)
}
}
@Synchronized
fun getDatabase(context: Context): MyRoomDatabase {
instance?.let {
return it
}
return Room.databaseBuilder(
context.applicationContext,
MyRoomDatabase::class.java,
DB_NAME
)
.addMigrations(updateVersion_1_2, updateVersion_2_3)
.build().apply {
instance = this
}
}
}
}
修改Entity类
@Entity
data class Book(var name: String, var pages: Int, var info: String) {
@PrimaryKey(autoGenerate = true)
var id = 0L
}