Android数据库组件Room
Room是Android官方提供的sqlite数据库管理组件。
添加依赖
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'
android {
...
defaultConfig {
...
javaCompileOptions {
annotationProcessorOptions {
arguments = ["room.schemaLocation": "$projectDir/build/room/schemas".toString()]
}
}
}
...
}
dependencies {
...
def room_version = "1.1.1"
implementation "android.arch.persistence.room:runtime:$room_version"
kapt "android.arch.persistence.room:compiler:$room_version"
implementation "android.arch.persistence.room:rxjava2:$room_version"
implementation "android.arch.persistence.room:guava:$room_version"
testImplementation "android.arch.persistence.room:testing:$room_version"
}创建数据库
val accountDB: AccountDB = Room.databaseBuilder(context, AccountDB::class.java, "account.db")
.allowMainThreadQueries()//允许在主线程查询（如果不允许主线程查询，可以使用LiveData）
.fallbackToDestructiveMigration()//数据库版本更新，清空数据库
.addMigrations(migration_1_2)//数据库版本更新，修改数据库
.build()@Database(entities = [User::class, Phone::class], version = 1)
abstract class AccountDB : RoomDatabase() {
abstract fun userDao(): UserDao
abstract fun phoneDao(): PhoneDao
}定义实体表
@Entity(tableName = "user")
class User {
@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "id")
var id: Long = 0
@ColumnInfo(name = "nickname")
var nickname: String = ""
@ColumnInfo(name = "birthday")
var birthday: Long = 0
@Ignore
var picture: Bitmap? = null
}@Entity(tableName = "phone")
class Phone {
@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "id")
var id: Long = 0
@ColumnInfo(name = "num")
var num: String = ""
@ColumnInfo(name = "userId")
var userId: Long = 0
}Dao类
@Dao
interface UserDao {
@Query("SELECT * FROM user")
fun query(): List
@Query("SELECT * FROM user")
fun queryLiveData(): LiveData>
@Query("SELECT * FROM user WHERE id IN (:userIds)")
fun queryByIds(vararg userIds: Int): List
@Query("SELECT * FROM user WHERE nickname LIKE :nickname")
fun queryByNickname(nickname: String): List
@Insert
fun insert(user: User):Long
@Update
fun update(user: User):Int
@Delete
fun delete(user: User):Int
@Transaction
@Query("SELECT * FROM user")
fun queryUserAndPhone(): List
} @Dao
interface PhoneDao {
@Insert
fun insert(phone: Phone):Long
}数据库查询
val accountDB = Room.databaseBuilder(App.context, AccountDB::class.java, "account.db")
.allowMainThreadQueries()
.build()
val user = User()
accountDB.userDao().insert(user)//新增
accountDB.userDao().query()//查询
accountDB.userDao().update(user)//修改
accountDB.userDao().delete(user)//删除事务处理
val accountDB = Room.databaseBuilder(App.context, AccountDB::class.java, "account.db")
.allowMainThreadQueries()
.build()
try {
//执行事务
accountDB.runInTransaction {
val user = User()
//插入数据
DBUtil.accountDB.userDao().insert(user)
"a".toInt()//异常
}
} catch (e: Exception) {
e.printStackTrace()
Toast.makeText(this, "异常，数据回滚", Toast.LENGTH_SHORT).show()
}LiveData查询
val accountDB = Room.databaseBuilder(App.context, AccountDB::class.java, "account.db")
.allowMainThreadQueries()
.build()
accountDB.userDao().queryLiveData().observe(this, Observer {list->
log(list.toString())
})关联查询
class UserAndPhone {
@Embedded
var user: User = User()
@Relation(parentColumn = "id", entityColumn = "userId")
var phoneList: List = ArrayList()
override fun toString(): String {
return "UserAndPhone(user=$user, phoneList=$phoneList)"
}
} @Dao
interface UserDao {
@Transaction
@Query("SELECT * FROM user")
fun queryUserAndPhone(): List
} 数据库版本更新
val migration_1_2: Migration = object : Migration(1, 2) {
override fun migrate(database: SupportSQLiteDatabase) {
database.execSQL("ALTER TABLE user ADD birthday INTEGER NOT NULL DEFAULT 0")
}
}
val accountDB = Room.databaseBuilder(App.context, AccountDB::class.java, "account.db")
.allowMainThreadQueries()
.addMigrations(migration_1_2)
.build()RoomDemo：https://github.com/dingjianlun/RoomDemo