Room

Room是Google為了簡化舊版的SQLite操作專門提供的
1.擁有了SQLite的所有操作功能
2.使用簡單（類似於Retrofit），通過註解的方式實現相關功能。編譯時自動生成實現類impl
3.LiveData，LifeCycle，Paging天然融合支援

匯入

...

plugins {
  id 'com.android.application'
  id 'kotlin-android'
  id 'kotlin-android-extensions'
  id 'kotlin-kapt'
}

dependencies {
  //room資料庫
  implementation "androidx.room:room-runtime:2.2.5"
  kapt "androidx.room:room-compiler:2.2.5" // Kotlin 使用 kapt
  implementation "androidx.room:room-ktx:2.2.5"//Coroutines support for Room 協程操作庫

  //lifecycle
  implementation 'androidx.lifecycle:lifecycle-extensions:2.2.0'
  implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.2.0'
}

User

package com.zhangyu.myroom.data

import android.os.Parcelable
import androidx.room.Entity
import androidx.room.PrimaryKey
import kotlinx.android.parcel.Parcelize

@Parcelize
@Entity(tableName = "User")
data class User(
  @PrimaryKey
  var id: String,var name: String
) : Parcelable

UserDao

package com.zhangyu.myroom.data

import androidx.room.*

@Dao
interface UserDao {

  @Insert(onConflict = OnConflictStrategy.REPLACE)
  fun putUser(cacheBean: User)

  @Query("select * from User where id =:id")
  suspend fun getUser(id: String): User?

  @Query("select * from User")
  suspend fun getAllUser(): List<User>?

  @Delete
  fun delete(user: User)

  @Update(onConflict = OnConflictStrategy.REPLACE)
  fun update(user: User)

}

UserDatabase

package com.zhangyu.myroom.data

import android.util.Log
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase
import androidx.sqlite.db.SupportSQLiteDatabase
import com.zhangyu.myroom.App

private const val TAG = "CacheDataBase"

//後續的資料庫升級是根據這個version來比較的，exportSchema匯出架構
@Database(entities = [User::class],version = 1,exportSchema = false)
abstract class UserDatabase : RoomDatabase() {
  companion object {
    var dataBase: UserDatabase

    init {
      //如果databaseBuilder改為inMemoryDatabaseBuilder則建立一個記憶體資料庫（程序銷燬後，資料丟失）
      dataBase = Room.databaseBuilder(App.context,UserDatabase::class.java,"db_user")
        //是否允許在主執行緒進行查詢
        .allowMainThreadQueries()
        //資料庫建立和開啟後的回撥，可以重寫其中的方法
        .addCallback(object : Callback() {
          override fun onCreate(db: SupportSQLiteDatabase) {
            super.onCreate(db)
            Log.d(TAG,"onCreate: db_user")
          }
        })
        //資料庫升級異常之後的回滾
        .fallbackToDestructiveMigration()
        .build()
    }

  }

  abstract fun getUserDao(): UserDao
}

MainActivity

package com.zhangyu.myroom

import android.os.Bundle
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import androidx.lifecycle.lifecycleScope
import com.zhangyu.myroom.data.User
import com.zhangyu.myroom.data.UserDatabase
import kotlinx.coroutines.launch

private const val TAG = "MainActivity"

class MainActivity : AppCompatActivity() {

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    testCache()
  }

  private fun testCache() {
    val userDao = UserDatabase.dataBase.getUserDao()
    userDao.putUser(User("1001","zhangyu"))
    userDao.putUser(User("1002","liming"))

    lifecycleScope.launch {
      val users = userDao.getAllUser()
      Log.e(TAG,"users: $users")
      val user = userDao.getUser("1001")
      Log.e(TAG,"user: $user")
      Log.e(TAG,"testCache: 協程執行完畢")
    }

    Log.e(TAG,"testCache: ")

  }
}

結果

E/MainActivity: testCache:
E/MainActivity: users: [User(id=1001,name=zhangyu),User(id=1002,name=liming)]
E/MainActivity: user: User(id=1001,name=zhangyu)
E/MainActivity: testCache: 協程執行完畢

到此這篇關於Android kotlin+協程+Room資料庫的簡單使用的文章就介紹到這了,更多相關Android kotlin協程使用內容請搜尋我們以前的文章或繼續瀏覽下面的相關文章希望大家以後多多支援我們！