Simple Use of Android kotlin + Synergetic + Room Database

Room

Room is specially provided by Google to simplify the operation of the older version of SQLite
1. Have all the operation functions of SQLite
2. It is easy to use (similar to Retrofit), and related functions are realized by annotation. Automatically generate the implementation class impl at compile time
3. Natural fusion support of LiveData, LifeCycle and Paging

Import

...

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

dependencies {
  //room Database 
  implementation "androidx.room:room-runtime:2.2.5"
  kapt "androidx.room:room-compiler:2.2.5" // Kotlin  Use  kapt
  implementation "androidx.room:room-ktx:2.2.5"//Coroutines support for Room  Synergetic operation library 

  //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"

// Subsequent database upgrades are based on this version To compare, exportSchema Export schema 
@Database(entities = [User::class], version = 1, exportSchema = false)
abstract class UserDatabase : RoomDatabase() {
  companion object {
    var dataBase: UserDatabase

    init {
      // If databaseBuilder Replace with inMemoryDatabaseBuilder Is created 1 Main memory database (data lost after process destruction) 
      dataBase = Room.databaseBuilder(App.context, UserDatabase::class.java, "db_user")
        // Whether to allow queries on the main thread 
        .allowMainThreadQueries()
        // Callbacks after the database is created and opened, which can override the methods in it 
        .addCallback(object : Callback() {
          override fun onCreate(db: SupportSQLiteDatabase) {
            super.onCreate(db)
            Log.d(TAG, "onCreate: db_user")
          }
        })
        // Rollback after database upgrade exception 
        .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:  Complete the execution of the coordination process ")
    }

    Log.e(TAG, "testCache: ")

  }
}

Results

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: Co-execution completed