ImagesDatabase.kt

/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.background.data

import android.content.Context
import androidx.room.Database
import androidx.room.Room
import androidx.room.RoomDatabase

/**
 * This is the backend. The database. This used to be done by the OpenHelper.
 * The fact that this has very few comments emphasizes its coolness.
 */
@Database(entities = [BlurredImage::class], version = 1)
abstract class ImagesDatabase : RoomDatabase() {

    abstract fun blurredImageDao(): BlurredImageDao

    companion object {
        @Volatile
        private var INSTANCE: ImagesDatabase? = null

        fun getDatabase(context: Context): ImagesDatabase {
            // if the INSTANCE is not null, then return it,
            // if it is, then create the database
            return INSTANCE ?: synchronized(this) {
                val instance = Room.databaseBuilder(
                    context.applicationContext,
                    ImagesDatabase::class.java,
                    "images_database"
                ).build()
                INSTANCE = instance
                // return instance
                instance
            }
        }

    }
}