Кое-что добавил

app/src/main/java/com/example/mobileapp/database/MobileAppDataBase.kt

@@ -1,11 +1,53 @@
 package com.example.mobileapp.database
 
+import android.content.Context
 import androidx.room.Database
+import androidx.room.Room
 import androidx.room.RoomDatabase
+import androidx.room.TypeConverters
+import androidx.sqlite.db.SupportSQLiteDatabase
+import com.example.mobileapp.database.dao.MailDao
+import com.example.mobileapp.database.dao.StoryDao
+import com.example.mobileapp.database.dao.UserDao
+import com.example.mobileapp.database.entities.Converters
 import com.example.mobileapp.database.entities.Mail
 import com.example.mobileapp.database.entities.Story
 import com.example.mobileapp.database.entities.User
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
 
 @Database(entities = [User::class, Story::class, Mail::class], version = 1, exportSchema = false)
+@TypeConverters(Converters::class)
 abstract class MobileAppDataBase : RoomDatabase() {
+    abstract fun userDao(): UserDao
+    abstract fun storyDao(): StoryDao
+    abstract fun mailDao(): MailDao
+
+    companion object{
+        private const val DB_NAME: String = "mobileApp.db"
+
+        @Volatile
+        private var INSTANCE: MobileAppDataBase? = null
+
+        fun getInstance(appContext: Context): MobileAppDataBase {
+            return INSTANCE ?: synchronized(this) {
+                Room.databaseBuilder(
+                    appContext,
+                    MobileAppDataBase::class.java,
+                    DB_NAME
+                )
+                    .addCallback(object : Callback() {
+                        override fun onCreate(db: SupportSQLiteDatabase) {
+                            super.onCreate(db)
+                            CoroutineScope(Dispatchers.IO).launch {
+                                //populateDatabase()
+                            }
+                        }
+                    })
+                    .build()
+                    .also { INSTANCE = it }
+            }
+        }
+    }
 }

app/src/main/java/com/example/mobileapp/database/dao/MailDao.kt

@@ -1,7 +1,11 @@
 package com.example.mobileapp.database.dao
 
 import androidx.room.Dao
+import androidx.room.Delete
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
 import androidx.room.Query
+import androidx.room.Update
 import com.example.mobileapp.database.entities.Mail
 import kotlinx.coroutines.flow.Flow
 
@@ -9,4 +13,16 @@ import kotlinx.coroutines.flow.Flow
 interface MailDao {
     @Query("select * from mails")
     fun getAll(): Flow<List<Mail>>
+
+    @Query("select * from mails where mails.id = :id")
+    fun getById(id: Int): Mail?
+
+    @Insert(onConflict = OnConflictStrategy.IGNORE)
+    suspend fun insert(mail: Mail)
+
+    @Update
+    suspend fun update(mail: Mail)
+
+    @Delete
+    suspend fun delete(mail: Mail)
 }

app/src/main/java/com/example/mobileapp/database/dao/StoryDao.kt

@@ -1,7 +1,11 @@
 package com.example.mobileapp.database.dao
 
 import androidx.room.Dao
+import androidx.room.Delete
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
 import androidx.room.Query
+import androidx.room.Update
 import com.example.mobileapp.database.entities.Story
 import kotlinx.coroutines.flow.Flow
 
@@ -9,4 +13,16 @@ import kotlinx.coroutines.flow.Flow
 interface StoryDao {
     @Query("select * from stories")
     fun getAll(): Flow<List<Story>>
+
+    @Query("select * from stories where stories.id = :id")
+    fun getById(id: Int): Story?
+
+    @Insert(onConflict = OnConflictStrategy.IGNORE)
+    suspend fun insert(story: Story)
+
+    @Update
+    suspend fun update(story: Story)
+
+    @Delete
+    suspend fun delete(story: Story)
 }

app/src/main/java/com/example/mobileapp/database/dao/UserDao.kt

@@ -1,7 +1,11 @@
 package com.example.mobileapp.database.dao
 
 import androidx.room.Dao
+import androidx.room.Delete
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
 import androidx.room.Query
+import androidx.room.Update
 import com.example.mobileapp.database.entities.User
 import kotlinx.coroutines.flow.Flow
 
@@ -9,4 +13,16 @@ import kotlinx.coroutines.flow.Flow
 interface UserDao {
     @Query("select * from users")
     fun getAll():Flow<List<User>>
+
+    @Query("select * from users where users.id = :id")
+    fun getById(id: Int): User?
+
+    @Insert(onConflict = OnConflictStrategy.IGNORE)
+    suspend fun insert(user: User)
+
+    @Update
+    suspend fun update(user: User)
+
+    @Delete
+    suspend fun delete(user: User)
 }

app/src/main/java/com/example/mobileapp/database/entities/Converters.kt

@@ -0,0 +1,20 @@
+package com.example.mobileapp.database.entities
+
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
+import androidx.room.TypeConverter
+import java.io.ByteArrayOutputStream
+
+class Converters {
+    @TypeConverter
+    fun fromBitmap(bitmap: Bitmap) : ByteArray {
+        val outputStream = ByteArrayOutputStream();
+        bitmap.compress(Bitmap.CompressFormat.PNG, 100, outputStream)
+        return outputStream.toByteArray()
+    }
+
+    @TypeConverter
+    fun toBitmap(byteArray: ByteArray): Bitmap {
+        return BitmapFactory.decodeByteArray(byteArray, 0, byteArray.size)
+    }
+}