added ability to log out

app/src/main/AndroidManifest.xml

@@ -13,6 +13,7 @@
     <uses-permission android:name="android.permission.READ_MEDIA_VIDEO"/>
     <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE"/>
     <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
 
     <application
             android:allowBackup="true"

app/src/main/java/org/foxarmy/barcodescannerforemployees/Net.kt

@@ -1,5 +1,6 @@
 package org.foxarmy.barcodescannerforemployees
 
+import android.content.Context
 import okhttp3.*
 import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.MediaType.Companion.toMediaTypeOrNull
@@ -17,6 +18,28 @@ class Net {
     var server = "bsfe.foxarmy.org"
     var token = ""
 
+    fun serverIsAvailable(context: Context): Boolean {
+        if (!isInternetConnectionAvailable(context)) {
+            return false
+        }
+        var flag = false
+        thread {
+            val client = OkHttpClient();
+            val request = Request.Builder()
+                .url("https://$server/status")
+                .get()
+                .build();
+
+            try {
+                val response = client.newCall(request).execute();
+                flag =  response.code == 200;
+            } catch (e: Exception) {
+                flag = false;
+            }
+        }.join()
+        return flag
+    }
+
     fun requestProductFromOnlineDB(barcode: String): String {
         var response = ""
         thread {

app/src/main/java/org/foxarmy/barcodescannerforemployees/Parser.kt

@@ -14,8 +14,6 @@ class Parser constructor() {
                 text = text.replace(found, "")
                 netWeight = stripNetWeight(found)
                 return Triple(text, netWeight, found)
-            } else {
-                return Triple(text, 0.0, "")
             }
         }
         return Triple("", 0.0, "")
@@ -48,4 +46,4 @@ class Parser constructor() {
 
         return AbstractProduct(0, "", name, netWeight, "", 0, unitNumber)
     }
-}
+}

app/src/main/java/org/foxarmy/barcodescannerforemployees/Utils.kt

@@ -7,10 +7,15 @@ import android.graphics.Bitmap
 import android.graphics.BitmapFactory
 import android.graphics.Matrix
 import android.media.ExifInterface
+import android.net.ConnectivityManager
+import android.net.NetworkCapabilities
 import android.net.Uri
 import android.os.Build
 import androidx.annotation.RequiresApi
+import androidx.appcompat.app.AlertDialog
 import androidx.core.content.FileProvider
+import androidx.security.crypto.EncryptedSharedPreferences
+import androidx.security.crypto.MasterKeys
 import com.google.firebase.components.BuildConfig
 import java.io.File
 import java.io.FileInputStream
@@ -18,6 +23,7 @@ import java.io.FileOutputStream
 import java.security.MessageDigest
 import java.text.SimpleDateFormat
 import java.util.*
+import kotlin.system.exitProcess
 
 fun convertToUnixEpochTimestamp(dateString: String): Long {
     val format = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'")
@@ -27,7 +33,11 @@ fun convertToUnixEpochTimestamp(dateString: String): Long {
 }
 
 fun getImageUri(activity: Activity, imageFile: File): Uri? {
-    return FileProvider.getUriForFile(activity, BuildConfig.APPLICATION_ID + "." + activity.localClassName + ".provider", imageFile)
+    return FileProvider.getUriForFile(
+        activity,
+        BuildConfig.APPLICATION_ID + "." + activity.localClassName + ".provider",
+        imageFile
+    )
 }
 
 @RequiresApi(Build.VERSION_CODES.R)
@@ -47,13 +57,13 @@ fun generateThumbnailForImage(context: Context, imageHash: String) {
     val orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL)
     val matrix = Matrix()
 
-    when(orientation){
+    when (orientation) {
         ExifInterface.ORIENTATION_ROTATE_90 -> matrix.postRotate(90F)
         ExifInterface.ORIENTATION_ROTATE_180 -> matrix.postRotate(180F)
         ExifInterface.ORIENTATION_ROTATE_270 -> matrix.postRotate(270F)
     }
     val rotated = Bitmap.createBitmap(img, 0, 0, img.width, img.height, matrix, true)
-    val scaled = Bitmap.createScaledBitmap(rotated, rotated.width/4, rotated.height/4, true)
+    val scaled = Bitmap.createScaledBitmap(rotated, rotated.width / 4, rotated.height / 4, true)
     scaled.compress(Bitmap.CompressFormat.WEBP_LOSSY, 25, FileOutputStream(thumbnailFile))
 }
 
@@ -64,8 +74,11 @@ fun String.md5(): String {
     return digest.toHexString()
 }
 
-fun stripNetWeight (netWeight: String): Double {
+fun stripNetWeight(netWeight: String): Double {
-    return removeSubstringsFromString(netWeight, arrayOf("Л", "л", "мл", "Мл", "г", "Г", "кг", "Кг", "шт", "Шт", ",", " ", ".")).toDouble()
+    return removeSubstringsFromString(
+        netWeight,
+        arrayOf("Л", "л", "мл", "Мл", "г", "Г", "кг", "Кг", "шт", "Шт", ",", " ", ".")
+    ).toDouble()
 }
 
 fun removeSubstringsFromString(text: String, toRemove: Array<String>): String {
@@ -99,14 +112,31 @@ fun calculateProductFreshness(dateOfProduction: Long, dateOfExpiry: Long): Doubl
     return lifeSpanLeft / productLifeSpan.toDouble()
 }
 
-fun getUnitNameById (context: Context, id: Int): String {
+fun getUnitNameById(context: Context, id: Int): String {
-    return when(id) {
+    return when (id) {
-        0 -> { context.getString(R.string.kilogram) }
+        0 -> {
-        1 -> { context.getString(R.string.gram) }
+            context.getString(R.string.kilogram)
-        2 -> { context.getString(R.string.liter) }
+        }
-        3 -> { context.getString(R.string.milliliter) }
+
-        4 -> { context.getString(R.string.pieces) }
+        1 -> {
-        else -> { "" }
+            context.getString(R.string.gram)
+        }
+
+        2 -> {
+            context.getString(R.string.liter)
+        }
+
+        3 -> {
+            context.getString(R.string.milliliter)
+        }
+
+        4 -> {
+            context.getString(R.string.pieces)
+        }
+
+        else -> {
+            ""
+        }
     }
 }
 
@@ -137,4 +167,49 @@ fun bytesToHex(bytes: ByteArray): String {
         hexString.append(hex)
     }
     return hexString.toString()
+}
+
+fun isInternetConnectionAvailable(context: Context): Boolean {
+    if (context.getSystemService(Context.CONNECTIVITY_SERVICE) == null) return false
+    val connectivityManager =
+        context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+    if (connectivityManager != null) {
+        val capabilities =
+            connectivityManager.getNetworkCapabilities(connectivityManager.activeNetwork)
+        if (capabilities != null) {
+            if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR)) {
+                return true
+            } else if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI)) {
+                return true
+            } else if (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET)) {
+                return true
+            }
+        }
+    }
+    return false
+}
+
+fun noInternetConnectionAvailableNotification(context: Context) {
+    (context as Activity).runOnUiThread {
+        AlertDialog.Builder(context)
+            .setMessage(context.getString(R.string.no_internet_connection))
+            .setPositiveButton(R.string.quit) { _, _ ->
+                exitProcess(0)
+            }
+            .setNeutralButton(R.string.logout) { _, _ ->
+                val sharedPreferences = EncryptedSharedPreferences.create(
+                    "sensitive",
+                    MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC),
+                    context,
+                    EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+                    EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+                )
+
+                sharedPreferences.edit().putString("token", "").apply()
+                sharedPreferences.edit().putString("server", "").apply()
+                sharedPreferences.edit().putStringSet("groups", emptySet()).apply()
+                sharedPreferences.edit().putString("currentGroup", "").apply()
+                exitProcess(0)
+            }.show()
+    }
 }

app/src/main/java/org/foxarmy/barcodescannerforemployees/WebSocketClient.kt

@@ -0,0 +1,168 @@
+package org.foxarmy.barcodescannerforemployees
+
+import android.content.Context
+import android.os.Build
+import android.util.Log
+import androidx.annotation.RequiresApi
+import okhttp3.*
+import org.foxarmy.barcodescannerforemployees.activities.MainActivity
+import org.foxarmy.barcodescannerforemployees.database.AbstractProductDAO
+import org.foxarmy.barcodescannerforemployees.database.CategoryDAO
+import org.foxarmy.barcodescannerforemployees.database.DBStorageController
+import org.foxarmy.barcodescannerforemployees.database.ProductDAO
+import org.foxarmy.barcodescannerforemployees.dataclasses.AbstractProduct
+import org.foxarmy.barcodescannerforemployees.dataclasses.Category
+import org.foxarmy.barcodescannerforemployees.dataclasses.Product
+import org.json.JSONObject
+import java.io.File
+import java.util.concurrent.TimeUnit
+
+class WebSocketClient(private val context: Context, private val server: String) {
+
+    private lateinit var webSocket: WebSocket
+
+    fun connect(token: String, currentGroup: String) {
+        val client = OkHttpClient.Builder()
+            .connectTimeout(5, TimeUnit.SECONDS)
+            .readTimeout(1, TimeUnit.MINUTES)
+            .writeTimeout(10, TimeUnit.SECONDS)
+            .callTimeout(1, TimeUnit.MINUTES)
+            .build()
+
+        val request = Request.Builder()
+            .url("wss://$server")
+            .build()
+
+        client.newWebSocket(request, object : WebSocketListener() {
+            override fun onOpen(webSocket: WebSocket, response: Response) {
+                this@WebSocketClient.webSocket = webSocket
+                sendMessage("{\"token\":\"$token\",\"currentGroup\":\"$currentGroup\"}")
+                keepAlive()
+            }
+
+            @RequiresApi(Build.VERSION_CODES.O)
+            override fun onMessage(webSocket: WebSocket, text: String) {
+                val payload = JSONObject(text)
+
+                val item = payload["item"] as String
+                val data = payload["data"] as JSONObject
+                val action = payload["action"] as String
+                val currentGroup = payload["groupId"] as String
+
+                val dbHelper = DBStorageController(context, currentGroup)
+                val abstractProductDAO = AbstractProductDAO(dbHelper)
+                val productDAO = ProductDAO(dbHelper)
+                val categoryDAO = CategoryDAO(dbHelper)
+
+                when (action) {
+                    "create" -> {
+                        when (item) {
+                            "abstractproduct" -> {
+                                val newAbstractProduct = AbstractProduct.createFromJSON(data)
+
+                                val net = Net()
+                                net.server = server
+                                net.token = token
+
+                                val picturesDir = File(context.filesDir, "pictures")
+                                picturesDir.mkdirs()
+
+                                val pictureFile =
+                                    File(picturesDir, "${data["image_filename"]}.png")
+                                val url = "https://${net.server}/api/abstractproduct/getImage/${currentGroup}/${data["local_id"]}"
+                                net.downloadImage(url, pictureFile)
+
+                                abstractProductDAO.addAbstractProduct(newAbstractProduct)
+                            }
+
+                            "product" -> {
+                                val newProduct = Product.createFromJSON(data)
+                                productDAO.insertNewProduct(newProduct)
+                            }
+
+                            "category" -> {
+                                val newCategory = Category.createFromJSON(data)
+                                categoryDAO.addCategory(newCategory)
+                            }
+                        }
+                    }
+
+                    "update" -> {
+                        when (item) {
+                            "abstractproduct" -> {
+                                val updatedAbstractProduct = AbstractProduct.createFromJSON(data)
+
+                                val net = Net()
+                                net.server = server
+                                net.token = token
+
+                                val picturesDir = File(context.filesDir, "pictures")
+                                picturesDir.mkdirs()
+
+                                val pictureFile =
+                                    File(picturesDir, "${data["image_filename"]}.png")
+                                val url = "https://${net.server}/api/abstractproduct/getImage/${currentGroup}/${data["local_id"]}"
+                                net.downloadImage(url, pictureFile)
+
+                                abstractProductDAO.updateAbstractProduct(updatedAbstractProduct)
+                            }
+                            "product" -> {
+                                val updatedProduct = Product.createFromJSON(data)
+                                productDAO.updateProduct(updatedProduct)
+                            }
+                            "category" -> {
+                                val updatedCategory = Category.createFromJSON(data)
+                                categoryDAO.updateCategory(updatedCategory)
+                            }
+                        }
+                    }
+
+                    "delete" -> {
+                        val id = data["local_id"] as String
+
+                        when(item) {
+                            "abstractproduct" -> {
+                                abstractProductDAO.eraseAbstractProduct(id.toInt(), context)
+                            }
+                            "product" -> {
+                                productDAO.eraseProduct(id.toInt())
+                            }
+                            "category" -> {
+                                categoryDAO.eraseCategory(id.toInt(), context)
+                            }
+                        }
+                    }
+                }
+
+                (context as MainActivity).updateAll()
+            }
+
+            override fun onClosing(webSocket: WebSocket, code: Int, reason: String) {
+                Log.d("QWERTYUIOP", "Closing ws. Reason: $reason")
+                noInternetConnectionAvailableNotification(context)
+            }
+
+            override fun onFailure(webSocket: WebSocket, t: Throwable, response: Response?) {
+                Log.d("QWERTYUIOP","Connection failed: ${t.message}")
+                noInternetConnectionAvailableNotification(context)
+            }
+        })
+    }
+
+    private fun keepAlive() {
+        Thread {
+            while (true) {
+                Thread.sleep(30000)
+                webSocket.send("keepalive")
+            }
+        }.start()
+    }
+
+    fun sendMessage(message: String) {
+        webSocket.send(message)
+    }
+
+    fun close() {
+        webSocket.close(1000, "Closing WebSocket connection")
+    }
+}

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/AddAbstractProductActivity.kt

@@ -33,6 +33,7 @@ import java.io.FileOutputStream
 import java.nio.file.Files
 import java.nio.file.StandardCopyOption
 import kotlin.concurrent.thread
+import kotlin.math.abs
 
 class AddAbstractProductActivity : AppCompatActivity() {
     private lateinit var imageView: ImageView
@@ -73,7 +74,7 @@ class AddAbstractProductActivity : AppCompatActivity() {
             EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
         )
 
-        val dbHelper = DBStorageController(this, sharedPreferences.getString("currentGroup", "database")!!)
+        val dbHelper = DBStorageController(this, sharedPreferences.getString("currentGroup", "offline")!!)
         DAO = AbstractProductDAO(dbHelper)
 
         picturesPath = File(filesDir, "pictures")
@@ -109,25 +110,28 @@ class AddAbstractProductActivity : AppCompatActivity() {
         action = extras!!.get("action") as String
         when (action) {
             "update" -> {
-                abstractProduct = extras.get("abstractProduct") as AbstractProduct?
+                abstractProduct = extras.get("abstractProduct") as AbstractProduct
             }
 
             "new_from_barcode" -> {
-                abstractProduct = extras.get("abstractProduct") as AbstractProduct?
+                abstractProduct = extras.get("abstractProduct") as AbstractProduct
                 barcode = abstractProduct!!.barcode
                 performRequest(abstractProduct!!.barcode)
             }
         }
 
-        if (abstractProduct != null) {
+        if (abstractProduct != null && action == "update") {
             val imageThumbnailUri = getImageUri(this, File(thumbnailsDir, "${abstractProduct!!.imageHash}.webp"))
-            pictureFile = File(picturesPath, "${abstractProduct!!.imageHash}.png]")
+            pictureFile = File(picturesPath, "${abstractProduct!!.imageHash}.png")
             imageView.setImageURI(imageThumbnailUri)
             barcodeText.setText(abstractProduct!!.barcode)
             productNameText.text = abstractProduct!!.name
             netWeightText.text = abstractProduct!!.netWeight.toString()
-            categorySpinner.setSelection(abstractProduct!!.category)
+            categorySpinner.setSelection(abstractProduct!!.category - 1)
             unitTypeSpinner.setSelection(abstractProduct!!.unit)
+            if (abstractProduct!!.barcode == "" || abstractProduct!!.barcode == "             ") {
+                noBarcodeCheckBox.isChecked = true
+            }
         }
 
         saveButton.setOnClickListener {
@@ -149,20 +153,27 @@ class AddAbstractProductActivity : AppCompatActivity() {
             }
             if (netWeight.toString() == "" || netWeight.toString().toDoubleOrNull() == null) {
                 Toast.makeText(this, getString(R.string.product_net_weight_request), Toast.LENGTH_SHORT).show()
+                return@setOnClickListener
             }
-
+            val currentGroup: Int
-            val net = Net()
+            val currentGroupString = sharedPreferences.getString("currentGroup", "offline")!!
-
-            net.token = sharedPreferences.getString("token", "")!!
-            net.server = sharedPreferences.getString("server", "")!!
-            net.language = sharedPreferences.getString("language", "en-US")!!
-
-            val currentGroup = sharedPreferences.getString("currentGroup", "offline")!!
 
             lateinit var response: Response
+            val net = Net()
+
+            if (currentGroupString != "offline") {
+                currentGroup = currentGroupString.toInt()
+
+                net.token = sharedPreferences.getString("token", "")!!
+                net.server = sharedPreferences.getString("server", "")!!
+                net.language = sharedPreferences.getString("language", "en-US")!!
+
+            } else {
+                currentGroup = 0
+            }
 
             abstractProduct = AbstractProduct(
-                if(abstractProduct == null) 0 else abstractProduct!!.id,
+                if (abstractProduct == null) 0 else abstractProduct!!.id,
                 if (noBarcodeCheckBox.isChecked) "" else barcode,
                 productName,
                 netWeight.toString().toDouble(),
@@ -170,16 +181,18 @@ class AddAbstractProductActivity : AppCompatActivity() {
                 categorySpinner.selectedItemPosition + 1,
                 unitTypeSpinner.selectedItemPosition
             )
+
             val pictureFile = File(File(filesDir, "pictures"), "${abstractProduct!!.imageHash}.png")
 
             if (action == "update") {
                 DAO.updateAbstractProduct(abstractProduct!!)
-                response = net.updateAbstractProduct(currentGroup.toInt(), abstractProduct!!, pictureFile)
+                if (currentGroup > 0) response = net.updateAbstractProduct(currentGroup, abstractProduct!!, pictureFile)
             } else if (action == "new" || action == "new_from_barcode") {
                 abstractProduct!!.id = DAO.addAbstractProduct(abstractProduct!!).toInt()
-                response = net.uploadAbstractProduct(currentGroup.toInt(), abstractProduct!!, pictureFile);
+                if (currentGroup > 0) response =
+                    net.uploadAbstractProduct(currentGroup, abstractProduct!!, pictureFile)
             }
-            Toast.makeText(this, response.body!!.string(), Toast.LENGTH_LONG).show()
+            if (currentGroup > 0) Toast.makeText(this, response.body!!.string(), Toast.LENGTH_LONG).show()
 
             finish()
         }
@@ -198,7 +211,6 @@ class AddAbstractProductActivity : AppCompatActivity() {
         barcodeText.setText(this.barcode)
         val net = Net();
         val result = net.requestProductFromOnlineDB(barcode)
-        Log.d("QWERTYUIOP", "Result of request: $result")
 
         var abstractProduct: AbstractProduct
 
@@ -257,7 +269,8 @@ class AddAbstractProductActivity : AppCompatActivity() {
 
     fun fillupCategorySpinner() {
 
-        val categoriesDAO = CategoryDAO(DBStorageController(this, sharedPreferences.getString("currentGroup", "database")!!))
+        val categoriesDAO =
+            CategoryDAO(DBStorageController(this, sharedPreferences.getString("currentGroup", "database")!!))
 
         val categories = categoriesDAO.getAllCategories().map { category -> category.name }
 
@@ -272,22 +285,15 @@ class AddAbstractProductActivity : AppCompatActivity() {
         if (success) {
             //Move picture to a proper directory according to its calculated hash
             val tempfile = File(filesDir, "image.png")
-            val imageHash = calculateMd5Hash(tempfile)
-//            val imageContent = tempfile.inputStream().readBytes()
-//            val imageHash = imageContent.toString(Charsets.UTF_8).md5()
 
-            pictureFile = File(picturesPath, "$imageHash.png")
+            val imageContent = tempfile.inputStream().readBytes()
-            Files.move(tempfile.toPath(), pictureFile.toPath(), StandardCopyOption.REPLACE_EXISTING)
-            tempfile.delete()
-
-            val imageContent = pictureFile.inputStream().readBytes()
             var img = BitmapFactory.decodeByteArray(imageContent, 0, imageContent.size)
 
-            val exif = ExifInterface(pictureFile.absoluteFile.toString())
+            val exif = ExifInterface(tempfile.absoluteFile.toString())
             val orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL)
             val matrix = Matrix()
 
-            when(orientation){
+            when (orientation) {
                 ExifInterface.ORIENTATION_ROTATE_90 -> matrix.postRotate(90F)
                 ExifInterface.ORIENTATION_ROTATE_180 -> matrix.postRotate(180F)
                 ExifInterface.ORIENTATION_ROTATE_270 -> matrix.postRotate(270F)
@@ -298,9 +304,15 @@ class AddAbstractProductActivity : AppCompatActivity() {
             rotated.compress(
                 Bitmap.CompressFormat.WEBP_LOSSY,
                 100 * (15 / (16 - compressionFactor)),
-                FileOutputStream(pictureFile)
+                FileOutputStream(tempfile)
             )
 
+            val imageHash = calculateMd5Hash(tempfile)
+
+            pictureFile = File(picturesPath, "$imageHash.png")
+            Files.move(tempfile.toPath(), pictureFile.toPath(), StandardCopyOption.REPLACE_EXISTING)
+            tempfile.delete()
+
             generateThumbnailForImage(this, imageHash)
 
             imageView.setImageURI(getImageUri(this, pictureFile))

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/AddCategoryActivity.kt

@@ -48,7 +48,7 @@ class AddCategoryActivity : Activity() {
         net.server = sharedPreferences.getString("server", "")!!
         net.language = sharedPreferences.getString("language", "")!!
 
-        val currentGroup = sharedPreferences.getString("currentGroup", "offline")!!.toInt()
+        val currentGroup: Int = if (sharedPreferences.getString("currentGroup", "offline")!! == "offline") 0 else sharedPreferences.getString("currentGroup", "")!!.toInt()
 
         findViewById<Button>(R.id.saveButton).setOnClickListener {
             if (categoryNameTextEdit.text.toString() == "") {
@@ -59,11 +59,11 @@ class AddCategoryActivity : Activity() {
             if (category.id == 0) { // Inserting new category
                 val newCategory = Category(0, categoryNameTextEdit.text.toString())
                 newCategory.id = DAO.addCategory(newCategory).toInt()
-                net.uploadCategory(currentGroup, newCategory)
+                if (currentGroup > 0) net.uploadCategory(currentGroup, newCategory)
             } else { // Updating existing category
                 category.name = categoryNameTextEdit.text.toString()
                 DAO.updateCategory(category)
-                net.updateCategory(currentGroup, category)
+                if (currentGroup > 0) net.updateCategory(currentGroup, category)
             }
 
             finish()

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/AddProductActivity.kt

@@ -177,7 +177,7 @@ class AddProductActivity : AppCompatActivity() {
                 return@setOnClickListener
             }
 
-            val currentGroup: Int = if (sharedPreferences.getString("currentGroup", "")!! == "") 0 else sharedPreferences.getString("currentGroup", "")!!.toInt()
+            val currentGroup: Int = if (sharedPreferences.getString("currentGroup", "offline")!! == "offline") 0 else sharedPreferences.getString("currentGroup", "")!!.toInt()
 
             var response: Response? = null
 
@@ -200,8 +200,11 @@ class AddProductActivity : AppCompatActivity() {
         val today = SimpleDateFormat("dd.MM.yyyy").format(Calendar.getInstance().time).split(".")
 
 
-        dateOfProductionDatePicker.updateDate(today[2].toInt(), today[1].toInt(), today[0].toInt())
+        dateOfProductionDatePicker.updateDate(today[2].toInt(), today[1].toInt() - 1, today[0].toInt())
-        expiryDatePicker.updateDate(today[2].toInt(), today[1].toInt(), today[0].toInt())
+        expiryDatePicker.updateDate(today[2].toInt(), today[1].toInt() - 1, today[0].toInt())
+        product!!.dateOfProduction = SimpleDateFormat("dd.MM.yyyy").parse("${today[0]}.${today[1]}.${today[2]}")!!.time / 1000
+
+
     }
 
     private val intentLauncher =

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/GroupActivity.kt

@@ -8,6 +8,7 @@ import androidx.security.crypto.EncryptedSharedPreferences
 import androidx.security.crypto.MasterKeys
 import org.foxarmy.barcodescannerforemployees.Net
 import org.foxarmy.barcodescannerforemployees.databinding.ActivityGroupBinding
+import org.foxarmy.barcodescannerforemployees.noInternetConnectionAvailableNotification
 
 class GroupActivity : AppCompatActivity() {
 
@@ -30,25 +31,28 @@ class GroupActivity : AppCompatActivity() {
         binding.createGroupButton.setOnClickListener {
             val groupName = binding.groupNameTextEdit.text.toString()
             val groupPassword = binding.groupPasswordTextEdit.text.toString()
-            // group is set to "successful"
+            val net = Net()
-            val n = Net()
+            net.language = sharedPreferences.getString("language", "en-US")!!
-            n.language = sharedPreferences.getString("language", "en-US")!!
+            net.server = sharedPreferences.getString("server", "")!!
-            n.server = sharedPreferences.getString("server", "")!!
+            net.token = sharedPreferences.getString("token", "")!!
-            n.token = sharedPreferences.getString("token", "")!!
 
-            val response = n.createGroup(groupName, groupPassword)
+            if (!net.serverIsAvailable(this)) {
-            val responseText = response.body!!.string()
+                noInternetConnectionAvailableNotification(this)
-
-            if (response.code == 200) {
-                val currentGroups = sharedPreferences.getStringSet("groups", mutableSetOf())
-                currentGroups!!.add(responseText)
-                sharedPreferences.edit().putStringSet("groups", currentGroups).apply()
-                sharedPreferences.edit().putString("currentGroup", responseText).apply()
-                val intent = Intent(this, MainActivity::class.java)
-                startActivity(intent)
-                finish()
             } else {
-                Toast.makeText(this, responseText, Toast.LENGTH_LONG).show()
+                val response = net.createGroup(groupName, groupPassword)
+                val responseText = response.body!!.string()
+
+                if (response.code == 200) {
+                    val currentGroups = sharedPreferences.getStringSet("groups", mutableSetOf())
+                    currentGroups!!.add(responseText)
+                    sharedPreferences.edit().putStringSet("groups", currentGroups).apply()
+                    sharedPreferences.edit().putString("currentGroup", responseText).apply()
+                    val intent = Intent(this, MainActivity::class.java)
+                    startActivity(intent)
+                    finish()
+                } else {
+                    Toast.makeText(this, responseText, Toast.LENGTH_LONG).show()
+                }
             }
         }
 
@@ -56,25 +60,36 @@ class GroupActivity : AppCompatActivity() {
             val groupName = binding.groupNameTextEdit.text.toString()
             val groupPassword = binding.groupPasswordTextEdit.text.toString()
 
-            val n = Net()
+            val net = Net()
-            n.language = sharedPreferences.getString("language", "en-US")!!
+            net.language = sharedPreferences.getString("language", "en-US")!!
-            n.server = sharedPreferences.getString("server", "")!!
+            net.server = sharedPreferences.getString("server", "")!!
-            n.token = sharedPreferences.getString("token", "")!!
+            net.token = sharedPreferences.getString("token", "")!!
 
-            val groupId = n.getGroupId(groupName).toInt()
+            if (!net.serverIsAvailable(this)) {
-            val response = n.joinGroup(groupId, groupPassword)
+                noInternetConnectionAvailableNotification(this)
-            val responseText = response.body!!.string()
-
-            if (response.code == 200) {
-                val currentGroups = sharedPreferences.getStringSet("groups", mutableSetOf())
-                currentGroups!!.add(groupId.toString())
-                sharedPreferences.edit().putStringSet("groups", currentGroups).apply()
-                sharedPreferences.edit().putString("currentGroup", groupId.toString()).apply()
-                val intent = Intent(this, MainActivity::class.java)
-                startActivity(intent)
-                finish()
             } else {
-                Toast.makeText(this, responseText, Toast.LENGTH_LONG).show()
+                val requestGroupIdResponse = net.getGroupId(groupName)
+                var groupId: Int
+                try {
+                   groupId = requestGroupIdResponse.toInt()
+                } catch (e: Exception) {
+                    Toast.makeText(this, requestGroupIdResponse, Toast.LENGTH_SHORT).show()
+                    return@setOnClickListener
+                }
+                val response = net.joinGroup(groupId, groupPassword)
+                val responseText = response.body!!.string()
+
+                if (response.code == 200) {
+                    val currentGroups = sharedPreferences.getStringSet("groups", mutableSetOf())
+                    currentGroups!!.add(groupId.toString())
+                    sharedPreferences.edit().putStringSet("groups", currentGroups).apply()
+                    sharedPreferences.edit().putString("currentGroup", groupId.toString()).apply()
+                    val intent = Intent(this, MainActivity::class.java)
+                    startActivity(intent)
+                    finish()
+                } else {
+                    Toast.makeText(this, responseText, Toast.LENGTH_LONG).show()
+                }
             }
         }
     }

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/LoginActivity.kt

@@ -10,6 +10,7 @@ import androidx.security.crypto.MasterKeys
 import org.foxarmy.barcodescannerforemployees.Net
 import org.foxarmy.barcodescannerforemployees.R
 import org.foxarmy.barcodescannerforemployees.databinding.ActivityLoginBinding
+import org.foxarmy.barcodescannerforemployees.noInternetConnectionAvailableNotification
 import org.foxarmy.barcodescannerforemployees.parseArray
 import org.json.JSONObject
 
@@ -40,31 +41,35 @@ class LoginActivity : AppCompatActivity() {
             val language = resources.getStringArray(R.array.languages)[binding.languageSpinner.selectedItemPosition]
             sharedPreferences.edit().putString("language", language).apply()
 
-            val n = Net()
+            val net = Net()
-            n.language = sharedPreferences.getString("language", "en-US")!!
+            net.language = sharedPreferences.getString("language", "en-US")!!
-            n.server = server
+            net.server = server
 
-            val response = n.login(username, password)
+            if (!net.serverIsAvailable(this)) {
-            val responseText = response.body!!.string()
+                noInternetConnectionAvailableNotification(this)
-            if (response.code != 200) {
-                Toast.makeText(this, responseText, Toast.LENGTH_SHORT).show()
             } else {
-                val json = JSONObject(responseText)
+                val response = net.login(username, password)
-                sharedPreferences.edit().putString("token", json["token"].toString()).apply()
+                val responseText = response.body!!.string()
-                n.token = json["token"].toString()
+                if (response.code != 200) {
-                sharedPreferences.edit().putInt("userId", json["id"].toString().toInt()).apply()
+                    Toast.makeText(this, responseText, Toast.LENGTH_SHORT).show()
-                sharedPreferences.edit().putString("server", server).apply()
+                } else {
+                    val json = JSONObject(responseText)
+                    sharedPreferences.edit().putString("token", json["token"].toString()).apply()
+                    net.token = json["token"].toString()
+                    sharedPreferences.edit().putInt("userId", json["id"].toString().toInt()).apply()
+                    sharedPreferences.edit().putString("server", server).apply()
 
 
-                val r = n.getMyGroups().body!!.string()
+                    val r = net.getMyGroups().body!!.string()
-                val myGroups = parseArray(r).map { a -> a.toString()}
+                    val myGroups = parseArray(r).map { a -> a.toString()}
 
-                sharedPreferences.edit().putStringSet("groups", myGroups.toSet()).apply()
+                    sharedPreferences.edit().putStringSet("groups", myGroups.toSet()).apply()
-                sharedPreferences.edit().putString("currentGroup", myGroups[0]).apply()
+                    sharedPreferences.edit().putString("currentGroup", myGroups[0]).apply()
 
-                val intent = Intent(this, MainActivity::class.java)
+                    val intent = Intent(this, MainActivity::class.java)
-                startActivity(intent)
+                    startActivity(intent)
-                finish()
+                    finish()
+                }
             }
         }
 
@@ -76,24 +81,38 @@ class LoginActivity : AppCompatActivity() {
             sharedPreferences.edit().putString("language", language).apply()
             sharedPreferences.edit().putString("server", server).apply()
 
-            val n = Net()
+            val net = Net()
-            n.language = language
+            net.language = language
-            n.server = server
+            net.server = server
-            val response = n.registerAccount(username, password);
-            val responseText = response.body!!.string()
-            if (response.code != 200) {
-                Toast.makeText(this, responseText, Toast.LENGTH_SHORT).show();
-            } else {
-                sharedPreferences.edit().putInt("userId", responseText.toInt()).apply()
-                val token = JSONObject(n.login(username, password).body!!.string())["token"].toString()
-                sharedPreferences.edit().putString("token", token).apply()
 
-                sharedPreferences.edit().putString("server", server).apply()
+            if (!net.serverIsAvailable(this)) {
-                val intent = Intent(this, GroupActivity::class.java)
+                noInternetConnectionAvailableNotification(this)
-                startActivity(intent)
+            } else {
-                finish()
+                val response = net.registerAccount(username, password);
+                val responseText = response.body!!.string()
+                if (response.code != 200) {
+                    Toast.makeText(this, responseText, Toast.LENGTH_SHORT).show();
+                } else {
+                    sharedPreferences.edit().putInt("userId", responseText.toInt()).apply()
+                    val token = JSONObject(net.login(username, password).body!!.string())["token"].toString()
+                    sharedPreferences.edit().putString("token", token).apply()
+
+                    sharedPreferences.edit().putString("server", server).apply()
+                    val intent = Intent(this, GroupActivity::class.java)
+                    startActivity(intent)
+                    finish()
+                }
             }
         }
+
+        binding.offlineButton.setOnClickListener {
+            sharedPreferences.edit().putString("currentGroup", "offline").apply()
+            sharedPreferences.edit().putStringSet("groups", setOf("offline")).apply()
+
+            val intent = Intent(this, MainActivity::class.java)
+            startActivity(intent)
+            finish()
+        }
     }
 
     private fun fillUpLanguagesSpinner() {

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/MainActivity.kt

@@ -3,9 +3,12 @@ package org.foxarmy.barcodescannerforemployees.activities
 import android.app.Activity
 import android.content.DialogInterface
 import android.content.Intent
+import android.content.SharedPreferences
 import android.os.Bundle
+import android.util.Log
 import android.view.Menu
 import android.view.MenuItem
+import android.widget.Toast
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.appcompat.app.ActionBarDrawerToggle
 import androidx.appcompat.app.AlertDialog
@@ -16,10 +19,7 @@ import androidx.security.crypto.EncryptedSharedPreferences
 import androidx.security.crypto.MasterKeys
 import androidx.viewpager.widget.ViewPager
 import com.google.android.material.navigation.NavigationView
-import org.foxarmy.barcodescannerforemployees.Net
+import org.foxarmy.barcodescannerforemployees.*
-import org.foxarmy.barcodescannerforemployees.R
-import org.foxarmy.barcodescannerforemployees.ViewPagerAdapter
-import org.foxarmy.barcodescannerforemployees.convertToUnixEpochTimestamp
 import org.foxarmy.barcodescannerforemployees.database.AbstractProductDAO
 import org.foxarmy.barcodescannerforemployees.database.CategoryDAO
 import org.foxarmy.barcodescannerforemployees.database.DBStorageController
@@ -39,9 +39,12 @@ import java.io.File
 class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelectedListener {
 
     private lateinit var binding: ActivityMainBinding
-    lateinit var adapter: ViewPagerAdapter
+    private lateinit var adapter: ViewPagerAdapter
-    var drawerLayout: DrawerLayout? = null
+    private var drawerLayout: DrawerLayout? = null
-    var actionBarDrawerToggle: ActionBarDrawerToggle? = null
+    private var actionBarDrawerToggle: ActionBarDrawerToggle? = null
+    private lateinit var ws: WebSocketClient
+
+    private lateinit var sharedPreferences: SharedPreferences
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -49,6 +52,14 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
         binding = ActivityMainBinding.inflate(layoutInflater)
         setContentView(binding.root)
 
+        sharedPreferences = EncryptedSharedPreferences.create(
+            "sensitive",
+            MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC),
+            applicationContext,
+            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+        )
+
         setSupportActionBar(binding.toolbar)
         setupViewPager(binding.tabViewpager)
         binding.tabTablayout.setupWithViewPager(binding.tabViewpager)
@@ -60,9 +71,16 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
         actionBarDrawerToggle!!.syncState()
         binding.navView.setNavigationItemSelectedListener(this)
 
-        // to make the Navigation drawer icon always appear on the action bar
         supportActionBar!!.setDisplayHomeAsUpEnabled(true)
 
+        val sharedPreferences = EncryptedSharedPreferences.create(
+            "sensitive",
+            MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC),
+            applicationContext,
+            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+        )
+
         binding.expiryCalendarFab.setOnClickListener { _ ->
             val expiryCalendarIntent = Intent(this, ExpiryCalendarActivity::class.java)
             val extras = Bundle()
@@ -78,8 +96,6 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
                 "StorageFragment" -> {
                     val addAbstractProductIntent = Intent(this, AddAbstractProductActivity::class.java)
                     val extras = Bundle()
-                    // I reuse the same stuff for editing and adding new product.
-                    // if abstractProduct == null, it means that we need to create new object
                     extras.putParcelable("abstractProduct", null)
                     extras.putString("action", "new")
                     addAbstractProductIntent.putExtras(extras)
@@ -104,19 +120,20 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
                 }
             }
         }
-        synchronize()
+        val net = Net()
+        net.server = sharedPreferences.getString("server", "")!!
+        val currentGroup = sharedPreferences.getString("currentGroup", "offline")!!
+        if ( currentGroup != "offline" && !net.serverIsAvailable(this)) {
+            noInternetConnectionAvailableNotification(this)
+        } else if (currentGroup != "offline" && net.serverIsAvailable(this)) {
+            synchronize()
+            ws = WebSocketClient(this, sharedPreferences.getString("server", "")!!)
+            val token = sharedPreferences.getString("token", "")!!
+            ws.connect(token, currentGroup)
+        }
     }
 
     private fun synchronize() {
-
-        val sharedPreferences = EncryptedSharedPreferences.create(
-            "sensitive",
-            MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC),
-            applicationContext,
-            EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
-            EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
-        )
-
         if (sharedPreferences.getString("currentGroup", "offline")!! == "offline") return
 
         val net = Net()
@@ -194,15 +211,7 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
 
             if (categoryInRemoteDB != null && categoryInLocalDB != null) {
                 if (categoryInRemoteDB["hash"] != categoryInLocalDB.calculateHash()) {
-
+                    val updatedData = Category.createFromJSON(categoryInRemoteDB)
-                    var updatedData: Category
-
-                    with(categoryInRemoteDB) {
-                        updatedData = Category(
-                            this["local_id"].toString().toInt(),
-                            this["name"].toString()
-                        )
-                    }
 
                     categoryDAO.updateCategory(updatedData)
                 }
@@ -241,35 +250,14 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
             }
 
             if (productInLocalDB == null && remoteProduct != null) {
-                var newProduct: Product
+                val newProduct = Product.createFromJSON(remoteProduct)
-
-                with(remoteProduct) {
-                    newProduct = Product(
-                        this["local_id"].toString().toInt(),
-                        this["abstract_product_id"].toString().toInt(),
-                        this["amount"].toString().toInt(),
-                        convertToUnixEpochTimestamp(this["date_of_production"].toString()),
-                        convertToUnixEpochTimestamp(this["expiry_date"].toString())
-                    )
-                }
 
                 productDAO.insertNewProduct(newProduct)
             }
 
             if (productInRemoteDB != null && productInLocalDB != null) {
                 if (productInRemoteDB["hash"] != productInLocalDB.calculateHash()) {
-
+                    val updatedData = Product.createFromJSON(productInRemoteDB)
-                    var updatedData: Product
-
-                    with(productInRemoteDB) {
-                        updatedData = Product(
-                            this["local_id"].toString().toInt(),
-                            this["abstract_product_id"].toString().toInt(),
-                            this["amount"].toString().toInt(),
-                            convertToUnixEpochTimestamp(this["date_of_production"].toString()),
-                            convertToUnixEpochTimestamp(this["expiry_date"].toString())
-                        )
-                    }
 
                     productDAO.updateProduct(updatedData)
                 }
@@ -320,19 +308,7 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
                 val url = "https://${net.server}/api/abstractproduct/getImage/${currentGroup}/${localId}"
                 net.downloadImage(url, pictureFile)
 
-                var newAbstractProduct: AbstractProduct
+                val newAbstractProduct = AbstractProduct.createFromJSON(remoteAbstractProduct)
-
-                with(remoteAbstractProduct) {
-                    newAbstractProduct = AbstractProduct(
-                        this["local_id"].toString().toInt(),
-                        this["barcode"].toString(),
-                        this["name"].toString(),
-                        this["net_weight"].toString().toDouble(),
-                        this["image_filename"].toString(),
-                        this["category"].toString().toInt(),
-                        this["unit"].toString().toInt()
-                    )
-                }
 
                 abstractProductDAO.addAbstractProduct(newAbstractProduct)
 
@@ -347,20 +323,7 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
                     val url = "https://${net.server}/api/abstractproduct/getImage/${currentGroup}/${localId}"
                     net.downloadImage(url, pictureFile)
 
-                    var updatedData: AbstractProduct
+                    val updatedData = AbstractProduct.createFromJSON(abstractProductInRemoteDB)
-
-                    with(abstractProductInRemoteDB) {
-                        updatedData = AbstractProduct(
-                            this["local_id"].toString().toInt(),
-                            this["barcode"].toString(),
-                            this["name"].toString(),
-                            this["net_weight"].toString().toDouble(),
-                            this["image_filename"].toString(),
-                            this["category"].toString().toInt(),
-                            this["unit"].toString().toInt()
-                        )
-                    }
-
 
                     abstractProductDAO.updateAbstractProduct(updatedData)
                 }
@@ -384,22 +347,43 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
         return true
     }
 
+    private fun isOffline(): Boolean {
+        return sharedPreferences.getString("currentGroup", "") == "offline"
+    }
+
     override fun onNavigationItemSelected(item: MenuItem): Boolean {
         lateinit var intent: Intent
         when (item.itemId) {
             R.id.nav_account -> {
+                if (isOffline()) {
+                    Toast.makeText(this, getString(R.string.online_only_feature), Toast.LENGTH_SHORT).show()
+                    return false
+                }
                 intent = Intent(this, AccountSettingsActivity::class.java)
                 settingsActivityLauncher.launch(intent)
                 return true
             }
 
             R.id.nav_groups -> {
+                if (isOffline()) {
+                    Toast.makeText(this, getString(R.string.online_only_feature), Toast.LENGTH_SHORT).show()
+                    return false
+                }
                 intent = Intent(this, MyGroupsActivity::class.java)
             }
 
             R.id.nav_settings -> {
                 intent = Intent(this, SettingsActivity::class.java)
             }
+
+            R.id.nav_logout -> {
+                sharedPreferences.edit().putString("currentGroup", "").apply()
+                sharedPreferences.edit().putStringSet("groups", emptySet()).apply()
+                sharedPreferences.edit().putString("token", "").apply()
+                sharedPreferences.edit().putString("server", "").apply()
+
+                intent = Intent(this, LoginActivity::class.java)
+            }
         }
         startActivity(intent)
 
@@ -416,13 +400,19 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
     }
 
     fun updateAll() {
-        val storageFragment: StorageFragment = adapter.getItem(0) as StorageFragment
+        runOnUiThread {
-        val shelfFragment: ShelfFragment = adapter.getItem(1) as ShelfFragment
+            try {
-        val categoriesFragment: CategoriesFragment = adapter.getItem(2) as CategoriesFragment
+                val storageFragment: StorageFragment = adapter.getItem(0) as StorageFragment
+                val shelfFragment: ShelfFragment = adapter.getItem(1) as ShelfFragment
+                val categoriesFragment: CategoriesFragment = adapter.getItem(2) as CategoriesFragment
 
-        storageFragment.updateContent()
+                storageFragment.updateContent()
-        shelfFragment.updateContent()
+                shelfFragment.updateContent()
-        categoriesFragment.updateContent()
+                categoriesFragment.updateContent()
+            } catch (e:Exception) {
+                Log.e("BSFE/MainActivity", e.message!!)
+            }
+        }
     }
 
     override fun onOptionsItemSelected(item: MenuItem): Boolean {

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/NavigatorActivity.kt

@@ -24,19 +24,22 @@ class NavigatorActivity : Activity() {
 
         var intent = Intent(this, MainActivity::class.java)
 
-        if (!isInGroup()) {
+        if (!isInGroup() && !isOffline()) {
             intent = Intent(this, GroupActivity::class.java)
         }
 
-        if (!isAuthenticated()) {
+        if (!isAuthenticated() && !isOffline()) {
             intent = Intent(this, LoginActivity::class.java);
         }
 
-
         startActivity(intent);
         finish();
     }
 
+    private fun isOffline(): Boolean {
+        return sharedPreferences.getString("currentGroup", "")!! == "offline"
+    }
+
     private fun isAuthenticated(): Boolean {
         return sharedPreferences.getString("token", "") != ""
     }

app/src/main/java/org/foxarmy/barcodescannerforemployees/activities/SettingsActivity.kt

@@ -37,17 +37,23 @@ class SettingsActivity : AppCompatActivity() {
         net.language = sharedPreferences.getString("language", "")!!
         net.server = sharedPreferences.getString("server", "")!!
 
-        groupsNames = mutableListOf()
-
-        for (myGroup in myGroups) {
-            groupsNames.add(net.getGroupName(myGroup.toInt()))
-        }
-
         binding = ActivitySettingsBinding.inflate(layoutInflater)
         setContentView(binding.root)
 
         setUpImageCompressionSeekBar()
-        fillUpCurrentGroupSpinner()
+
+
+        if (isOffline()) {
+            binding.currentGroupSetting.visibility = View.GONE
+        } else {
+            groupsNames = mutableListOf()
+
+            for (myGroup in myGroups) {
+                groupsNames.add(net.getGroupName(myGroup.toInt()))
+            }
+
+            fillUpCurrentGroupSpinner()
+        }
 
         binding.saveButton.setOnClickListener {
             sharedPreferences.edit().putString("currentGroup", net.getGroupId(binding.currentGroupSpinner.selectedItem.toString())).apply()
@@ -62,14 +68,16 @@ class SettingsActivity : AppCompatActivity() {
         }
     }
 
+    private fun isOffline(): Boolean {
+        return sharedPreferences.getString("currentGroup", "offline") == "offline"
+    }
+
     private fun setUpImageCompressionSeekBar() {
         val compressionFactor = sharedPreferences.getInt("imageCompression", 1)
         binding.imageCompressionFactorSeekBar.progress = compressionFactor - 1
     }
 
     private fun fillUpCurrentGroupSpinner() {
-
-
         if (currentGroup == "offline") {
             binding.currentGroupSetting.visibility = View.GONE
         }

app/src/main/java/org/foxarmy/barcodescannerforemployees/database/AbstractProductDAO.kt

@@ -163,7 +163,7 @@ class AbstractProductDAO(private val dbHelper: DBStorageController) {
 
         with(cursor) {
             while (moveToNext()) {
-                val id = getInt(getColumnIndexOrThrow(android.provider.BaseColumns._ID))
+                val id = getInt(getColumnIndexOrThrow(BaseColumns._ID))
                 val productName =
                     getString(getColumnIndexOrThrow(AbstractProductContract.AbstractProductEntry.PRODUCT_NAME))
                 val imageFilename =

app/src/main/java/org/foxarmy/barcodescannerforemployees/dataclasses/AbstractProduct.kt

@@ -3,6 +3,7 @@ package org.foxarmy.barcodescannerforemployees.dataclasses
 import android.os.Parcel
 import android.os.Parcelable
 import org.foxarmy.barcodescannerforemployees.md5
+import org.json.JSONObject
 
 class AbstractProduct() : Parcelable {
     var id: Int = 0
@@ -59,5 +60,17 @@ class AbstractProduct() : Parcelable {
         override fun newArray(size: Int): Array<AbstractProduct?> {
             return arrayOfNulls(size)
         }
+
+        fun createFromJSON(json: JSONObject): AbstractProduct {
+            return AbstractProduct(
+                json["local_id"].toString().toInt(),
+                json["barcode"].toString(),
+                json["name"].toString(),
+                json["net_weight"].toString().toDouble(),
+                json["image_filename"].toString(),
+                json["category"].toString().toInt(),
+                json["unit"].toString().toInt()
+            )
+        }
     }
 }

app/src/main/java/org/foxarmy/barcodescannerforemployees/dataclasses/Category.kt

@@ -3,6 +3,7 @@ package org.foxarmy.barcodescannerforemployees.dataclasses
 import android.os.Parcel
 import android.os.Parcelable
 import org.foxarmy.barcodescannerforemployees.md5
+import org.json.JSONObject
 
 class Category() : Parcelable {
     var id = 0
@@ -40,5 +41,12 @@ class Category() : Parcelable {
         override fun newArray(size: Int): Array<Category?> {
             return arrayOfNulls(size)
         }
+
+        fun createFromJSON(json: JSONObject): Category {
+            return Category(
+                json["local_id"].toString().toInt(),
+                json["name"].toString()
+            )
+        }
     }
 }

app/src/main/java/org/foxarmy/barcodescannerforemployees/dataclasses/Product.kt

@@ -5,7 +5,9 @@ import android.os.Parcel
 import android.os.Parcelable
 import androidx.annotation.RequiresApi
 import org.foxarmy.barcodescannerforemployees.calculateProductFreshness
+import org.foxarmy.barcodescannerforemployees.convertToUnixEpochTimestamp
 import org.foxarmy.barcodescannerforemployees.md5
+import org.json.JSONObject
 
 class Product() : Parcelable {
     var id = 0
@@ -59,5 +61,16 @@ class Product() : Parcelable {
         override fun newArray(size: Int): Array<Product?> {
             return arrayOfNulls(size)
         }
+
+        @RequiresApi(Build.VERSION_CODES.O)
+        fun createFromJSON(json: JSONObject): Product {
+            return Product(
+                json["local_id"].toString().toInt(),
+                json["abstract_product_id"].toString().toInt(),
+                json["amount"].toString().toInt(),
+                convertToUnixEpochTimestamp(json["date_of_production"].toString()),
+                convertToUnixEpochTimestamp(json["expiry_date"].toString())
+            )
+        }
     }
 }

app/src/main/java/org/foxarmy/barcodescannerforemployees/fragments/StorageFragment.kt

@@ -37,6 +37,8 @@ class StorageFragment : Fragment() {
         inflater: LayoutInflater, container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View {
+        binding = FragmentStorageBinding.inflate(inflater)
+
         sharedPreferences = EncryptedSharedPreferences.create(
             "sensitive",
             MasterKeys.getOrCreate(MasterKeys.AES256_GCM_SPEC),
@@ -47,8 +49,6 @@ class StorageFragment : Fragment() {
 
         prepareDatabaseConnection()
 
-        binding = FragmentStorageBinding.inflate(inflater)
-
         fillUpSortBySpinner()
 
         binding.spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {

app/src/main/res/layout/fragment_add_abstract_product.xml

@@ -62,7 +62,7 @@
                 android:ems="10"
                 android:id="@+id/barcodeTextEdit" app:layout_constraintTop_toBottomOf="@+id/imageView"
                 app:layout_constraintStart_toStartOf="parent"
-                android:layout_marginTop="8dp" android:hint="Barcode" android:textColorHint="#737373"
+                android:layout_marginTop="8dp" android:hint="@string/barcode" android:textColorHint="#737373"
                 android:layout_marginStart="5dp"/>
         <CheckBox
                 android:text="@string/no_barcode"

app/src/main/res/layout/fragment_shelf.xml

@@ -2,7 +2,7 @@
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent"
              android:layout_height="match_parent"
-             android:background="#141218">
+>
 
     <androidx.constraintlayout.widget.ConstraintLayout
             android:layout_width="match_parent"

app/src/main/res/menu/drawer_menu.xml

@@ -12,4 +12,5 @@
     <item
             android:id="@+id/nav_settings"
             android:title="@string/settings"/>
+    <item android:title="@string/logout" android:id="@+id/nav_logout"/>
 </menu>

app/src/main/res/values-ru/strings.xml

@@ -114,6 +114,10 @@
     <string name="image_compress_factor">Степень сжатия изображения</string>
     <string name="current_group">Текущая группа</string>
     <string name="cancel">Отмена</string>
+    <string name="no_internet_connection">Не могу установить соединение с сервером. Возможно, вы отключены от сети?</string>
+    <string name="ok">Ок</string>
+    <string name="logout">Выйти</string>
+    <string name="online_only_feature">Эта возможность доступна только с онлайн аккаунтом</string>
     <string-array name="languages">
         <item>en-US</item>
         <item>ru-RU</item>

app/src/main/res/values/strings.xml

@@ -112,6 +112,10 @@
     <string name="image_compress_factor">Image compression factor</string>
     <string name="current_group">Current group</string>
     <string name="cancel">Cancel</string>
+    <string name="no_internet_connection">Cannot reach the server. Maybe, you lost internet connection?</string>
+    <string name="ok">OK</string>
+    <string name="logout">Log out</string>
+    <string name="online_only_feature">This feature is online only</string>
     <string-array name="languages">
         <item>en-US</item>
         <item>ru-RU</item>