Use coroutines instead of threads

app/src/main/java/net/underdesk/circolapp/server/DataFetcher.kt

@@ -19,6 +19,8 @@
 package net.underdesk.circolapp.server
 
 import com.google.gson.Gson
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
 import net.underdesk.circolapp.data.Circular
 import net.underdesk.circolapp.server.pojo.Response
 import org.jsoup.Jsoup
@@ -34,7 +36,8 @@ class DataFetcher {
     }
 
     @Throws(IOException::class)
-    fun getCircularsFromServer(): List<Circular> {
+    suspend fun getCircularsFromServer(): List<Circular> {
+        return withContext(Dispatchers.Default) {
             val json = gson.fromJson(retrieveDataFromServer(), Response::class.java)
 
             val document = Jsoup.parseBodyFragment(json.content!!.rendered)
@@ -51,13 +54,16 @@ class DataFetcher {
                 }
             }
 
-        return list
+            list
+        }
     }
 
     @Throws(IOException::class)
-    fun retrieveDataFromServer(): String? {
+    private suspend fun retrieveDataFromServer(): String? {
         var connection: HttpsURLConnection? = null
-        return try {
+
+        return withContext(Dispatchers.IO) {
+            try {
                 connection = (URL(ENDPOINT_URL).openConnection() as? HttpsURLConnection)
                 connection?.run {
                     // Set GET HTTP method
@@ -77,6 +83,6 @@ class DataFetcher {
                 connection?.inputStream?.close()
                 connection?.disconnect()
             }
-
+        }
     }
 }

app/src/main/java/net/underdesk/circolapp/viewmodels/CircularLetterViewModel.kt

@@ -19,10 +19,8 @@
 package net.underdesk.circolapp.viewmodels
 
 import android.app.Application
-import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.*
-import androidx.lifecycle.LiveData
+import kotlinx.coroutines.launch
-import androidx.lifecycle.MutableLiveData
-import androidx.lifecycle.Transformations
 import net.underdesk.circolapp.data.AppDatabase
 import net.underdesk.circolapp.data.Circular
 import net.underdesk.circolapp.server.DataFetcher
@@ -48,8 +46,7 @@ class CircularLetterViewModel(application: Application) : AndroidViewModel(appli
 
     fun updateCirculars() {
         if (isNotUpdating) {
-            object : Thread() {
+            viewModelScope.launch {
-                override fun run() {
                 isNotUpdating = false
                 val fetcher = DataFetcher()
 
@@ -66,7 +63,6 @@ class CircularLetterViewModel(application: Application) : AndroidViewModel(appli
                     circularsUpdated.postValue(true)
                 }
             }
-            }.start()
         }
     }
 }

app/src/main/java/net/underdesk/circolapp/works/PollWork.kt

@@ -30,6 +30,9 @@ import androidx.core.app.NotificationManagerCompat
 import androidx.core.app.TaskStackBuilder
 import androidx.preference.PreferenceManager
 import androidx.work.*
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.coroutineScope
+import kotlinx.coroutines.withContext
 import net.underdesk.circolapp.MainActivity
 import net.underdesk.circolapp.R
 import net.underdesk.circolapp.data.AppDatabase
@@ -40,7 +43,7 @@ import java.util.concurrent.TimeUnit
 
 
 class PollWork(appContext: Context, workerParams: WorkerParameters) :
-    Worker(appContext, workerParams) {
+    CoroutineWorker(appContext, workerParams) {
 
     companion object {
         const val CHANNEL_ID = "net.underdesk.circolapp.NEW_CIRCULAR"
@@ -84,17 +87,20 @@ class PollWork(appContext: Context, workerParams: WorkerParameters) :
         }
     }
 
-    override fun doWork(): Result {
+    override suspend fun doWork(): Result = coroutineScope {
         val fetcher = DataFetcher()
 
-        val oldCirculars = AppDatabase.getInstance(applicationContext).circularDao().getCirculars()
+        withContext(Dispatchers.IO) {
+            val oldCirculars =
+                AppDatabase.getInstance(applicationContext).circularDao().getCirculars()
             val newCirculars = try {
                 fetcher.getCircularsFromServer()
             } catch (exception: IOException) {
-            return Result.retry()
+                return@withContext Result.retry()
             }
 
             if (newCirculars.size != oldCirculars.size) {
+                withContext(Dispatchers.Main) {
                     createNotificationChannel()
 
                     val summaryStyle = NotificationCompat.InboxStyle()
@@ -108,7 +114,8 @@ class PollWork(appContext: Context, workerParams: WorkerParameters) :
                         summaryStyle.addLine(newCirculars[i].name)
                     }
 
-            val summaryNotification = NotificationCompat.Builder(applicationContext, CHANNEL_ID)
+                    val summaryNotification =
+                        NotificationCompat.Builder(applicationContext, CHANNEL_ID)
                             .setContentTitle(applicationContext.getString(R.string.notification_summary_title))
                             .setContentText(
                                 applicationContext.resources.getQuantityString(
@@ -126,10 +133,13 @@ class PollWork(appContext: Context, workerParams: WorkerParameters) :
                     with(NotificationManagerCompat.from(applicationContext)) {
                         notify(-1, summaryNotification)
                     }
-
-            AppDatabase.getInstance(applicationContext).circularDao().insertAll(newCirculars)
                 }
-        return Result.success()
+
+                AppDatabase.getInstance(applicationContext).circularDao()
+                    .insertAll(newCirculars)
+            }
+            Result.success()
+        }
     }
 
     private fun createNotification(circular: Circular) {