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
@@ -34,49 +36,53 @@ class DataFetcher {
     }
 
     @Throws(IOException::class)
-    fun getCircularsFromServer(): List<Circular> {
-        val json = gson.fromJson(retrieveDataFromServer(), Response::class.java)
+    suspend fun getCircularsFromServer(): List<Circular> {
+        return withContext(Dispatchers.Default) {
+            val json = gson.fromJson(retrieveDataFromServer(), Response::class.java)
 
-        val document = Jsoup.parseBodyFragment(json.content!!.rendered)
-        val htmlList = document.getElementsByTag("ul")[0].getElementsByTag("a")
+            val document = Jsoup.parseBodyFragment(json.content!!.rendered)
+            val htmlList = document.getElementsByTag("ul")[0].getElementsByTag("a")
 
-        val list = ArrayList<Circular>()
+            val list = ArrayList<Circular>()
 
-        htmlList.forEach { element ->
-            if (element.parents().size == 6) {
-                list.last().attachmentsNames.add(element.text())
-                list.last().attachmentsUrls.add(element.attr("href"))
-            } else if (element.parents().size == 4) {
-                list.add(Circular.generateFromString(element.text(), element.attr("href")))
+            htmlList.forEach { element ->
+                if (element.parents().size == 6) {
+                    list.last().attachmentsNames.add(element.text())
+                    list.last().attachmentsUrls.add(element.attr("href"))
+                } else if (element.parents().size == 4) {
+                    list.add(Circular.generateFromString(element.text(), element.attr("href")))
+                }
             }
-        }
 
-        return list
+            list
+        }
     }
 
     @Throws(IOException::class)
-    fun retrieveDataFromServer(): String? {
+    private suspend fun retrieveDataFromServer(): String? {
         var connection: HttpsURLConnection? = null
-        return try {
-            connection = (URL(ENDPOINT_URL).openConnection() as? HttpsURLConnection)
-            connection?.run {
-                // Set GET HTTP method
-                requestMethod = "GET"
 
-                setRequestProperty("Accept-Encoding", "none")
+        return withContext(Dispatchers.IO) {
+            try {
+                connection = (URL(ENDPOINT_URL).openConnection() as? HttpsURLConnection)
+                connection?.run {
+                    // Set GET HTTP method
+                    requestMethod = "GET"
 
-                connect()
-                if (responseCode != HttpsURLConnection.HTTP_OK) {
-                    throw IOException("HTTP error code: $responseCode")
+                    setRequestProperty("Accept-Encoding", "none")
+
+                    connect()
+                    if (responseCode != HttpsURLConnection.HTTP_OK) {
+                        throw IOException("HTTP error code: $responseCode")
+                    }
+
+                    inputStream?.reader()?.readText()
                 }
-
-                inputStream?.reader()?.readText()
+            } finally {
+                // Close Stream and disconnect HTTPS connection.
+                connection?.inputStream?.close()
+                connection?.disconnect()
             }
-        } finally {
-            // Close Stream and disconnect HTTPS connection.
-            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.LiveData
-import androidx.lifecycle.MutableLiveData
-import androidx.lifecycle.Transformations
+import androidx.lifecycle.*
+import kotlinx.coroutines.launch
 import net.underdesk.circolapp.data.AppDatabase
 import net.underdesk.circolapp.data.Circular
 import net.underdesk.circolapp.server.DataFetcher
@@ -48,25 +46,23 @@ class CircularLetterViewModel(application: Application) : AndroidViewModel(appli
 
     fun updateCirculars() {
         if (isNotUpdating) {
-            object : Thread() {
-                override fun run() {
-                    isNotUpdating = false
-                    val fetcher = DataFetcher()
+            viewModelScope.launch {
+                isNotUpdating = false
+                val fetcher = DataFetcher()
 
-                    try {
-                        val newCirculars = fetcher.getCircularsFromServer()
-                        if (newCirculars.size != circulars.value?.size ?: true) {
-                            AppDatabase.getInstance(getApplication()).circularDao()
-                                .insertAll(newCirculars)
-                        }
-                    } catch (exception: IOException) {
-                        showMessage.postValue(true)
-                    } finally {
-                        isNotUpdating = true
-                        circularsUpdated.postValue(true)
+                try {
+                    val newCirculars = fetcher.getCircularsFromServer()
+                    if (newCirculars.size != circulars.value?.size ?: true) {
+                        AppDatabase.getInstance(getApplication()).circularDao()
+                            .insertAll(newCirculars)
                     }
+                } catch (exception: IOException) {
+                    showMessage.postValue(true)
+                } finally {
+                    isNotUpdating = true
+                    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"
@@ -84,52 +87,59 @@ 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()
-        val newCirculars = try {
-            fetcher.getCircularsFromServer()
-        } catch (exception: IOException) {
-            return Result.retry()
-        }
-
-        if (newCirculars.size != oldCirculars.size) {
-            createNotificationChannel()
-
-            val summaryStyle = NotificationCompat.InboxStyle()
-                .setBigContentTitle(applicationContext.getString(R.string.notification_summary_title))
-                .setSummaryText(applicationContext.getString(R.string.notification_summary))
-
-            val circularCount = newCirculars.size - oldCirculars.size
-
-            for (i in 0 until circularCount) {
-                createNotification(newCirculars[i])
-                summaryStyle.addLine(newCirculars[i].name)
+        withContext(Dispatchers.IO) {
+            val oldCirculars =
+                AppDatabase.getInstance(applicationContext).circularDao().getCirculars()
+            val newCirculars = try {
+                fetcher.getCircularsFromServer()
+            } catch (exception: IOException) {
+                return@withContext Result.retry()
             }
 
-            val summaryNotification = NotificationCompat.Builder(applicationContext, CHANNEL_ID)
-                .setContentTitle(applicationContext.getString(R.string.notification_summary_title))
-                .setContentText(
-                    applicationContext.resources.getQuantityString(
-                        R.plurals.notification_summary_text,
-                        circularCount,
-                        circularCount
-                    )
-                )
-                .setSmallIcon(R.drawable.ic_notification)
-                .setStyle(summaryStyle)
-                .setGroup(CHANNEL_ID)
-                .setGroupSummary(true)
-                .build()
+            if (newCirculars.size != oldCirculars.size) {
+                withContext(Dispatchers.Main) {
+                    createNotificationChannel()
 
-            with(NotificationManagerCompat.from(applicationContext)) {
-                notify(-1, summaryNotification)
+                    val summaryStyle = NotificationCompat.InboxStyle()
+                        .setBigContentTitle(applicationContext.getString(R.string.notification_summary_title))
+                        .setSummaryText(applicationContext.getString(R.string.notification_summary))
+
+                    val circularCount = newCirculars.size - oldCirculars.size
+
+                    for (i in 0 until circularCount) {
+                        createNotification(newCirculars[i])
+                        summaryStyle.addLine(newCirculars[i].name)
+                    }
+
+                    val summaryNotification =
+                        NotificationCompat.Builder(applicationContext, CHANNEL_ID)
+                            .setContentTitle(applicationContext.getString(R.string.notification_summary_title))
+                            .setContentText(
+                                applicationContext.resources.getQuantityString(
+                                    R.plurals.notification_summary_text,
+                                    circularCount,
+                                    circularCount
+                                )
+                            )
+                            .setSmallIcon(R.drawable.ic_notification)
+                            .setStyle(summaryStyle)
+                            .setGroup(CHANNEL_ID)
+                            .setGroupSummary(true)
+                            .build()
+
+                    with(NotificationManagerCompat.from(applicationContext)) {
+                        notify(-1, summaryNotification)
+                    }
+                }
+
+                AppDatabase.getInstance(applicationContext).circularDao()
+                    .insertAll(newCirculars)
             }
-
-            AppDatabase.getInstance(applicationContext).circularDao().insertAll(newCirculars)
+            Result.success()
         }
-        return Result.success()
     }
 
     private fun createNotification(circular: Circular) {