android notif [nfc]: Use compat version for notification modules.

Compat version of modules allow us to write code for the latest
android version without worrying about backwards compatibility, all
that will be handled by the compat modules.

Specifically the changes are made for:
* Notification -> NotificationCompat
* NotificationManager -> NotificationCompatManager

Some associated code is also changed as required.

reference:
- https://developer.android.com/guide/topics/ui/notifiers/notifications#compatibility

android/app/src/main/java/com/zulipmobile/notifications/FCMPushNotifications.kt

@@ -2,20 +2,20 @@
 
 package com.zulipmobile.notifications
 
-import android.app.Notification
+import android.annotation.SuppressLint
 import android.app.NotificationChannel
-import android.app.NotificationManager
 import android.app.PendingIntent
 import android.content.Context
 import android.content.Intent
 import android.graphics.Color
-import android.media.AudioAttributes
 import android.net.Uri
 import android.os.Build
 import android.os.Bundle
 import android.provider.Settings
 import android.text.TextUtils
 import android.util.Log
+import androidx.core.app.NotificationManagerCompat
+import androidx.core.app.NotificationCompat
 import com.facebook.react.ReactApplication
 import me.leolin.shortcutbadger.ShortcutBadger
 
@@ -31,14 +31,19 @@ val ACTION_CLEAR = "ACTION_CLEAR"
 @JvmField
 val EXTRA_NOTIFICATION_DATA = "data"
 
-private fun getNotificationManager(context: Context): NotificationManager {
-    return context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
+private fun getNotificationManager(context: Context): NotificationManagerCompat {
+    return NotificationManagerCompat.from(context)
 }
 
 fun createNotificationChannel(context: Context) {
     if (Build.VERSION.SDK_INT >= 26) {
         val name = context.getString(R.string.notification_channel_name)
-        val channel = NotificationChannel(CHANNEL_ID, name, NotificationManager.IMPORTANCE_HIGH)
+
+        @SuppressLint("WrongConstant")
+        // Android Studio's linter demands NotificationManager.IMPORTANCE_* and rejects any other
+        // value, hence using "SupressLint".
+        val channel =
+            NotificationChannel(CHANNEL_ID, name, NotificationManagerCompat.IMPORTANCE_HIGH)
         getNotificationManager(context).createNotificationChannel(channel)
     }
 }
@@ -92,11 +97,8 @@ private fun getNotificationSoundUri(context: Context): Uri {
 }
 
 private fun getNotificationBuilder(
-    context: Context, conversations: ConversationMap, fcmMessage: MessageFcmMessage): Notification.Builder {
-    val builder = if (Build.VERSION.SDK_INT >= 26)
-        Notification.Builder(context, CHANNEL_ID)
-    else
-        Notification.Builder(context)
+    context: Context, conversations: ConversationMap, fcmMessage: MessageFcmMessage): NotificationCompat.Builder {
+    val builder = NotificationCompat.Builder(context, CHANNEL_ID)
 
     val uri = Uri.fromParts("zulip", "msgid:${fcmMessage.zulipMessageId}", "")
     val viewIntent = Intent(Intent.ACTION_VIEW, uri, context, NotificationIntentService::class.java)
@@ -133,13 +135,13 @@ private fun getNotificationBuilder(
         }
         fetchBitmap(sizedURL(context, fcmMessage.sender.avatarURL, 64f))
             ?.let { builder.setLargeIcon(it) }
-        builder.setStyle(Notification.BigTextStyle().bigText(fcmMessage.content))
+        builder.setStyle(NotificationCompat.BigTextStyle().bigText(fcmMessage.content))
     } else {
         val numConversations = context.resources.getQuantityString(
             R.plurals.numConversations, conversations.size, conversations.size)
         builder.setContentTitle("$totalMessagesCount messages in $numConversations")
         builder.setContentText("Messages from ${TextUtils.join(",", nameList)}")
-        val inboxStyle = Notification.InboxStyle(builder)
+        val inboxStyle = NotificationCompat.InboxStyle(builder)
         inboxStyle.setSummaryText(numConversations)
         buildNotificationContent(conversations, inboxStyle)
         builder.setStyle(inboxStyle)
@@ -159,18 +161,16 @@ private fun getNotificationBuilder(
     // TODO: choose a vibration pattern we like, and unset DEFAULT_VIBRATE.
     builder.setVibrate(vPattern)
 
-    builder.setDefaults(Notification.DEFAULT_VIBRATE or Notification.DEFAULT_LIGHTS)
+    builder.setDefaults(NotificationCompat.DEFAULT_VIBRATE or NotificationCompat.DEFAULT_LIGHTS)
 
     val dismissIntent = Intent(context, NotificationIntentService::class.java)
     dismissIntent.action = ACTION_CLEAR
     val piDismiss = PendingIntent.getService(context, 0, dismissIntent, 0)
-    val action = Notification.Action(android.R.drawable.ic_menu_close_clear_cancel, "Clear", piDismiss)
+    val action = NotificationCompat.Action(android.R.drawable.ic_menu_close_clear_cancel, "Clear", piDismiss)
     builder.addAction(action)
 
     val soundUri = getNotificationSoundUri(context)
-    val audioAttr = AudioAttributes.Builder()
-        .setUsage(AudioAttributes.USAGE_NOTIFICATION).build()
-    builder.setSound(soundUri, audioAttr)
+    builder.setSound(soundUri)
     return builder
 }
 

android/app/src/main/java/com/zulipmobile/notifications/NotificationHelper.kt

@@ -2,7 +2,6 @@
 
 package com.zulipmobile.notifications
 
-import android.app.Notification
 import android.content.Context
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
@@ -12,6 +11,7 @@ import android.text.TextUtils
 import android.text.style.StyleSpan
 import android.util.Log
 import android.util.TypedValue
+import androidx.core.app.NotificationCompat
 import java.io.IOException
 import java.io.InputStream
 import java.net.URL
@@ -64,7 +64,7 @@ fun sizedURL(context: Context, url: URL, dpSize: Float): URL {
     return URL(url, "?$query")
 }
 
-fun buildNotificationContent(conversations: ByConversationMap, inboxStyle: Notification.InboxStyle) {
+fun buildNotificationContent(conversations: ByConversationMap, inboxStyle: NotificationCompat.InboxStyle) {
     for (conversation in conversations.values) {
         // TODO ensure latest sender is shown last?  E.g. Gmail-style A, B, ..., A.
         val seenSenders = HashSet<String>()