NAVAND-1001: use immediate dispatcher to guarantee that language will change before voice instructions

Author: dzinad

CHANGELOG.md

@@ -25,6 +25,7 @@ Mapbox welcomes participation and contributions from everyone.
   ```
 - Added guarantees that route progress with `RouteProgress#currentState == OFF_ROUTE` arrives earlier than `NavigationRerouteController#reroute` is called. [#6764](https://github.com/mapbox/mapbox-navigation-android/pull/6764)
 - Fixed a rare `java.lang.NullPointerException: Attempt to read from field 'SpeechAnnouncement PlayCallback.announcement' on a null object reference` crash in `PlayCallback.getAnnouncement`. [#6760](https://github.com/mapbox/mapbox-navigation-android/pull/6760)
+- Fixed an issue where the first voice instruction might have been played twice. [#6766](https://github.com/mapbox/mapbox-navigation-android/pull/6766)
 
 ## Mapbox Navigation SDK 2.10.0-rc.1 - 16 December, 2022
 ### Changelog

libnavui-voice/src/main/java/com/mapbox/navigation/ui/voice/api/MapboxAudioGuidance.kt

@@ -14,7 +14,6 @@ import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
-import kotlinx.coroutines.FlowPreview
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.flow.Flow
@@ -25,9 +24,7 @@ import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.filter
 import kotlinx.coroutines.flow.first
-import kotlinx.coroutines.flow.flatMapConcat
 import kotlinx.coroutines.flow.flatMapLatest
-import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.updateAndGet
 import kotlinx.coroutines.launch
@@ -123,7 +120,7 @@ internal constructor(
     /**
      * Top level flow that will switch based on the language and muted state.
      */
-    @OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class)
+    @OptIn(ExperimentalCoroutinesApi::class)
     private fun audioGuidanceFlow(
         mapboxNavigation: MapboxNavigation
     ): Flow<MapboxAudioGuidanceState> {
@@ -146,18 +143,15 @@ internal constructor(
                 } else {
                     voiceInstructions
                         .filter { it.voiceInstructions != lastPlayedInstructions }
-                        .flatMapConcat {
+                        .map {
                             lastPlayedInstructions = it.voiceInstructions
                             val announcement = audioGuidance.speak(it.voiceInstructions)
-                            flowOf(announcement)
-                        }
-                        .map { speechAnnouncement ->
-                            internalStateFlow.updateAndGet {
+                            internalStateFlow.updateAndGet { state ->
                                 MapboxAudioGuidanceState(
-                                    isPlayable = it.isPlayable,
-                                    isMuted = it.isMuted,
-                                    voiceInstructions = it.voiceInstructions,
-                                    speechAnnouncement = speechAnnouncement
+                                    isPlayable = state.isPlayable,
+                                    isMuted = state.isMuted,
+                                    voiceInstructions = state.voiceInstructions,
+                                    speechAnnouncement = announcement
                                 )
                             }
                         }
@@ -195,7 +189,10 @@ internal constructor(
          * Construct an instance without registering to [MapboxNavigationApp].
          */
         @JvmStatic
-        fun create() = MapboxAudioGuidance(MapboxAudioGuidanceServices(), Dispatchers.Main)
+        fun create() = MapboxAudioGuidance(
+            MapboxAudioGuidanceServices(),
+            Dispatchers.Main.immediate
+        )
 
         /**
          * Get the registered instance or create one and register it to [MapboxNavigationApp].