Replace BroadcastChannel with MutableSharedFlow

Replace all usages of `ConflatedBroadcastChannel` and `BroadcastChannel` with `MutableSharedFlow`.
muzei · Oct 27, 2020 · 973b929 · 973b929
1 parent bbe075d
commit 973b929
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Showing 3 changed files with 24 additions and 19 deletions.
diff --git a/example-watchface/src/main/java/com/example/muzei/watchface/ArtworkImageLoader.kt b/example-watchface/src/main/java/com/example/muzei/watchface/ArtworkImageLoader.kt
@@ -24,11 +24,11 @@ import android.util.Size
 import com.google.android.apps.muzei.api.MuzeiContract
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.FlowPreview
-import kotlinx.coroutines.channels.ConflatedBroadcastChannel
+import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.channels.awaitClose
 import kotlinx.coroutines.channels.sendBlocking
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.asFlow
+import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.callbackFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.distinctUntilChanged
@@ -41,11 +41,13 @@ import java.io.FileNotFoundException
 @OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class)
 class ArtworkImageLoader(private val context: Context) {
 
-    private val requestedSizeChannel = ConflatedBroadcastChannel<Size?>(null)
+    private val requestSizeSharedFlow = MutableSharedFlow<Size?>(
+            replay = 1,
+            onBufferOverflow = BufferOverflow.DROP_OLDEST)
     var requestedSize: Size?
-        get() = requestedSizeChannel.value
+        get() = requestSizeSharedFlow.replayCache.firstOrNull()
         set(value) {
-            requestedSizeChannel.offer(value)
+            requestSizeSharedFlow.tryEmit(value)
         }
 
     private val unsizedArtworkFlow: Flow<Bitmap> = callbackFlow {
@@ -77,7 +79,7 @@ class ArtworkImageLoader(private val context: Context) {
     }
 
     val artworkFlow = unsizedArtworkFlow.combine(
-            requestedSizeChannel.asFlow().distinctUntilChanged()
+            requestSizeSharedFlow.distinctUntilChanged()
     ) { image, size ->
         // Resize the image to the specified size
         when {

diff --git a/main/src/main/java/com/google/android/apps/muzei/ArtDetailViewport.kt b/main/src/main/java/com/google/android/apps/muzei/ArtDetailViewport.kt
@@ -19,23 +19,24 @@ package com.google.android.apps.muzei
 import android.graphics.RectF
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.FlowPreview
-import kotlinx.coroutines.channels.BroadcastChannel
-import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.asFlow
+import kotlinx.coroutines.flow.MutableSharedFlow
 
 // Singleton that can be observed
 @OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class)
 object ArtDetailViewport {
     private val viewport0 = RectF()
     private val viewport1 = RectF()
-    private val broadcastChannel = BroadcastChannel<Boolean>(Channel.BUFFERED)
+    private val changes = MutableSharedFlow<Boolean>(
+            extraBufferCapacity = 1,
+            onBufferOverflow = BufferOverflow.DROP_OLDEST)
 
     /**
      * Get a [Flow] for listening for viewport change events.
      * The boolean indicates whether the change was triggered directly by a user interaction.
      */
-    fun getChanges(): Flow<Boolean> = broadcastChannel.asFlow()
+    fun getChanges(): Flow<Boolean> = changes
 
     fun getViewport(id: Int): RectF {
         return if (id == 0) viewport0 else viewport1
@@ -55,7 +56,7 @@ object ArtDetailViewport {
             isFromUser: Boolean = false
     ) {
         getViewport(id).set(left, top, right, bottom)
-        broadcastChannel.offer(isFromUser)
+        changes.tryEmit(isFromUser)
     }
 
     fun setDefaultViewport(
@@ -76,7 +77,7 @@ object ArtDetailViewport {
                     1f,
                     0.5f + bitmapAspectRatio / screenAspectRatio / 2f)
         }
-        broadcastChannel.offer(false)
+        changes.tryEmit(false)
         return this
     }
 }
diff --git a/main/src/main/java/com/google/android/apps/muzei/browse/BrowseProviderViewModel.kt b/main/src/main/java/com/google/android/apps/muzei/browse/BrowseProviderViewModel.kt
@@ -28,9 +28,9 @@ import com.google.android.apps.muzei.util.ContentProviderClientCompat
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.FlowPreview
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.channels.ConflatedBroadcastChannel
+import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.channels.awaitClose
-import kotlinx.coroutines.flow.asFlow
+import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.callbackFlow
 import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.flatMapLatest
@@ -43,11 +43,13 @@ class BrowseProviderViewModel(
         application: Application
 ): AndroidViewModel(application) {
 
-    private val contentUriChannel = ConflatedBroadcastChannel<Uri>()
+    private val contentUriSharedFlow = MutableSharedFlow<Uri>(
+            replay = 1,
+            onBufferOverflow = BufferOverflow.DROP_OLDEST)
     var contentUri: Uri
-        get() = contentUriChannel.value
+        get() = contentUriSharedFlow.replayCache.first()
         set(value) {
-            contentUriChannel.offer(value)
+            contentUriSharedFlow.tryEmit(value)
         }
 
     private fun getProviderArtwork(contentUri: Uri) = callbackFlow {
@@ -94,7 +96,7 @@ class BrowseProviderViewModel(
         }
     }
 
-    val artLiveData = contentUriChannel.asFlow().distinctUntilChanged()
+    val artLiveData = contentUriSharedFlow.distinctUntilChanged()
             .flatMapLatest { contentUri ->
                 getProviderArtwork(contentUri)
             }.asLiveData(viewModelScope.coroutineContext + EmptyCoroutineContext)