Add method (dispatchEvent) to MediaSourceEventListener.EventDispatcher to allow invoking subclassed listeners

RELEASENOTES.md

@@ -45,6 +45,9 @@
         overriding this method in `DefaultLoadControl`). The default
         implementation of `LoadControl` disables preloading in case an app is
         using a custom implementation of `LoadControl`.
+    *   Add method `MediaSourceEventListener.EventDispatcher.dispatchEvent()` to
+        allow invoking events of subclass listeners
+        ([1736](https://github.com/androidx/media/pull/1736)).
 *   Transformer:
 *   Track Selection:
 *   Extractors:

libraries/exoplayer/src/main/java/androidx/media3/exoplayer/source/MediaSourceEventListener.java

@@ -26,6 +26,7 @@
 import androidx.media3.common.Format;
 import androidx.media3.common.Player;
 import androidx.media3.common.util.Assertions;
+import androidx.media3.common.util.Consumer;
 import androidx.media3.common.util.UnstableApi;
 import androidx.media3.exoplayer.source.MediaSource.MediaPeriodId;
 import java.io.IOException;
@@ -259,12 +260,9 @@ public void loadStarted(
 
     /** Dispatches {@link #onLoadStarted(int, MediaPeriodId, LoadEventInfo, MediaLoadData)}. */
     public void loadStarted(LoadEventInfo loadEventInfo, MediaLoadData mediaLoadData) {
-      for (ListenerAndHandler listenerAndHandler : listenerAndHandlers) {
-        MediaSourceEventListener listener = listenerAndHandler.listener;
-        postOrRun(
-            listenerAndHandler.handler,
-            () -> listener.onLoadStarted(windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData));
-      }
+      dispatchEvent(
+          (listener) ->
+              listener.onLoadStarted(windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData));
     }
 
     /** Dispatches {@link #onLoadCompleted(int, MediaPeriodId, LoadEventInfo, MediaLoadData)}. */
@@ -304,13 +302,9 @@ public void loadCompleted(
 
     /** Dispatches {@link #onLoadCompleted(int, MediaPeriodId, LoadEventInfo, MediaLoadData)}. */
     public void loadCompleted(LoadEventInfo loadEventInfo, MediaLoadData mediaLoadData) {
-      for (ListenerAndHandler listenerAndHandler : listenerAndHandlers) {
-        MediaSourceEventListener listener = listenerAndHandler.listener;
-        postOrRun(
-            listenerAndHandler.handler,
-            () ->
-                listener.onLoadCompleted(windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData));
-      }
+      dispatchEvent(
+          (listener) ->
+              listener.onLoadCompleted(windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData));
     }
 
     /** Dispatches {@link #onLoadCanceled(int, MediaPeriodId, LoadEventInfo, MediaLoadData)}. */
@@ -350,13 +344,9 @@ public void loadCanceled(
 
     /** Dispatches {@link #onLoadCanceled(int, MediaPeriodId, LoadEventInfo, MediaLoadData)}. */
     public void loadCanceled(LoadEventInfo loadEventInfo, MediaLoadData mediaLoadData) {
-      for (ListenerAndHandler listenerAndHandler : listenerAndHandlers) {
-        MediaSourceEventListener listener = listenerAndHandler.listener;
-        postOrRun(
-            listenerAndHandler.handler,
-            () ->
-                listener.onLoadCanceled(windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData));
-      }
+      dispatchEvent(
+          (listener) ->
+              listener.onLoadCanceled(windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData));
     }
 
     /**
@@ -419,14 +409,10 @@ public void loadError(
         MediaLoadData mediaLoadData,
         IOException error,
         boolean wasCanceled) {
-      for (ListenerAndHandler listenerAndHandler : listenerAndHandlers) {
-        MediaSourceEventListener listener = listenerAndHandler.listener;
-        postOrRun(
-            listenerAndHandler.handler,
-            () ->
-                listener.onLoadError(
-                    windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData, error, wasCanceled));
-      }
+      dispatchEvent(
+          (listener) ->
+              listener.onLoadError(
+                  windowIndex, mediaPeriodId, loadEventInfo, mediaLoadData, error, wasCanceled));
     }
 
     /** Dispatches {@link #onUpstreamDiscarded(int, MediaPeriodId, MediaLoadData)}. */
@@ -445,12 +431,8 @@ public void upstreamDiscarded(int trackType, long mediaStartTimeUs, long mediaEn
     /** Dispatches {@link #onUpstreamDiscarded(int, MediaPeriodId, MediaLoadData)}. */
     public void upstreamDiscarded(MediaLoadData mediaLoadData) {
       MediaPeriodId mediaPeriodId = Assertions.checkNotNull(this.mediaPeriodId);
-      for (ListenerAndHandler listenerAndHandler : listenerAndHandlers) {
-        MediaSourceEventListener listener = listenerAndHandler.listener;
-        postOrRun(
-            listenerAndHandler.handler,
-            () -> listener.onUpstreamDiscarded(windowIndex, mediaPeriodId, mediaLoadData));
-      }
+      dispatchEvent(
+          (listener) -> listener.onUpstreamDiscarded(windowIndex, mediaPeriodId, mediaLoadData));
     }
 
     /** Dispatches {@link #onDownstreamFormatChanged(int, MediaPeriodId, MediaLoadData)}. */
@@ -473,11 +455,16 @@ public void downstreamFormatChanged(
 
     /** Dispatches {@link #onDownstreamFormatChanged(int, MediaPeriodId, MediaLoadData)}. */
     public void downstreamFormatChanged(MediaLoadData mediaLoadData) {
+      dispatchEvent(
+          (listener) ->
+              listener.onDownstreamFormatChanged(windowIndex, mediaPeriodId, mediaLoadData));
+    }
+
+    /** Dispatches to a function that supplies a {@link MediaSourceEventListener}. */
+    public void dispatchEvent(Consumer<MediaSourceEventListener> event) {
       for (ListenerAndHandler listenerAndHandler : listenerAndHandlers) {
         MediaSourceEventListener listener = listenerAndHandler.listener;
-        postOrRun(
-            listenerAndHandler.handler,
-            () -> listener.onDownstreamFormatChanged(windowIndex, mediaPeriodId, mediaLoadData));
+        postOrRun(listenerAndHandler.handler, () -> event.accept(listener));
       }
     }