From 13e0513ea3efd6385d4cddbaca47a43807d486aa Mon Sep 17 00:00:00 2001
From: olly <olly@google.com>
Date: Tue, 23 Oct 2018 06:23:50 -0700
Subject: [PATCH] Give EventDispatcher more predictable behavior

If EventDispatcher.removeListener is called to remove a listener,
and if the call is made from the same thread that said listener
handles events on, then it should be guaranteed that the listener
will not be subsequently invoked on that thread.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=218331427
---
 .../exoplayer2/util/EventDispatcher.java      | 29 ++++++++++++++-----
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/library/core/src/main/java/com/google/android/exoplayer2/util/EventDispatcher.java b/library/core/src/main/java/com/google/android/exoplayer2/util/EventDispatcher.java
index 26c02d8ae9..07f278c808 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/util/EventDispatcher.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/util/EventDispatcher.java
@@ -39,22 +39,23 @@ public final class EventDispatcher<T> {
   /** The list of listeners and handlers. */
   private final CopyOnWriteArrayList<HandlerAndListener<T>> listeners;
 
-  /** Creates event dispatcher. */
+  /** Creates an event dispatcher. */
   public EventDispatcher() {
     listeners = new CopyOnWriteArrayList<>();
   }
 
-  /** Adds listener to event dispatcher. */
+  /** Adds a listener to the event dispatcher. */
   public void addListener(Handler handler, T eventListener) {
     Assertions.checkArgument(handler != null && eventListener != null);
     removeListener(eventListener);
     listeners.add(new HandlerAndListener<>(handler, eventListener));
   }
 
-  /** Removes listener from event dispatcher. */
+  /** Removes a listener from the event dispatcher. */
   public void removeListener(T eventListener) {
     for (HandlerAndListener<T> handlerAndListener : listeners) {
       if (handlerAndListener.listener == eventListener) {
+        handlerAndListener.release();
         listeners.remove(handlerAndListener);
       }
     }
@@ -67,19 +68,33 @@ public final class EventDispatcher<T> {
    */
   public void dispatch(Event<T> event) {
     for (HandlerAndListener<T> handlerAndListener : listeners) {
-      T eventListener = handlerAndListener.listener;
-      handlerAndListener.handler.post(() -> event.sendTo(eventListener));
+      handlerAndListener.dispatch(event);
     }
   }
 
   private static final class HandlerAndListener<T> {
 
-    public final Handler handler;
-    public final T listener;
+    private final Handler handler;
+    private final T listener;
+
+    private boolean released;
 
     public HandlerAndListener(Handler handler, T eventListener) {
       this.handler = handler;
       this.listener = eventListener;
     }
+
+    public void release() {
+      released = true;
+    }
+
+    public void dispatch(Event<T> event) {
+      handler.post(
+          () -> {
+            if (!released) {
+              event.sendTo(listener);
+            }
+          });
+    }
   }
 }