1 files changed, 100 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/util/EventDispatcher.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/util/EventDispatcher.java
new file mode 100644
index 0000000000..6e9a3798bf
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/util/EventDispatcher.java
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.mozilla.thirdparty.com.google.android.exoplayer2.util;
+
+import android.os.Handler;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * Event dispatcher which allows listener registration.
+ *
+ * @param <T> The type of listener.
+ */
+public final class EventDispatcher<T> {
+
+  /** Functional interface to send an event. */
+  public interface Event<T> {
+
+    /**
+     * Sends the event to a listener.
+     *
+     * @param listener The listener to send the event to.
+     */
+    void sendTo(T listener);
+  }
+
+  /** The list of listeners and handlers. */
+  private final CopyOnWriteArrayList<HandlerAndListener<T>> listeners;
+
+  /** Creates an event dispatcher. */
+  public EventDispatcher() {
+    listeners = new CopyOnWriteArrayList<>();
+  }
+
+  /** 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 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);
+      }
+    }
+  }
+
+  /**
+   * Dispatches an event to all registered listeners.
+   *
+   * @param event The {@link Event}.
+   */
+  public void dispatch(Event<T> event) {
+    for (HandlerAndListener<T> handlerAndListener : listeners) {
+      handlerAndListener.dispatch(event);
+    }
+  }
+
+  private static final class HandlerAndListener<T> {
+
+    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);
+            }
+          });
+    }
+  }
+}