Support multiple DefaultDrmSessionManager listeners.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=190236842

RELEASENOTES.md

@@ -33,6 +33,7 @@
   * Add release method to Cache interface.
   * Prevent multiple instances of SimpleCache in the same folder.
     Previous instance must be released.
+* DRM: Allow multiple listeners for `DefaultDrmSessionManager`.
 * Fix ANR issue on Redmi 4X and Redmi Note 4
   ([#4006](https://github.com/google/ExoPlayer/issues/4006)).
 * Removed default renderer time offset of 60000000 from internal player. The

demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java

@@ -432,8 +432,11 @@ public class PlayerActivity extends Activity
             keyRequestPropertiesArray[i + 1]);
       }
     }
-    return new DefaultDrmSessionManager<>(uuid, FrameworkMediaDrm.newInstance(uuid), drmCallback,
+    DefaultDrmSessionManager<FrameworkMediaCrypto> drmSessionManager =
-        null, mainHandler, eventLogger, multiSession);
+        new DefaultDrmSessionManager<>(
+            uuid, FrameworkMediaDrm.newInstance(uuid), drmCallback, null, multiSession);
+    drmSessionManager.addListener(mainHandler, eventLogger);
+    return drmSessionManager;
   }
 
   private void releasePlayer() {

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSession.java

@@ -25,6 +25,7 @@ import android.os.Message;
 import android.util.Log;
 import android.util.Pair;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.drm.DefaultDrmSessionEventListener.EventDispatcher;
 import com.google.android.exoplayer2.drm.ExoMediaDrm.DefaultKeyRequest;
 import com.google.android.exoplayer2.drm.ExoMediaDrm.KeyRequest;
 import com.google.android.exoplayer2.drm.ExoMediaDrm.ProvisionRequest;
@@ -80,8 +81,7 @@ import java.util.UUID;
   private final String mimeType;
   private final @DefaultDrmSessionManager.Mode int mode;
   private final HashMap<String, String> optionalKeyRequestParameters;
-  private final Handler eventHandler;
+  private final EventDispatcher eventDispatcher;
-  private final DefaultDrmSessionManager.EventListener eventListener;
   private final int initialDrmRequestRetryCount;
 
   /* package */ final MediaDrmCallback callback;
@@ -109,17 +109,22 @@ import java.util.UUID;
    * @param optionalKeyRequestParameters The optional key request parameters.
    * @param callback The media DRM callback.
    * @param playbackLooper The playback looper.
-   * @param eventHandler The handler to post listener events.
+   * @param eventDispatcher The dispatcher for DRM session manager events.
-   * @param eventListener The DRM session manager event listener.
    * @param initialDrmRequestRetryCount The number of times to retry for initial provisioning and
    *     key request before reporting error.
    */
-  public DefaultDrmSession(UUID uuid, ExoMediaDrm<T> mediaDrm,
+  public DefaultDrmSession(
-      ProvisioningManager<T> provisioningManager, byte[] initData, String mimeType,
+      UUID uuid,
-      @DefaultDrmSessionManager.Mode int mode, byte[] offlineLicenseKeySetId,
+      ExoMediaDrm<T> mediaDrm,
-      HashMap<String, String> optionalKeyRequestParameters, MediaDrmCallback callback,
+      ProvisioningManager<T> provisioningManager,
-      Looper playbackLooper, Handler eventHandler,
+      byte[] initData,
-      DefaultDrmSessionManager.EventListener eventListener,
+      String mimeType,
+      @DefaultDrmSessionManager.Mode int mode,
+      byte[] offlineLicenseKeySetId,
+      HashMap<String, String> optionalKeyRequestParameters,
+      MediaDrmCallback callback,
+      Looper playbackLooper,
+      EventDispatcher eventDispatcher,
       int initialDrmRequestRetryCount) {
     this.uuid = uuid;
     this.provisioningManager = provisioningManager;
@@ -129,9 +134,7 @@ import java.util.UUID;
     this.optionalKeyRequestParameters = optionalKeyRequestParameters;
     this.callback = callback;
     this.initialDrmRequestRetryCount = initialDrmRequestRetryCount;
-
+    this.eventDispatcher = eventDispatcher;
-    this.eventHandler = eventHandler;
-    this.eventListener = eventListener;
     state = STATE_OPENING;
 
     postResponseHandler = new PostResponseHandler(playbackLooper);
@@ -306,14 +309,7 @@ import java.util.UUID;
             onError(new KeysExpiredException());
           } else {
             state = STATE_OPENED_WITH_KEYS;
-            if (eventHandler != null && eventListener != null) {
+            eventDispatcher.drmKeysRestored();
-              eventHandler.post(new Runnable() {
-                @Override
-                public void run() {
-                  eventListener.onDrmKeysRestored();
-                }
-              });
-            }
           }
         }
         break;
@@ -391,14 +387,7 @@ import java.util.UUID;
       }
       if (mode == DefaultDrmSessionManager.MODE_RELEASE) {
         mediaDrm.provideKeyResponse(offlineLicenseKeySetId, responseData);
-        if (eventHandler != null && eventListener != null) {
+        eventDispatcher.drmKeysRemoved();
-          eventHandler.post(new Runnable() {
-            @Override
-            public void run() {
-              eventListener.onDrmKeysRemoved();
-            }
-          });
-        }
       } else {
         byte[] keySetId = mediaDrm.provideKeyResponse(sessionId, responseData);
         if ((mode == DefaultDrmSessionManager.MODE_DOWNLOAD
@@ -407,14 +396,7 @@ import java.util.UUID;
           offlineLicenseKeySetId = keySetId;
         }
         state = STATE_OPENED_WITH_KEYS;
-        if (eventHandler != null && eventListener != null) {
+        eventDispatcher.drmKeysLoaded();
-          eventHandler.post(new Runnable() {
-            @Override
-            public void run() {
-              eventListener.onDrmKeysLoaded();
-            }
-          });
-        }
       }
     } catch (Exception e) {
       onKeysError(e);
@@ -438,14 +420,7 @@ import java.util.UUID;
 
   private void onError(final Exception e) {
     lastException = new DrmSessionException(e);
-    if (eventHandler != null && eventListener != null) {
+    eventDispatcher.drmSessionManagerError(e);
-      eventHandler.post(new Runnable() {
-        @Override
-        public void run() {
-          eventListener.onDrmSessionManagerError(e);
-        }
-      });
-    }
     if (state != STATE_OPENED_WITH_KEYS) {
       state = STATE_ERROR;
     }

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSessionEventListener.java

@@ -0,0 +1,139 @@
+/*
+ * 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 com.google.android.exoplayer2.drm;
+
+import android.os.Handler;
+import com.google.android.exoplayer2.Player;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/** Listener of {@link DefaultDrmSessionManager} events. */
+public interface DefaultDrmSessionEventListener {
+
+  /** Called each time keys are loaded. */
+  void onDrmKeysLoaded();
+
+  /**
+   * Called when a drm error occurs.
+   *
+   * <p>This method being called does not indicate that playback has failed, or that it will fail.
+   * The player may be able to recover from the error and continue. Hence applications should
+   * <em>not</em> implement this method to display a user visible error or initiate an application
+   * level retry ({@link Player.EventListener#onPlayerError} is the appropriate place to implement
+   * such behavior). This method is called to provide the application with an opportunity to log the
+   * error if it wishes to do so.
+   *
+   * @param error The corresponding exception.
+   */
+  void onDrmSessionManagerError(Exception error);
+
+  /** Called each time offline keys are restored. */
+  void onDrmKeysRestored();
+
+  /** Called each time offline keys are removed. */
+  void onDrmKeysRemoved();
+
+  /** Dispatches drm events to all registered listeners. */
+  final class EventDispatcher {
+
+    private final CopyOnWriteArrayList<HandlerAndListener> listeners;
+
+    /** Creates event dispatcher. */
+    public EventDispatcher() {
+      listeners = new CopyOnWriteArrayList<>();
+    }
+
+    /** Adds listener to event dispatcher. */
+    public void addListener(Handler handler, DefaultDrmSessionEventListener eventListener) {
+      listeners.add(new HandlerAndListener(handler, eventListener));
+    }
+
+    /** Removes listener from event dispatcher. */
+    public void removeListener(DefaultDrmSessionEventListener eventListener) {
+      for (HandlerAndListener handlerAndListener : listeners) {
+        if (handlerAndListener.listener == eventListener) {
+          listeners.remove(handlerAndListener);
+        }
+      }
+    }
+
+    /** Dispatches {@link DefaultDrmSessionEventListener#onDrmKeysLoaded()}. */
+    public void drmKeysLoaded() {
+      for (HandlerAndListener handlerAndListener : listeners) {
+        final DefaultDrmSessionEventListener listener = handlerAndListener.listener;
+        handlerAndListener.handler.post(
+            new Runnable() {
+              @Override
+              public void run() {
+                listener.onDrmKeysLoaded();
+              }
+            });
+      }
+    }
+
+    /** Dispatches {@link DefaultDrmSessionEventListener#onDrmSessionManagerError(Exception)}. */
+    public void drmSessionManagerError(final Exception e) {
+      for (HandlerAndListener handlerAndListener : listeners) {
+        final DefaultDrmSessionEventListener listener = handlerAndListener.listener;
+        handlerAndListener.handler.post(
+            new Runnable() {
+              @Override
+              public void run() {
+                listener.onDrmSessionManagerError(e);
+              }
+            });
+      }
+    }
+
+    /** Dispatches {@link DefaultDrmSessionEventListener#onDrmKeysRestored()}. */
+    public void drmKeysRestored() {
+      for (HandlerAndListener handlerAndListener : listeners) {
+        final DefaultDrmSessionEventListener listener = handlerAndListener.listener;
+        handlerAndListener.handler.post(
+            new Runnable() {
+              @Override
+              public void run() {
+                listener.onDrmKeysRestored();
+              }
+            });
+      }
+    }
+
+    /** Dispatches {@link DefaultDrmSessionEventListener#onDrmKeysRemoved()}. */
+    public void drmKeysRemoved() {
+      for (HandlerAndListener handlerAndListener : listeners) {
+        final DefaultDrmSessionEventListener listener = handlerAndListener.listener;
+        handlerAndListener.handler.post(
+            new Runnable() {
+              @Override
+              public void run() {
+                listener.onDrmKeysRemoved();
+              }
+            });
+      }
+    }
+
+    private static final class HandlerAndListener {
+
+      public final Handler handler;
+      public final DefaultDrmSessionEventListener listener;
+
+      public HandlerAndListener(Handler handler, DefaultDrmSessionEventListener eventListener) {
+        this.handler = handler;
+        this.listener = eventListener;
+      }
+    }
+  }
+}

library/core/src/main/java/com/google/android/exoplayer2/drm/DefaultDrmSessionManager.java

@@ -25,8 +25,8 @@ import android.support.annotation.NonNull;
 import android.text.TextUtils;
 import android.util.Log;
 import com.google.android.exoplayer2.C;
-import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.drm.DefaultDrmSession.ProvisioningManager;
+import com.google.android.exoplayer2.drm.DefaultDrmSessionEventListener.EventDispatcher;
 import com.google.android.exoplayer2.drm.DrmInitData.SchemeData;
 import com.google.android.exoplayer2.drm.DrmSession.DrmSessionException;
 import com.google.android.exoplayer2.drm.ExoMediaDrm.OnEventListener;
@@ -48,41 +48,9 @@ import java.util.UUID;
 public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSessionManager<T>,
     ProvisioningManager<T> {
 
-  /**
+  /** @deprecated Use {@link DefaultDrmSessionEventListener}. */
-   * Listener of {@link DefaultDrmSessionManager} events.
+  @Deprecated
-   */
+  public interface EventListener extends DefaultDrmSessionEventListener {}
-  public interface EventListener {
-
-    /**
-     * Called each time keys are loaded.
-     */
-    void onDrmKeysLoaded();
-
-    /**
-     * Called when a drm error occurs.
-     * <p>
-     * This method being called does not indicate that playback has failed, or that it will fail.
-     * The player may be able to recover from the error and continue. Hence applications should
-     * <em>not</em> implement this method to display a user visible error or initiate an application
-     * level retry ({@link Player.EventListener#onPlayerError} is the appropriate place to implement
-     * such behavior). This method is called to provide the application with an opportunity to log
-     * the error if it wishes to do so.
-     *
-     * @param e The corresponding exception.
-     */
-    void onDrmSessionManagerError(Exception e);
-
-    /**
-     * Called each time offline keys are restored.
-     */
-    void onDrmKeysRestored();
-
-    /**
-     * Called each time offline keys are removed.
-     */
-    void onDrmKeysRemoved();
-
-  }
 
   /**
    * Signals that the {@link DrmInitData} passed to {@link #acquireSession} does not contain does
@@ -127,8 +95,7 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
   private final ExoMediaDrm<T> mediaDrm;
   private final MediaDrmCallback callback;
   private final HashMap<String, String> optionalKeyRequestParameters;
-  private final Handler eventHandler;
+  private final EventDispatcher eventDispatcher;
-  private final EventListener eventListener;
   private final boolean multiSession;
   private final int initialDrmRequestRetryCount;
 
@@ -141,40 +108,66 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
 
   /* package */ volatile MediaDrmHandler mediaDrmHandler;
 
+  /**
+   * @deprecated Use {@link #newWidevineInstance(MediaDrmCallback, HashMap)} and {@link
+   *     #addListener(Handler, DefaultDrmSessionEventListener)}.
+   */
+  @Deprecated
+  public static DefaultDrmSessionManager<FrameworkMediaCrypto> newWidevineInstance(
+      MediaDrmCallback callback,
+      HashMap<String, String> optionalKeyRequestParameters,
+      Handler eventHandler,
+      DefaultDrmSessionEventListener eventListener)
+      throws UnsupportedDrmException {
+    DefaultDrmSessionManager<FrameworkMediaCrypto> drmSessionManager =
+        newWidevineInstance(callback, optionalKeyRequestParameters);
+    drmSessionManager.addListener(eventHandler, eventListener);
+    return drmSessionManager;
+  }
+
   /**
    * Instantiates a new instance using the Widevine scheme.
    *
    * @param callback Performs key and provisioning requests.
    * @param optionalKeyRequestParameters An optional map of parameters to pass as the last argument
    *     to {@link ExoMediaDrm#getKeyRequest(byte[], byte[], String, int, HashMap)}. May be null.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
    * @throws UnsupportedDrmException If the specified DRM scheme is not supported.
    */
   public static DefaultDrmSessionManager<FrameworkMediaCrypto> newWidevineInstance(
-      MediaDrmCallback callback, HashMap<String, String> optionalKeyRequestParameters,
+      MediaDrmCallback callback, HashMap<String, String> optionalKeyRequestParameters)
-      Handler eventHandler, EventListener eventListener) throws UnsupportedDrmException {
+      throws UnsupportedDrmException {
-    return newFrameworkInstance(C.WIDEVINE_UUID, callback, optionalKeyRequestParameters,
+    return newFrameworkInstance(C.WIDEVINE_UUID, callback, optionalKeyRequestParameters);
-        eventHandler, eventListener);
+  }
+
+  /**
+   * @deprecated Use {@link #newPlayReadyInstance(MediaDrmCallback, String)} and {@link
+   *     #addListener(Handler, DefaultDrmSessionEventListener)}.
+   */
+  @Deprecated
+  public static DefaultDrmSessionManager<FrameworkMediaCrypto> newPlayReadyInstance(
+      MediaDrmCallback callback,
+      String customData,
+      Handler eventHandler,
+      DefaultDrmSessionEventListener eventListener)
+      throws UnsupportedDrmException {
+    DefaultDrmSessionManager<FrameworkMediaCrypto> drmSessionManager =
+        newPlayReadyInstance(callback, customData);
+    drmSessionManager.addListener(eventHandler, eventListener);
+    return drmSessionManager;
   }
 
   /**
    * Instantiates a new instance using the PlayReady scheme.
-   * <p>
+   *
-   * Note that PlayReady is unsupported by most Android devices, with the exception of Android TV
+   * <p>Note that PlayReady is unsupported by most Android devices, with the exception of Android TV
    * devices, which do provide support.
    *
    * @param callback Performs key and provisioning requests.
    * @param customData Optional custom data to include in requests generated by the instance.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
    * @throws UnsupportedDrmException If the specified DRM scheme is not supported.
    */
   public static DefaultDrmSessionManager<FrameworkMediaCrypto> newPlayReadyInstance(
-      MediaDrmCallback callback, String customData, Handler eventHandler,
+      MediaDrmCallback callback, String customData) throws UnsupportedDrmException {
-      EventListener eventListener) throws UnsupportedDrmException {
     HashMap<String, String> optionalKeyRequestParameters;
     if (!TextUtils.isEmpty(customData)) {
       optionalKeyRequestParameters = new HashMap<>();
@@ -182,8 +175,25 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
     } else {
       optionalKeyRequestParameters = null;
     }
-    return newFrameworkInstance(C.PLAYREADY_UUID, callback, optionalKeyRequestParameters,
+    return newFrameworkInstance(C.PLAYREADY_UUID, callback, optionalKeyRequestParameters);
-        eventHandler, eventListener);
+  }
+
+  /**
+   * @deprecated Use {@link #newFrameworkInstance(UUID, MediaDrmCallback, HashMap)} and {@link
+   *     #addListener(Handler, DefaultDrmSessionEventListener)}.
+   */
+  @Deprecated
+  public static DefaultDrmSessionManager<FrameworkMediaCrypto> newFrameworkInstance(
+      UUID uuid,
+      MediaDrmCallback callback,
+      HashMap<String, String> optionalKeyRequestParameters,
+      Handler eventHandler,
+      DefaultDrmSessionEventListener eventListener)
+      throws UnsupportedDrmException {
+    DefaultDrmSessionManager<FrameworkMediaCrypto> drmSessionManager =
+        newFrameworkInstance(uuid, callback, optionalKeyRequestParameters);
+    drmSessionManager.addListener(eventHandler, eventListener);
+    return drmSessionManager;
   }
 
   /**
@@ -193,34 +203,72 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
    * @param callback Performs key and provisioning requests.
    * @param optionalKeyRequestParameters An optional map of parameters to pass as the last argument
    *     to {@link ExoMediaDrm#getKeyRequest(byte[], byte[], String, int, HashMap)}. May be null.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
    * @throws UnsupportedDrmException If the specified DRM scheme is not supported.
    */
   public static DefaultDrmSessionManager<FrameworkMediaCrypto> newFrameworkInstance(
-      UUID uuid, MediaDrmCallback callback, HashMap<String, String> optionalKeyRequestParameters,
+      UUID uuid, MediaDrmCallback callback, HashMap<String, String> optionalKeyRequestParameters)
-      Handler eventHandler, EventListener eventListener) throws UnsupportedDrmException {
+      throws UnsupportedDrmException {
-    return new DefaultDrmSessionManager<>(uuid, FrameworkMediaDrm.newInstance(uuid), callback,
+    return new DefaultDrmSessionManager<>(
-        optionalKeyRequestParameters, eventHandler, eventListener, false,
+        uuid,
+        FrameworkMediaDrm.newInstance(uuid),
+        callback,
+        optionalKeyRequestParameters,
+        /* multiSession= */ false,
         INITIAL_DRM_REQUEST_RETRY_COUNT);
   }
 
   /**
-   * @param uuid The UUID of the drm scheme.
+   * @deprecated Use {@link #DefaultDrmSessionManager(UUID, ExoMediaDrm, MediaDrmCallback, HashMap)}
-   * @param mediaDrm An underlying {@link ExoMediaDrm} for use by the manager.
+   *     and {@link #addListener(Handler, DefaultDrmSessionEventListener)}.
-   * @param callback Performs key and provisioning requests.
-   * @param optionalKeyRequestParameters An optional map of parameters to pass as the last argument
-   *     to {@link ExoMediaDrm#getKeyRequest(byte[], byte[], String, int, HashMap)}. May be null.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
    */
-  public DefaultDrmSessionManager(UUID uuid, ExoMediaDrm<T> mediaDrm, MediaDrmCallback callback,
+  @Deprecated
-      HashMap<String, String> optionalKeyRequestParameters, Handler eventHandler,
+  public DefaultDrmSessionManager(
-      EventListener eventListener) {
+      UUID uuid,
-    this(uuid, mediaDrm, callback, optionalKeyRequestParameters, eventHandler, eventListener,
+      ExoMediaDrm<T> mediaDrm,
-        false, INITIAL_DRM_REQUEST_RETRY_COUNT);
+      MediaDrmCallback callback,
+      HashMap<String, String> optionalKeyRequestParameters,
+      Handler eventHandler,
+      DefaultDrmSessionEventListener eventListener) {
+    this(uuid, mediaDrm, callback, optionalKeyRequestParameters);
+    addListener(eventHandler, eventListener);
+  }
+
+  /**
+   * @param uuid The UUID of the drm scheme.
+   * @param mediaDrm An underlying {@link ExoMediaDrm} for use by the manager.
+   * @param callback Performs key and provisioning requests.
+   * @param optionalKeyRequestParameters An optional map of parameters to pass as the last argument
+   *     to {@link ExoMediaDrm#getKeyRequest(byte[], byte[], String, int, HashMap)}. May be null.
+   */
+  public DefaultDrmSessionManager(
+      UUID uuid,
+      ExoMediaDrm<T> mediaDrm,
+      MediaDrmCallback callback,
+      HashMap<String, String> optionalKeyRequestParameters) {
+    this(
+        uuid,
+        mediaDrm,
+        callback,
+        optionalKeyRequestParameters,
+        /* multiSession= */ false,
+        INITIAL_DRM_REQUEST_RETRY_COUNT);
+  }
+
+  /**
+   * @deprecated Use {@link #DefaultDrmSessionManager(UUID, ExoMediaDrm, MediaDrmCallback, HashMap,
+   *     boolean)} and {@link #addListener(Handler, DefaultDrmSessionEventListener)}.
+   */
+  @Deprecated
+  public DefaultDrmSessionManager(
+      UUID uuid,
+      ExoMediaDrm<T> mediaDrm,
+      MediaDrmCallback callback,
+      HashMap<String, String> optionalKeyRequestParameters,
+      Handler eventHandler,
+      DefaultDrmSessionEventListener eventListener,
+      boolean multiSession) {
+    this(uuid, mediaDrm, callback, optionalKeyRequestParameters, multiSession);
+    addListener(eventHandler, eventListener);
   }
 
   /**
@@ -229,17 +277,46 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
    * @param callback Performs key and provisioning requests.
    * @param optionalKeyRequestParameters An optional map of parameters to pass as the last argument
    *     to {@link ExoMediaDrm#getKeyRequest(byte[], byte[], String, int, HashMap)}. May be null.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
    * @param multiSession A boolean that specify whether multiple key session support is enabled.
    *     Default is false.
    */
-  public DefaultDrmSessionManager(UUID uuid, ExoMediaDrm<T> mediaDrm, MediaDrmCallback callback,
+  public DefaultDrmSessionManager(
-      HashMap<String, String> optionalKeyRequestParameters, Handler eventHandler,
+      UUID uuid,
-      EventListener eventListener, boolean multiSession) {
+      ExoMediaDrm<T> mediaDrm,
-    this(uuid, mediaDrm, callback, optionalKeyRequestParameters, eventHandler, eventListener,
+      MediaDrmCallback callback,
-        multiSession, INITIAL_DRM_REQUEST_RETRY_COUNT);
+      HashMap<String, String> optionalKeyRequestParameters,
+      boolean multiSession) {
+    this(
+        uuid,
+        mediaDrm,
+        callback,
+        optionalKeyRequestParameters,
+        multiSession,
+        INITIAL_DRM_REQUEST_RETRY_COUNT);
+  }
+
+  /**
+   * @deprecated Use {@link #DefaultDrmSessionManager(UUID, ExoMediaDrm, MediaDrmCallback, HashMap,
+   *     boolean, int)} and {@link #addListener(Handler, DefaultDrmSessionEventListener)}.
+   */
+  @Deprecated
+  public DefaultDrmSessionManager(
+      UUID uuid,
+      ExoMediaDrm<T> mediaDrm,
+      MediaDrmCallback callback,
+      HashMap<String, String> optionalKeyRequestParameters,
+      Handler eventHandler,
+      DefaultDrmSessionEventListener eventListener,
+      boolean multiSession,
+      int initialDrmRequestRetryCount) {
+    this(
+        uuid,
+        mediaDrm,
+        callback,
+        optionalKeyRequestParameters,
+        multiSession,
+        initialDrmRequestRetryCount);
+    addListener(eventHandler, eventListener);
   }
 
   /**
@@ -248,17 +325,18 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
    * @param callback Performs key and provisioning requests.
    * @param optionalKeyRequestParameters An optional map of parameters to pass as the last argument
    *     to {@link ExoMediaDrm#getKeyRequest(byte[], byte[], String, int, HashMap)}. May be null.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
    * @param multiSession A boolean that specify whether multiple key session support is enabled.
    *     Default is false.
    * @param initialDrmRequestRetryCount The number of times to retry for initial provisioning and
    *     key request before reporting error.
    */
-  public DefaultDrmSessionManager(UUID uuid, ExoMediaDrm<T> mediaDrm, MediaDrmCallback callback,
+  public DefaultDrmSessionManager(
-      HashMap<String, String> optionalKeyRequestParameters, Handler eventHandler,
+      UUID uuid,
-      EventListener eventListener, boolean multiSession, int initialDrmRequestRetryCount) {
+      ExoMediaDrm<T> mediaDrm,
+      MediaDrmCallback callback,
+      HashMap<String, String> optionalKeyRequestParameters,
+      boolean multiSession,
+      int initialDrmRequestRetryCount) {
     Assertions.checkNotNull(uuid);
     Assertions.checkNotNull(mediaDrm);
     Assertions.checkArgument(!C.COMMON_PSSH_UUID.equals(uuid), "Use C.CLEARKEY_UUID instead");
@@ -266,8 +344,7 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
     this.mediaDrm = mediaDrm;
     this.callback = callback;
     this.optionalKeyRequestParameters = optionalKeyRequestParameters;
-    this.eventHandler = eventHandler;
+    this.eventDispatcher = new EventDispatcher();
-    this.eventListener = eventListener;
     this.multiSession = multiSession;
     this.initialDrmRequestRetryCount = initialDrmRequestRetryCount;
     mode = MODE_PLAYBACK;
@@ -279,6 +356,25 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
     mediaDrm.setOnEventListener(new MediaDrmEventListener());
   }
 
+  /**
+   * Adds a {@link DefaultDrmSessionEventListener} to listen to drm session events.
+   *
+   * @param handler A handler to use when delivering events to {@code eventListener}.
+   * @param eventListener A listener of events.
+   */
+  public final void addListener(Handler handler, DefaultDrmSessionEventListener eventListener) {
+    eventDispatcher.addListener(handler, eventListener);
+  }
+
+  /**
+   * Removes a {@link DefaultDrmSessionEventListener} from the list of drm session event listeners.
+   *
+   * @param eventListener The listener to remove.
+   */
+  public final void removeListener(DefaultDrmSessionEventListener eventListener) {
+    eventDispatcher.removeListener(eventListener);
+  }
+
   /**
    * Provides access to {@link ExoMediaDrm#getPropertyString(String)}.
    * <p>
@@ -406,15 +502,7 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
       SchemeData data = getSchemeData(drmInitData, uuid, false);
       if (data == null) {
         final MissingSchemeDataException error = new MissingSchemeDataException(uuid);
-        if (eventHandler != null && eventListener != null) {
+        eventDispatcher.drmSessionManagerError(error);
-          eventHandler.post(
-              new Runnable() {
-                @Override
-                public void run() {
-                  eventListener.onDrmSessionManagerError(error);
-                }
-              });
-        }
         return new ErrorStateDrmSession<>(new DrmSessionException(error));
       }
       initData = getSchemeInitData(data, uuid);
@@ -437,9 +525,20 @@ public class DefaultDrmSessionManager<T extends ExoMediaCrypto> implements DrmSe
 
     if (session == null) {
       // Create a new session.
-      session = new DefaultDrmSession<>(uuid, mediaDrm, this, initData, mimeType, mode,
+      session =
-          offlineLicenseKeySetId, optionalKeyRequestParameters, callback, playbackLooper,
+          new DefaultDrmSession<>(
-          eventHandler, eventListener, initialDrmRequestRetryCount);
+              uuid,
+              mediaDrm,
+              this,
+              initData,
+              mimeType,
+              mode,
+              offlineLicenseKeySetId,
+              optionalKeyRequestParameters,
+              callback,
+              playbackLooper,
+              eventDispatcher,
+              initialDrmRequestRetryCount);
       sessions.add(session);
     }
     session.acquire();

library/core/src/main/java/com/google/android/exoplayer2/drm/OfflineLicenseHelper.java

@@ -21,7 +21,6 @@ import android.os.Handler;
 import android.os.HandlerThread;
 import android.util.Pair;
 import com.google.android.exoplayer2.C;
-import com.google.android.exoplayer2.drm.DefaultDrmSessionManager.EventListener;
 import com.google.android.exoplayer2.drm.DefaultDrmSessionManager.Mode;
 import com.google.android.exoplayer2.drm.DrmSession.DrmSessionException;
 import com.google.android.exoplayer2.upstream.HttpDataSource;
@@ -90,10 +89,12 @@ public final class OfflineLicenseHelper<T extends ExoMediaCrypto> {
    * @throws UnsupportedDrmException If the Widevine DRM scheme is unsupported or cannot be
    *     instantiated.
    * @see DefaultDrmSessionManager#DefaultDrmSessionManager(java.util.UUID, ExoMediaDrm,
-   *     MediaDrmCallback, HashMap, Handler, EventListener)
+   *     MediaDrmCallback, HashMap, Handler, DefaultDrmSessionEventListener)
    */
   public static OfflineLicenseHelper<FrameworkMediaCrypto> newWidevineInstance(
-      String defaultLicenseUrl, boolean forceDefaultLicenseUrl, Factory httpDataSourceFactory,
+      String defaultLicenseUrl,
+      boolean forceDefaultLicenseUrl,
+      Factory httpDataSourceFactory,
       HashMap<String, String> optionalKeyRequestParameters)
       throws UnsupportedDrmException {
     return new OfflineLicenseHelper<>(C.WIDEVINE_UUID,
@@ -111,36 +112,41 @@ public final class OfflineLicenseHelper<T extends ExoMediaCrypto> {
    * @param optionalKeyRequestParameters An optional map of parameters to pass as the last argument
    *     to {@link MediaDrm#getKeyRequest(byte[], byte[], String, int, HashMap)}. May be null.
    * @see DefaultDrmSessionManager#DefaultDrmSessionManager(java.util.UUID, ExoMediaDrm,
-   *     MediaDrmCallback, HashMap, Handler, EventListener)
+   *     MediaDrmCallback, HashMap, Handler, DefaultDrmSessionEventListener)
    */
-  public OfflineLicenseHelper(UUID uuid, ExoMediaDrm<T> mediaDrm, MediaDrmCallback callback,
+  public OfflineLicenseHelper(
+      UUID uuid,
+      ExoMediaDrm<T> mediaDrm,
+      MediaDrmCallback callback,
       HashMap<String, String> optionalKeyRequestParameters) {
     handlerThread = new HandlerThread("OfflineLicenseHelper");
     handlerThread.start();
     conditionVariable = new ConditionVariable();
-    EventListener eventListener = new EventListener() {
+    DefaultDrmSessionEventListener eventListener =
-      @Override
+        new DefaultDrmSessionEventListener() {
-      public void onDrmKeysLoaded() {
+          @Override
-        conditionVariable.open();
+          public void onDrmKeysLoaded() {
-      }
+            conditionVariable.open();
+          }
 
-      @Override
+          @Override
-      public void onDrmSessionManagerError(Exception e) {
+          public void onDrmSessionManagerError(Exception e) {
-        conditionVariable.open();
+            conditionVariable.open();
-      }
+          }
 
-      @Override
+          @Override
-      public void onDrmKeysRestored() {
+          public void onDrmKeysRestored() {
-        conditionVariable.open();
+            conditionVariable.open();
-      }
+          }
 
-      @Override
+          @Override
-      public void onDrmKeysRemoved() {
+          public void onDrmKeysRemoved() {
-        conditionVariable.open();
+            conditionVariable.open();
-      }
+          }
-    };
+        };
-    drmSessionManager = new DefaultDrmSessionManager<>(uuid, mediaDrm, callback,
+    drmSessionManager =
-        optionalKeyRequestParameters, new Handler(handlerThread.getLooper()), eventListener);
+        new DefaultDrmSessionManager<>(uuid, mediaDrm, callback, optionalKeyRequestParameters);
+    drmSessionManager.addListener(new Handler(handlerThread.getLooper()), eventListener);
   }
 
   /**

library/core/src/main/java/com/google/android/exoplayer2/util/EventLogger.java

@@ -27,7 +27,7 @@ import com.google.android.exoplayer2.RendererCapabilities;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.audio.AudioRendererEventListener;
 import com.google.android.exoplayer2.decoder.DecoderCounters;
-import com.google.android.exoplayer2.drm.DefaultDrmSessionManager;
+import com.google.android.exoplayer2.drm.DefaultDrmSessionEventListener;
 import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.metadata.MetadataOutput;
 import com.google.android.exoplayer2.metadata.emsg.EventMessage;
@@ -60,7 +60,7 @@ public class EventLogger
         VideoRendererEventListener,
         MediaSourceEventListener,
         AdsMediaSource.EventListener,
-        DefaultDrmSessionManager.EventListener {
+        DefaultDrmSessionEventListener {
 
   private static final String TAG = "EventLogger";
   private static final int MAX_TIMELINE_ITEM_LINES = 3;

playbacktests/src/androidTest/java/com/google/android/exoplayer2/playbacktests/gts/DashTestRunner.java

@@ -279,7 +279,7 @@ public final class DashTestRunner {
         MediaDrmCallback drmCallback = new HttpMediaDrmCallback(widevineLicenseUrl,
             new DefaultHttpDataSourceFactory(userAgent));
         DefaultDrmSessionManager<FrameworkMediaCrypto> drmSessionManager =
-            DefaultDrmSessionManager.newWidevineInstance(drmCallback, null, null, null);
+            DefaultDrmSessionManager.newWidevineInstance(drmCallback, null);
         if (!useL1Widevine) {
           drmSessionManager.setPropertyString(
               SECURITY_LEVEL_PROPERTY, WIDEVINE_SECURITY_LEVEL_3);