diff --git a/demos/main/src/main/java/com/google/android/exoplayer2/demo/DownloadTracker.java b/demos/main/src/main/java/com/google/android/exoplayer2/demo/DownloadTracker.java
index 7522ba0499..a57d402d63 100644
--- a/demos/main/src/main/java/com/google/android/exoplayer2/demo/DownloadTracker.java
+++ b/demos/main/src/main/java/com/google/android/exoplayer2/demo/DownloadTracker.java
@@ -76,6 +76,7 @@ public class DownloadTracker {
   }
 
   public void addListener(Listener listener) {
+    checkNotNull(listener);
     listeners.add(listener);
   }
 
diff --git a/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastPlayer.java b/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastPlayer.java
index 957001fe74..6e74e8325f 100644
--- a/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastPlayer.java
+++ b/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastPlayer.java
@@ -291,6 +291,7 @@ public final class CastPlayer extends BasePlayer {
 
   @Override
   public void addListener(EventListener listener) {
+    Assertions.checkNotNull(listener);
     listeners.addIfAbsent(new ListenerHolder(listener));
   }
 
diff --git a/extensions/media2/src/main/java/com/google/android/exoplayer2/ext/media2/SettableFuture.java b/extensions/media2/src/main/java/com/google/android/exoplayer2/ext/media2/SettableFuture.java
index 01a30682ae..d8a8c1f5a4 100644
--- a/extensions/media2/src/main/java/com/google/android/exoplayer2/ext/media2/SettableFuture.java
+++ b/extensions/media2/src/main/java/com/google/android/exoplayer2/ext/media2/SettableFuture.java
@@ -51,6 +51,8 @@ import java.util.concurrent.atomic.AtomicReference;
 
   @Override
   public void addListener(Runnable listener, Executor executor) {
+    Assertions.checkNotNull(listener);
+    Assertions.checkNotNull(executor);
     future.addListener(listener, executor);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java
index a7479d349b..2cc423be34 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java
@@ -254,6 +254,7 @@ import java.util.concurrent.TimeoutException;
 
   @Override
   public void addListener(Player.EventListener listener) {
+    Assertions.checkNotNull(listener);
     listeners.addIfAbsent(new ListenerHolder(listener));
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java b/library/core/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java
index b7fb3a89ea..9607c59a28 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java
@@ -820,6 +820,7 @@ public class SimpleExoPlayer extends BasePlayer
   @Override
   public void addAudioListener(AudioListener listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
+    Assertions.checkNotNull(listener);
     audioListeners.add(listener);
   }
 
@@ -970,6 +971,7 @@ public class SimpleExoPlayer extends BasePlayer
    */
   public void addAnalyticsListener(AnalyticsListener listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
+    Assertions.checkNotNull(listener);
     analyticsCollector.addListener(listener);
   }
 
@@ -1068,6 +1070,7 @@ public class SimpleExoPlayer extends BasePlayer
   @Override
   public void addVideoListener(com.google.android.exoplayer2.video.VideoListener listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
+    Assertions.checkNotNull(listener);
     videoListeners.add(listener);
   }
 
@@ -1121,7 +1124,7 @@ public class SimpleExoPlayer extends BasePlayer
    */
   @Deprecated
   @SuppressWarnings("deprecation")
-  public void setVideoListener(VideoListener listener) {
+  public void setVideoListener(@Nullable VideoListener listener) {
     videoListeners.clear();
     if (listener != null) {
       addVideoListener(listener);
@@ -1144,6 +1147,7 @@ public class SimpleExoPlayer extends BasePlayer
   @Override
   public void addTextOutput(TextOutput listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
+    Assertions.checkNotNull(listener);
     textOutputs.add(listener);
   }
 
@@ -1187,6 +1191,7 @@ public class SimpleExoPlayer extends BasePlayer
   @Override
   public void addMetadataOutput(MetadataOutput listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
+    Assertions.checkNotNull(listener);
     metadataOutputs.add(listener);
   }
 
@@ -1227,7 +1232,7 @@ public class SimpleExoPlayer extends BasePlayer
    */
   @Deprecated
   @SuppressWarnings("deprecation")
-  public void setVideoDebugListener(VideoRendererEventListener listener) {
+  public void setVideoDebugListener(@Nullable VideoRendererEventListener listener) {
     videoDebugListeners.retainAll(Collections.singleton(analyticsCollector));
     if (listener != null) {
       addVideoDebugListener(listener);
@@ -1240,6 +1245,7 @@ public class SimpleExoPlayer extends BasePlayer
    */
   @Deprecated
   public void addVideoDebugListener(VideoRendererEventListener listener) {
+    Assertions.checkNotNull(listener);
     videoDebugListeners.add(listener);
   }
 
@@ -1258,7 +1264,7 @@ public class SimpleExoPlayer extends BasePlayer
    */
   @Deprecated
   @SuppressWarnings("deprecation")
-  public void setAudioDebugListener(AudioRendererEventListener listener) {
+  public void setAudioDebugListener(@Nullable AudioRendererEventListener listener) {
     audioDebugListeners.retainAll(Collections.singleton(analyticsCollector));
     if (listener != null) {
       addAudioDebugListener(listener);
@@ -1271,6 +1277,7 @@ public class SimpleExoPlayer extends BasePlayer
    */
   @Deprecated
   public void addAudioDebugListener(AudioRendererEventListener listener) {
+    Assertions.checkNotNull(listener);
     audioDebugListeners.add(listener);
   }
 
@@ -1298,6 +1305,7 @@ public class SimpleExoPlayer extends BasePlayer
   @Override
   public void addListener(Player.EventListener listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
+    Assertions.checkNotNull(listener);
     player.addListener(listener);
   }
 
@@ -1866,6 +1874,7 @@ public class SimpleExoPlayer extends BasePlayer
   @Override
   public void addDeviceListener(DeviceListener listener) {
     // Don't verify application thread. We allow calls to this method from any thread.
+    Assertions.checkNotNull(listener);
     deviceListeners.add(listener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java b/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java
index 694f2bc8c1..743b415f09 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsCollector.java
@@ -101,6 +101,7 @@ public class AnalyticsCollector
    * @param listener The listener to add.
    */
   public void addListener(AnalyticsListener listener) {
+    Assertions.checkNotNull(listener);
     listeners.add(listener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadManager.java b/library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadManager.java
index 6b12ab3759..edb9995b60 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadManager.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadManager.java
@@ -324,6 +324,7 @@ public final class DownloadManager {
    * @param listener The listener to be added.
    */
   public void addListener(Listener listener) {
+    Assertions.checkNotNull(listener);
     listeners.add(listener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/BaseMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/BaseMediaSource.java
index 04b8ad1f83..96ef4b0c6d 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/BaseMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/BaseMediaSource.java
@@ -162,6 +162,8 @@ public abstract class BaseMediaSource implements MediaSource {
 
   @Override
   public final void addEventListener(Handler handler, MediaSourceEventListener eventListener) {
+    Assertions.checkNotNull(handler);
+    Assertions.checkNotNull(eventListener);
     eventDispatcher.addEventListener(handler, eventListener);
   }
 
@@ -172,6 +174,8 @@ public abstract class BaseMediaSource implements MediaSource {
 
   @Override
   public final void addDrmEventListener(Handler handler, DrmSessionEventListener eventListener) {
+    Assertions.checkNotNull(handler);
+    Assertions.checkNotNull(eventListener);
     drmEventDispatcher.addEventListener(handler, eventListener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/IcyDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/IcyDataSource.java
index 84d2902c53..04fe67b119 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/IcyDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/IcyDataSource.java
@@ -67,6 +67,7 @@ import java.util.Map;
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    Assertions.checkNotNull(transferListener);
     upstream.addTransferListener(transferListener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/BandwidthMeter.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/BandwidthMeter.java
index 8fefb50a96..d520fcfa60 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/BandwidthMeter.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/BandwidthMeter.java
@@ -56,10 +56,11 @@ public interface BandwidthMeter {
       }
 
       /** Adds a listener to the event dispatcher. */
-      public void addListener(Handler handler, BandwidthMeter.EventListener eventListener) {
-        Assertions.checkArgument(handler != null && eventListener != null);
+      public void addListener(Handler eventHandler, BandwidthMeter.EventListener eventListener) {
+        Assertions.checkNotNull(eventHandler);
+        Assertions.checkNotNull(eventListener);
         removeListener(eventListener);
-        listeners.add(new HandlerAndListener(handler, eventListener));
+        listeners.add(new HandlerAndListener(eventHandler, eventListener));
       }
 
       /** Removes a listener from the event dispatcher. */
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java
index 80687db31f..ce6243eda0 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/BaseDataSource.java
@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.upstream;
 
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
 import static com.google.android.exoplayer2.util.Util.castNonNull;
 
 import androidx.annotation.Nullable;
@@ -47,6 +48,7 @@ public abstract class BaseDataSource implements DataSource {
 
   @Override
   public final void addTransferListener(TransferListener transferListener) {
+    checkNotNull(transferListener);
     if (!listeners.contains(transferListener)) {
       listeners.add(transferListener);
       listenerCount++;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultBandwidthMeter.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultBandwidthMeter.java
index 66aec96e89..2d62bdbf95 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultBandwidthMeter.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultBandwidthMeter.java
@@ -332,6 +332,8 @@ public final class DefaultBandwidthMeter implements BandwidthMeter, TransferList
 
   @Override
   public void addEventListener(Handler eventHandler, EventListener eventListener) {
+    Assertions.checkNotNull(eventHandler);
+    Assertions.checkNotNull(eventListener);
     eventDispatcher.addListener(eventHandler, eventListener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultDataSource.java
index 98026c4677..afef3e6761 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/DefaultDataSource.java
@@ -135,6 +135,7 @@ public final class DefaultDataSource implements DataSource {
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    Assertions.checkNotNull(transferListener);
     baseDataSource.addTransferListener(transferListener);
     transferListeners.add(transferListener);
     maybeAddListenerToDataSource(fileDataSource, transferListener);
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/PriorityDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/PriorityDataSource.java
index 767b6d78a3..e52e1db376 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/PriorityDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/PriorityDataSource.java
@@ -55,6 +55,7 @@ public final class PriorityDataSource implements DataSource {
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    Assertions.checkNotNull(transferListener);
     upstream.addTransferListener(transferListener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/ResolvingDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/ResolvingDataSource.java
index f5fb67e40e..958780cbc3 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/ResolvingDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/ResolvingDataSource.java
@@ -15,6 +15,8 @@
  */
 package com.google.android.exoplayer2.upstream;
 
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
+
 import android.net.Uri;
 import androidx.annotation.Nullable;
 import java.io.IOException;
@@ -95,6 +97,7 @@ public final class ResolvingDataSource implements DataSource {
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    checkNotNull(transferListener);
     upstreamDataSource.addTransferListener(transferListener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/StatsDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/StatsDataSource.java
index 6cdc381ba2..4340169f45 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/StatsDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/StatsDataSource.java
@@ -72,6 +72,7 @@ public final class StatsDataSource implements DataSource {
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    Assertions.checkNotNull(transferListener);
     dataSource.addTransferListener(transferListener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/TeeDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/TeeDataSource.java
index f56f19a6ca..689273d388 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/TeeDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/TeeDataSource.java
@@ -45,6 +45,7 @@ public final class TeeDataSource implements DataSource {
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    Assertions.checkNotNull(transferListener);
     upstream.addTransferListener(transferListener);
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
index 7398ff58a2..e1ec63161a 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/CacheDataSource.java
@@ -541,6 +541,7 @@ public final class CacheDataSource implements DataSource {
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    Assertions.checkNotNull(transferListener);
     cacheReadDataSource.addTransferListener(transferListener);
     upstreamDataSource.addTransferListener(transferListener);
   }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java
index 17655fa312..29c09ff486 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/cache/SimpleCache.java
@@ -309,6 +309,8 @@ public final class SimpleCache implements Cache {
   @Override
   public synchronized NavigableSet<CacheSpan> addListener(String key, Listener listener) {
     Assertions.checkState(!released);
+    Assertions.checkNotNull(key);
+    Assertions.checkNotNull(listener);
     ArrayList<Listener> listenersForKey = listeners.get(key);
     if (listenersForKey == null) {
       listenersForKey = new ArrayList<>();
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/upstream/crypto/AesCipherDataSource.java b/library/core/src/main/java/com/google/android/exoplayer2/upstream/crypto/AesCipherDataSource.java
index 665a47191e..5abe42b937 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/upstream/crypto/AesCipherDataSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/upstream/crypto/AesCipherDataSource.java
@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.upstream.crypto;
 
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
 import static com.google.android.exoplayer2.util.Util.castNonNull;
 
 import android.net.Uri;
@@ -45,6 +46,7 @@ public final class AesCipherDataSource implements DataSource {
 
   @Override
   public void addTransferListener(TransferListener transferListener) {
+    checkNotNull(transferListener);
     upstream.addTransferListener(transferListener);
   }
 
diff --git a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/Aes128DataSource.java b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/Aes128DataSource.java
index fe70298dc8..11d68b1c08 100644
--- a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/Aes128DataSource.java
+++ b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/Aes128DataSource.java
@@ -66,6 +66,7 @@ import javax.crypto.spec.SecretKeySpec;
 
   @Override
   public final void addTransferListener(TransferListener transferListener) {
+    Assertions.checkNotNull(transferListener);
     upstream.addTransferListener(transferListener);
   }
 
diff --git a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTracker.java b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTracker.java
index 02d2718dec..1ad75dac1e 100644
--- a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTracker.java
+++ b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTracker.java
@@ -161,6 +161,7 @@ public final class DefaultHlsPlaylistTracker
 
   @Override
   public void addListener(PlaylistEventListener listener) {
+    Assertions.checkNotNull(listener);
     listeners.add(listener);
   }
 
diff --git a/library/ui/src/main/java/com/google/android/exoplayer2/ui/DefaultTimeBar.java b/library/ui/src/main/java/com/google/android/exoplayer2/ui/DefaultTimeBar.java
index 44c0035278..24d890134a 100644
--- a/library/ui/src/main/java/com/google/android/exoplayer2/ui/DefaultTimeBar.java
+++ b/library/ui/src/main/java/com/google/android/exoplayer2/ui/DefaultTimeBar.java
@@ -450,6 +450,7 @@ public class DefaultTimeBar extends View implements TimeBar {
 
   @Override
   public void addListener(OnScrubListener listener) {
+    Assertions.checkNotNull(listener);
     listeners.add(listener);
   }
 
diff --git a/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerControlView.java b/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerControlView.java
index 4b9de374c3..62e9094cf0 100644
--- a/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerControlView.java
+++ b/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerControlView.java
@@ -586,6 +586,7 @@ public class PlayerControlView extends FrameLayout {
    * @param listener The listener to be notified about visibility changes.
    */
   public void addVisibilityListener(VisibilityListener listener) {
+    Assertions.checkNotNull(listener);
     visibilityListeners.add(listener);
   }
 
diff --git a/library/ui/src/main/java/com/google/android/exoplayer2/ui/StyledPlayerControlView.java b/library/ui/src/main/java/com/google/android/exoplayer2/ui/StyledPlayerControlView.java
index a33a508d89..0d51f94661 100644
--- a/library/ui/src/main/java/com/google/android/exoplayer2/ui/StyledPlayerControlView.java
+++ b/library/ui/src/main/java/com/google/android/exoplayer2/ui/StyledPlayerControlView.java
@@ -790,6 +790,7 @@ public class StyledPlayerControlView extends FrameLayout {
    * @param listener The listener to be notified about visibility changes.
    */
   public void addVisibilityListener(VisibilityListener listener) {
+    Assertions.checkNotNull(listener);
     visibilityListeners.add(listener);
   }