diff --git a/demos/cast/src/main/java/com/google/android/exoplayer2/castdemo/DefaultReceiverPlayerManager.java b/demos/cast/src/main/java/com/google/android/exoplayer2/castdemo/DefaultReceiverPlayerManager.java
index 4b71b3a001..fcee88ec49 100644
--- a/demos/cast/src/main/java/com/google/android/exoplayer2/castdemo/DefaultReceiverPlayerManager.java
+++ b/demos/cast/src/main/java/com/google/android/exoplayer2/castdemo/DefaultReceiverPlayerManager.java
@@ -255,7 +255,7 @@ import java.util.ArrayList;
   // Player.EventListener implementation.
 
   @Override
-  public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+  public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
     updateCurrentItemIndex();
   }
 
diff --git a/demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java b/demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java
index 35307eb5d8..8f46400670 100644
--- a/demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java
+++ b/demos/main/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java
@@ -627,7 +627,7 @@ public class PlayerActivity extends AppCompatActivity
   private class PlayerEventListener implements Player.EventListener {
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       if (playbackState == Player.STATE_ENDED) {
         showControls();
       }
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 14bb433d2b..390deac933 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
@@ -94,7 +94,7 @@ public final class CastPlayer extends BasePlayer {
   private CastTimeline currentTimeline;
   private TrackGroupArray currentTrackGroups;
   private TrackSelectionArray currentTrackSelection;
-  private int playbackState;
+  @Player.State private int playbackState;
   private int repeatMode;
   private int currentWindowIndex;
   private boolean playWhenReady;
@@ -305,6 +305,7 @@ public final class CastPlayer extends BasePlayer {
   }
 
   @Override
+  @Player.State
   public int getPlaybackState() {
     return playbackState;
   }
diff --git a/extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacPlaybackTest.java b/extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacPlaybackTest.java
index 1cd9483178..12ef68ee3c 100644
--- a/extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacPlaybackTest.java
+++ b/extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacPlaybackTest.java
@@ -101,7 +101,7 @@ public class FlacPlaybackTest {
     }
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       if (playbackState == Player.STATE_ENDED
           || (playbackState == Player.STATE_IDLE && playbackException != null)) {
         player.release();
diff --git a/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsLoader.java b/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsLoader.java
index 465ad51ac5..e860d07a14 100644
--- a/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsLoader.java
+++ b/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsLoader.java
@@ -963,7 +963,7 @@ public final class ImaAdsLoader
   }
 
   @Override
-  public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+  public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
     if (adsManager == null) {
       return;
     }
diff --git a/extensions/ima/src/test/java/com/google/android/exoplayer2/ext/ima/FakePlayer.java b/extensions/ima/src/test/java/com/google/android/exoplayer2/ext/ima/FakePlayer.java
index d20ccbd728..a9d6a37fac 100644
--- a/extensions/ima/src/test/java/com/google/android/exoplayer2/ext/ima/FakePlayer.java
+++ b/extensions/ima/src/test/java/com/google/android/exoplayer2/ext/ima/FakePlayer.java
@@ -31,7 +31,7 @@ import java.util.ArrayList;
   private final Timeline timeline;
 
   private boolean prepared;
-  private int state;
+  @Player.State private int state;
   private boolean playWhenReady;
   private long position;
   private long contentPosition;
@@ -96,8 +96,8 @@ import java.util.ArrayList;
     }
   }
 
-  /** Sets the state of this player with the given {@code STATE} constant. */
-  public void setState(int state, boolean playWhenReady) {
+  /** Sets the {@link Player.State} of this player. */
+  public void setState(@Player.State int state, boolean playWhenReady) {
     boolean notify = this.state != state || this.playWhenReady != playWhenReady;
     this.state = state;
     this.playWhenReady = playWhenReady;
@@ -131,6 +131,7 @@ import java.util.ArrayList;
   }
 
   @Override
+  @Player.State
   public int getPlaybackState() {
     return state;
   }
diff --git a/extensions/leanback/src/main/java/com/google/android/exoplayer2/ext/leanback/LeanbackPlayerAdapter.java b/extensions/leanback/src/main/java/com/google/android/exoplayer2/ext/leanback/LeanbackPlayerAdapter.java
index 3f4c5d6229..5705b73ab2 100644
--- a/extensions/leanback/src/main/java/com/google/android/exoplayer2/ext/leanback/LeanbackPlayerAdapter.java
+++ b/extensions/leanback/src/main/java/com/google/android/exoplayer2/ext/leanback/LeanbackPlayerAdapter.java
@@ -18,13 +18,13 @@ package com.google.android.exoplayer2.ext.leanback;
 import android.content.Context;
 import android.os.Handler;
 import androidx.annotation.Nullable;
+import android.util.Pair;
+import android.view.Surface;
+import android.view.SurfaceHolder;
 import androidx.leanback.R;
 import androidx.leanback.media.PlaybackGlueHost;
 import androidx.leanback.media.PlayerAdapter;
 import androidx.leanback.media.SurfaceHolderGlueHost;
-import android.util.Pair;
-import android.view.Surface;
-import android.view.SurfaceHolder;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ControlDispatcher;
 import com.google.android.exoplayer2.DefaultControlDispatcher;
@@ -271,7 +271,7 @@ public final class LeanbackPlayerAdapter extends PlayerAdapter implements Runnab
     // Player.EventListener implementation.
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       notifyStateChanged();
     }
 
diff --git a/extensions/mediasession/src/main/java/com/google/android/exoplayer2/ext/mediasession/MediaSessionConnector.java b/extensions/mediasession/src/main/java/com/google/android/exoplayer2/ext/mediasession/MediaSessionConnector.java
index 9c80fabc50..b922a2d0b8 100644
--- a/extensions/mediasession/src/main/java/com/google/android/exoplayer2/ext/mediasession/MediaSessionConnector.java
+++ b/extensions/mediasession/src/main/java/com/google/android/exoplayer2/ext/mediasession/MediaSessionConnector.java
@@ -994,7 +994,7 @@ public final class MediaSessionConnector {
     }
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       invalidateMediaSessionPlaybackState();
     }
 
diff --git a/extensions/opus/src/androidTest/java/com/google/android/exoplayer2/ext/opus/OpusPlaybackTest.java b/extensions/opus/src/androidTest/java/com/google/android/exoplayer2/ext/opus/OpusPlaybackTest.java
index dcd5f4957a..7c6835db0b 100644
--- a/extensions/opus/src/androidTest/java/com/google/android/exoplayer2/ext/opus/OpusPlaybackTest.java
+++ b/extensions/opus/src/androidTest/java/com/google/android/exoplayer2/ext/opus/OpusPlaybackTest.java
@@ -101,7 +101,7 @@ public class OpusPlaybackTest {
     }
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       if (playbackState == Player.STATE_ENDED
           || (playbackState == Player.STATE_IDLE && playbackException != null)) {
         player.release();
diff --git a/extensions/vp9/src/androidTest/java/com/google/android/exoplayer2/ext/vp9/VpxPlaybackTest.java b/extensions/vp9/src/androidTest/java/com/google/android/exoplayer2/ext/vp9/VpxPlaybackTest.java
index 5120004889..5ebeca68d0 100644
--- a/extensions/vp9/src/androidTest/java/com/google/android/exoplayer2/ext/vp9/VpxPlaybackTest.java
+++ b/extensions/vp9/src/androidTest/java/com/google/android/exoplayer2/ext/vp9/VpxPlaybackTest.java
@@ -139,7 +139,7 @@ public class VpxPlaybackTest {
     }
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       if (playbackState == Player.STATE_ENDED
           || (playbackState == Player.STATE_IDLE && playbackException != null)) {
         player.release();
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 96b9072c5c..bea7af189a 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
@@ -193,6 +193,7 @@ import java.util.concurrent.CopyOnWriteArrayList;
   }
 
   @Override
+  @Player.State
   public int getPlaybackState() {
     return playbackInfo.playbackState;
   }
@@ -658,7 +659,7 @@ import java.util.concurrent.CopyOnWriteArrayList;
   }
 
   private PlaybackInfo getResetPlaybackInfo(
-      boolean resetPosition, boolean resetState, int playbackState) {
+      boolean resetPosition, boolean resetState, @Player.State int playbackState) {
     if (resetPosition) {
       maskingWindowIndex = 0;
       maskingPeriodIndex = 0;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/PlaybackInfo.java b/library/core/src/main/java/com/google/android/exoplayer2/PlaybackInfo.java
index f45e61fb37..cf4643c5da 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/PlaybackInfo.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/PlaybackInfo.java
@@ -52,7 +52,7 @@ import com.google.android.exoplayer2.trackselection.TrackSelectorResult;
    */
   public final long contentPositionUs;
   /** The current playback state. One of the {@link Player}.STATE_ constants. */
-  public final int playbackState;
+  @Player.State public final int playbackState;
   /** Whether the player is currently loading. */
   public final boolean isLoading;
   /** The currently available track groups. */
@@ -128,7 +128,7 @@ import com.google.android.exoplayer2.trackselection.TrackSelectorResult;
       MediaPeriodId periodId,
       long startPositionUs,
       long contentPositionUs,
-      int playbackState,
+      @Player.State int playbackState,
       boolean isLoading,
       TrackGroupArray trackGroups,
       TrackSelectorResult trackSelectorResult,
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/Player.java b/library/core/src/main/java/com/google/android/exoplayer2/Player.java
index 8885be2e02..0e19212afa 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/Player.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/Player.java
@@ -361,9 +361,9 @@ public interface Player {
      * #getPlaybackState()} changes.
      *
      * @param playWhenReady Whether playback will proceed when ready.
-     * @param playbackState One of the {@code STATE} constants.
+     * @param playbackState The new {@link State playback state}.
      */
-    default void onPlayerStateChanged(boolean playWhenReady, int playbackState) {}
+    default void onPlayerStateChanged(boolean playWhenReady, @State int playbackState) {}
 
     /**
      * Called when the value of {@link #getRepeatMode()} changes.
@@ -443,6 +443,14 @@ public interface Player {
     }
   }
 
+  /**
+   * Playback state. One of {@link #STATE_IDLE}, {@link #STATE_BUFFERING}, {@link #STATE_READY} or
+   * {@link #STATE_ENDED}.
+   */
+  @Documented
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef({STATE_IDLE, STATE_BUFFERING, STATE_READY, STATE_ENDED})
+  @interface State {}
   /**
    * The player does not have any media to play.
    */
@@ -581,10 +589,11 @@ public interface Player {
   void removeListener(EventListener listener);
 
   /**
-   * Returns the current state of the player.
+   * Returns the current {@link State playback state} of the player.
    *
-   * @return One of the {@code STATE} constants defined in this interface.
+   * @return The current {@link State playback state}.
    */
+  @State
   int getPlaybackState();
 
   /**
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 910404a875..2ac71db44f 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
@@ -873,6 +873,7 @@ public class SimpleExoPlayer extends BasePlayer
   }
 
   @Override
+  @Player.State
   public int getPlaybackState() {
     verifyApplicationThread();
     return player.getPlaybackState();
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 c0d96e8e88..094024bc36 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
@@ -464,7 +464,7 @@ public class AnalyticsCollector
   }
 
   @Override
-  public final void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+  public final void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
     EventTime eventTime = generatePlayingMediaPeriodEventTime();
     for (AnalyticsListener listener : listeners) {
       listener.onPlayerStateChanged(eventTime, playWhenReady, playbackState);
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsListener.java b/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsListener.java
index 7f74216cc8..9a0339f5d4 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsListener.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/analytics/AnalyticsListener.java
@@ -127,10 +127,10 @@ public interface AnalyticsListener {
    *
    * @param eventTime The event time.
    * @param playWhenReady Whether the playback will proceed when ready.
-   * @param playbackState One of the {@link Player}.STATE constants.
+   * @param playbackState The new {@link Player.State playback state}.
    */
   default void onPlayerStateChanged(
-      EventTime eventTime, boolean playWhenReady, int playbackState) {}
+      EventTime eventTime, boolean playWhenReady, @Player.State int playbackState) {}
 
   /**
    * Called when the timeline changed.
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/util/EventLogger.java b/library/core/src/main/java/com/google/android/exoplayer2/util/EventLogger.java
index bb3dc8b83a..7a2ea5daf2 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/util/EventLogger.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/util/EventLogger.java
@@ -93,7 +93,8 @@ public class EventLogger implements AnalyticsListener {
   }
 
   @Override
-  public void onPlayerStateChanged(EventTime eventTime, boolean playWhenReady, int state) {
+  public void onPlayerStateChanged(
+      EventTime eventTime, boolean playWhenReady, @Player.State int state) {
     logd(eventTime, "state", playWhenReady + ", " + getStateString(state));
   }
 
diff --git a/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java b/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java
index 6d0627593f..639e80348b 100644
--- a/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java
+++ b/library/core/src/test/java/com/google/android/exoplayer2/ExoPlayerTest.java
@@ -509,7 +509,7 @@ public final class ExoPlayerTest {
           private int currentPlaybackState = Player.STATE_IDLE;
 
           @Override
-          public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+          public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
             currentPlaybackState = playbackState;
           }
 
@@ -2113,7 +2113,7 @@ public final class ExoPlayerTest {
     final EventListener eventListener1 =
         new EventListener() {
           @Override
-          public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+          public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
             eventListener1States.add(playbackState);
             if (playbackState == Player.STATE_READY) {
               playerReference.get().stop(/* reset= */ true);
@@ -2123,7 +2123,7 @@ public final class ExoPlayerTest {
     final EventListener eventListener2 =
         new EventListener() {
           @Override
-          public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+          public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
             eventListener2States.add(playbackState);
           }
         };
@@ -2170,7 +2170,7 @@ public final class ExoPlayerTest {
           }
 
           @Override
-          public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+          public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
             eventListenerPlayWhenReady.add(playWhenReady);
             eventListenerStates.add(playbackState);
             if (playbackState == Player.STATE_READY) {
@@ -2219,7 +2219,7 @@ public final class ExoPlayerTest {
     EventListener eventListener =
         new EventListener() {
           @Override
-          public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+          public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
             if (playbackState == Player.STATE_READY && clockAtStartMs.get() == C.TIME_UNSET) {
               clockAtStartMs.set(clock.elapsedRealtime());
             }
diff --git a/library/core/src/test/java/com/google/android/exoplayer2/analytics/AnalyticsCollectorTest.java b/library/core/src/test/java/com/google/android/exoplayer2/analytics/AnalyticsCollectorTest.java
index c455e39de6..2e9b539096 100644
--- a/library/core/src/test/java/com/google/android/exoplayer2/analytics/AnalyticsCollectorTest.java
+++ b/library/core/src/test/java/com/google/android/exoplayer2/analytics/AnalyticsCollectorTest.java
@@ -913,7 +913,7 @@ public final class AnalyticsCollectorTest {
 
     @Override
     public void onPlayerStateChanged(
-        EventTime eventTime, boolean playWhenReady, int playbackState) {
+        EventTime eventTime, boolean playWhenReady, @Player.State int playbackState) {
       reportedEvents.add(new ReportedEvent(EVENT_PLAYER_STATE_CHANGED, eventTime));
     }
 
diff --git a/library/ui/src/main/java/com/google/android/exoplayer2/ui/DebugTextViewHelper.java b/library/ui/src/main/java/com/google/android/exoplayer2/ui/DebugTextViewHelper.java
index da2081db31..0841296193 100644
--- a/library/ui/src/main/java/com/google/android/exoplayer2/ui/DebugTextViewHelper.java
+++ b/library/ui/src/main/java/com/google/android/exoplayer2/ui/DebugTextViewHelper.java
@@ -79,7 +79,7 @@ public class DebugTextViewHelper implements Player.EventListener, Runnable {
   // Player.EventListener implementation.
 
   @Override
-  public final void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+  public final void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
     updateAndPost();
   }
 
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 a5deb808c1..552774fe47 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
@@ -1130,7 +1130,7 @@ public class PlayerControlView extends FrameLayout {
     }
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       updatePlayPauseButton();
       updateProgress();
     }
diff --git a/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerNotificationManager.java b/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerNotificationManager.java
index 1dbd696b12..aa9e4b1492 100644
--- a/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerNotificationManager.java
+++ b/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerNotificationManager.java
@@ -1276,7 +1276,7 @@ public class PlayerNotificationManager {
   private class PlayerListener implements Player.EventListener {
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       if (wasPlayWhenReady != playWhenReady || lastPlaybackState != playbackState) {
         startOrUpdateNotification();
         wasPlayWhenReady = playWhenReady;
diff --git a/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerView.java b/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerView.java
index 06f0927a99..dde35e6e99 100644
--- a/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerView.java
+++ b/library/ui/src/main/java/com/google/android/exoplayer2/ui/PlayerView.java
@@ -1427,7 +1427,7 @@ public class PlayerView extends FrameLayout implements AdsLoader.AdViewProvider
     // Player.EventListener implementation
 
     @Override
-    public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+    public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
       updateBuffering();
       updateErrorMessage();
       if (isPlayingAd() && controllerHideDuringAds) {
diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/Action.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/Action.java
index f1fdfc42aa..facbe8bbde 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/Action.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/Action.java
@@ -669,7 +669,8 @@ public abstract class Action {
         player.addListener(
             new Player.EventListener() {
               @Override
-              public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+              public void onPlayerStateChanged(
+                  boolean playWhenReady, @Player.State int playbackState) {
                 if (targetPlaybackState == playbackState) {
                   player.removeListener(this);
                   nextAction.schedule(player, trackSelector, surface, handler);
diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoHostedTest.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoHostedTest.java
index 74c0d4bb43..90f2294bfc 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoHostedTest.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoHostedTest.java
@@ -183,7 +183,7 @@ public abstract class ExoHostedTest implements AnalyticsListener, HostedTest {
 
   @Override
   public final void onPlayerStateChanged(
-      EventTime eventTime, boolean playWhenReady, int playbackState) {
+      EventTime eventTime, boolean playWhenReady, @Player.State int playbackState) {
     Log.d(tag, "state [" + playWhenReady + ", " + playbackState + "]");
     playerWasPrepared |= playbackState != Player.STATE_IDLE;
     if (playbackState == Player.STATE_ENDED
diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoPlayerTestRunner.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoPlayerTestRunner.java
index 517f1ce2e7..0d55dd8530 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoPlayerTestRunner.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/ExoPlayerTestRunner.java
@@ -589,7 +589,7 @@ public final class ExoPlayerTestRunner implements Player.EventListener, ActionSc
   }
 
   @Override
-  public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
+  public void onPlayerStateChanged(boolean playWhenReady, @Player.State int playbackState) {
     playerWasPrepared |= playbackState != Player.STATE_IDLE;
     if (playbackState == Player.STATE_ENDED
         || (playbackState == Player.STATE_IDLE && playerWasPrepared)) {
diff --git a/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/StubExoPlayer.java b/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/StubExoPlayer.java
index a0d8c7f9d8..56de0a8b33 100644
--- a/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/StubExoPlayer.java
+++ b/testutils_robolectric/src/main/java/com/google/android/exoplayer2/testutil/StubExoPlayer.java
@@ -75,6 +75,7 @@ public abstract class StubExoPlayer extends BasePlayer implements ExoPlayer {
   }
 
   @Override
+  @Player.State
   public int getPlaybackState() {
     throw new UnsupportedOperationException();
   }