Make ImaAdsLoader robust to calls after it's released

Issue: #3879

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=202100576

RELEASENOTES.md

@@ -47,6 +47,8 @@
   be directly made with the `Player.EventListener` interface.
 * Deprecate `DefaultAnalyticsListener` as selective listener overrides can be
   directly made with the `AnalyticsListener` interface.
+* IMA: Fix behavior when creating/releasing the player then releasing
+  `ImaAdsLoader` ((#3879)[https://github.com/google/ExoPlayer/issues/3879]).
 
 ### 2.8.2 ###
 

extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsLoader.java

@@ -281,13 +281,9 @@ public final class ImaAdsLoader
 
   /** The expected ad group index that IMA should load next. */
   private int expectedAdGroupIndex;
-  /**
+  /** The index of the current ad group that IMA is loading. */
-   * The index of the current ad group that IMA is loading.
-   */
   private int adGroupIndex;
-  /**
+  /** Whether IMA has sent an ad event to pause content since the last resume content event. */
-   * Whether IMA has sent an ad event to pause content since the last resume content event.
-   */
   private boolean imaPausedContent;
   /** The current ad playback state. */
   private @ImaAdState int imaAdState;
@@ -299,9 +295,7 @@ public final class ImaAdsLoader
 
   // Fields tracking the player/loader state.
 
-  /**
+  /** Whether the player is playing an ad. */
-   * Whether the player is playing an ad.
-   */
   private boolean playingAd;
   /**
    * If the player is playing an ad, stores the ad index in its ad group. {@link C#INDEX_UNSET}
@@ -324,13 +318,9 @@ public final class ImaAdsLoader
    * content progress should increase. {@link C#TIME_UNSET} otherwise.
    */
   private long fakeContentProgressOffsetMs;
-  /**
+  /** Stores the pending content position when a seek operation was intercepted to play an ad. */
-   * Stores the pending content position when a seek operation was intercepted to play an ad.
-   */
   private long pendingContentPositionMs;
-  /**
+  /** Whether {@link #getContentProgress()} has sent {@link #pendingContentPositionMs} to IMA. */
-   * Whether {@link #getContentProgress()} has sent {@link #pendingContentPositionMs} to IMA.
-   */
   private boolean sentPendingContentPositionMs;
 
   /**
@@ -526,6 +516,11 @@ public final class ImaAdsLoader
       adsManager.destroy();
       adsManager = null;
     }
+    imaPausedContent = false;
+    imaAdState = IMA_AD_STATE_NONE;
+    pendingAdLoadError = null;
+    adPlaybackState = AdPlaybackState.NONE;
+    updateAdPlaybackState();
   }
 
   @Override
@@ -575,7 +570,7 @@ public final class ImaAdsLoader
       Log.d(TAG, "onAdEvent: " + adEventType);
     }
     if (adsManager == null) {
-      Log.w(TAG, "Dropping ad event after release: " + adEvent);
+      Log.w(TAG, "Ignoring AdEvent after release: " + adEvent);
       return;
     }
     try {
@@ -671,6 +666,13 @@ public final class ImaAdsLoader
   @Override
   public void loadAd(String adUriString) {
     try {
+      if (DEBUG) {
+        Log.d(TAG, "loadAd in ad group " + adGroupIndex);
+      }
+      if (adsManager == null) {
+        Log.w(TAG, "Ignoring loadAd after release");
+        return;
+      }
       if (adGroupIndex == C.INDEX_UNSET) {
         Log.w(
             TAG,
@@ -679,9 +681,6 @@ public final class ImaAdsLoader
         adGroupIndex = expectedAdGroupIndex;
         adsManager.start();
       }
-      if (DEBUG) {
-        Log.d(TAG, "loadAd in ad group " + adGroupIndex);
-      }
       int adIndexInAdGroup = getAdIndexInAdGroupToLoad(adGroupIndex);
       if (adIndexInAdGroup == C.INDEX_UNSET) {
         Log.w(TAG, "Unexpected loadAd in an ad group with no remaining unavailable ads");
@@ -710,6 +709,10 @@ public final class ImaAdsLoader
     if (DEBUG) {
       Log.d(TAG, "playAd");
     }
+    if (adsManager == null) {
+      Log.w(TAG, "Ignoring playAd after release");
+      return;
+    }
     switch (imaAdState) {
       case IMA_AD_STATE_PLAYING:
         // IMA does not always call stopAd before resuming content.
@@ -753,6 +756,10 @@ public final class ImaAdsLoader
     if (DEBUG) {
       Log.d(TAG, "stopAd");
     }
+    if (adsManager == null) {
+      Log.w(TAG, "Ignoring stopAd after release");
+      return;
+    }
     if (player == null) {
       // Sometimes messages from IMA arrive after detaching the player. See [Internal: b/63801642].
       Log.w(TAG, "Unexpected stopAd while detached");
@@ -1099,6 +1106,10 @@ public final class ImaAdsLoader
       Log.d(
           TAG, "Prepare error for ad " + adIndexInAdGroup + " in group " + adGroupIndex, exception);
     }
+    if (adsManager == null) {
+      Log.w(TAG, "Ignoring ad prepare error after release");
+      return;
+    }
     if (imaAdState == IMA_AD_STATE_NONE) {
       // Send IMA a content position at the ad group so that it will try to play it, at which point
       // we can notify that it failed to load.
@@ -1181,7 +1192,7 @@ public final class ImaAdsLoader
     Log.e(TAG, message, cause);
     // We can't recover from an unexpected error in general, so skip all remaining ads.
     if (adPlaybackState == null) {
-      adPlaybackState = new AdPlaybackState();
+      adPlaybackState = AdPlaybackState.NONE;
     } else {
       for (int i = 0; i < adPlaybackState.adGroupCount; i++) {
         adPlaybackState = adPlaybackState.withSkippedAdGroup(i);