Enable re-preparing the `ImaSSAIMediaSource`

#minor-release

PiperOrigin-RevId: 538927855
(cherry picked from commit 499fd0942c7557bf5970b4bc79cd7fa4648f0227)

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

@@ -109,8 +109,6 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.List;
 import java.util.Map;
 import java.util.Map;
 import java.util.Objects;
 import java.util.Objects;
-import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
-import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 
 /** MediaSource for IMA server side inserted ad streams. */
 /** MediaSource for IMA server side inserted ad streams. */
 public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSource<Void> {
 public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSource<Void> {
@@ -518,7 +516,7 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
   @Nullable private StreamManager streamManager;
   @Nullable private StreamManager streamManager;
   @Nullable private ServerSideAdInsertionMediaSource serverSideAdInsertionMediaSource;
   @Nullable private ServerSideAdInsertionMediaSource serverSideAdInsertionMediaSource;
   @Nullable private IOException loadError;
   @Nullable private IOException loadError;
-  private @MonotonicNonNull Timeline contentTimeline;
+  @Nullable private Timeline contentTimeline;
   private AdPlaybackState adPlaybackState;
   private AdPlaybackState adPlaybackState;
 
 
   private ImaServerSideAdInsertionMediaSource(
   private ImaServerSideAdInsertionMediaSource(
@@ -633,6 +631,8 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
           });
           });
       loader = null;
       loader = null;
     }
     }
+    contentTimeline = null;
+    serverSideAdInsertionMediaSource = null;
   }
   }
 
 
   // Internal methods (called on the main thread).
   // Internal methods (called on the main thread).
@@ -680,7 +680,6 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
   }
   }
 
 
   @MainThread
   @MainThread
-  @EnsuresNonNull("this.contentTimeline")
   private void setContentTimeline(Timeline contentTimeline) {
   private void setContentTimeline(Timeline contentTimeline) {
     if (contentTimeline.equals(this.contentTimeline)) {
     if (contentTimeline.equals(this.contentTimeline)) {
       return;
       return;
@@ -698,6 +697,7 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
   @MainThread
   @MainThread
   private void invalidateServerSideAdInsertionAdPlaybackState() {
   private void invalidateServerSideAdInsertionAdPlaybackState() {
     if (!adPlaybackState.equals(AdPlaybackState.NONE) && contentTimeline != null) {
     if (!adPlaybackState.equals(AdPlaybackState.NONE) && contentTimeline != null) {
+      Timeline contentTimeline = checkNotNull(this.contentTimeline);
       ImmutableMap<Object, AdPlaybackState> splitAdPlaybackStates;
       ImmutableMap<Object, AdPlaybackState> splitAdPlaybackStates;
       if (Objects.equals(streamRequest.getFormat(), StreamFormat.DASH)) {
       if (Objects.equals(streamRequest.getFormat(), StreamFormat.DASH)) {
         // DASH ad groups are always split by period.
         // DASH ad groups are always split by period.
@@ -725,9 +725,7 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
   // Internal methods (called on the playback thread).
   // Internal methods (called on the playback thread).
 
 
   private void setContentUri(Uri contentUri) {
   private void setContentUri(Uri contentUri) {
-    if (serverSideAdInsertionMediaSource != null) {
-      return;
-    }
+    if (serverSideAdInsertionMediaSource == null) {
       MediaItem contentMediaItem =
       MediaItem contentMediaItem =
           new MediaItem.Builder()
           new MediaItem.Builder()
               .setUri(contentUri)
               .setUri(contentUri)
@@ -743,10 +741,12 @@ public final class ImaServerSideAdInsertionMediaSource extends CompositeMediaSou
       if (isLiveStream) {
       if (isLiveStream) {
         mainHandler.post(
         mainHandler.post(
             () ->
             () ->
-              setAdPlaybackState(new AdPlaybackState(adsId).withLivePostrollPlaceholderAppended()));
+                setAdPlaybackState(
+                    new AdPlaybackState(adsId).withLivePostrollPlaceholderAppended()));
       }
       }
       prepareChildSource(/* id= */ null, serverSideAdInsertionMediaSource);
       prepareChildSource(/* id= */ null, serverSideAdInsertionMediaSource);
     }
     }
+  }
 
 
   // Static methods.
   // Static methods.