Make HlsMediaSource.Factory take a factory of trackers instead of an instance

This allows creating multiple HLS media sources from a single Factory, as
required by the interface.

Issue:#4814

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213297850

RELEASENOTES.md

@@ -40,6 +40,8 @@
     ([#4422](https://github.com/google/ExoPlayer/issues/4422)).
   * Fix the bitrate being unset on primary track sample formats
     ([#3297](https://github.com/google/ExoPlayer/issues/3297)).
+  * Make `HlsMediaSource.Factory` take a factory of trackers instead of a
+    tracker instance ([#4814](https://github.com/google/ExoPlayer/issues/4814)).
 * DASH:
   * Support `messageData` attribute for in-manifest event streams.
   * Clip periods to their specified durations

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java

@@ -63,8 +63,8 @@ public final class HlsMediaSource extends BaseMediaSource
     private final HlsDataSourceFactory hlsDataSourceFactory;
 
     private HlsExtractorFactory extractorFactory;
-    private @Nullable HlsPlaylistParserFactory playlistParserFactory;
-    private @Nullable HlsPlaylistTracker playlistTracker;
+    private HlsPlaylistParserFactory playlistParserFactory;
+    private HlsPlaylistTracker.Factory playlistTrackerFactory;
     private CompositeSequenceableLoaderFactory compositeSequenceableLoaderFactory;
     private LoadErrorHandlingPolicy loadErrorHandlingPolicy;
     private boolean allowChunklessPreparation;
@@ -90,6 +90,8 @@ public final class HlsMediaSource extends BaseMediaSource
      */
     public Factory(HlsDataSourceFactory hlsDataSourceFactory) {
       this.hlsDataSourceFactory = Assertions.checkNotNull(hlsDataSourceFactory);
+      playlistParserFactory = new DefaultHlsPlaylistParserFactory();
+      playlistTrackerFactory = DefaultHlsPlaylistTracker.FACTORY;
       extractorFactory = HlsExtractorFactory.DEFAULT;
       loadErrorHandlingPolicy = new DefaultLoadErrorHandlingPolicy();
       compositeSequenceableLoaderFactory = new DefaultCompositeSequenceableLoaderFactory();
@@ -131,9 +133,6 @@ public final class HlsMediaSource extends BaseMediaSource
      *
      * <p>Calling this method overrides any calls to {@link #setMinLoadableRetryCount(int)}.
      *
-     * <p>If {@link #setPlaylistTracker} is not called on this builder, {@code
-     * loadErrorHandlingPolicy} is used for creating the used {@link DefaultHlsPlaylistTracker}.
-     *
      * @param loadErrorHandlingPolicy A {@link LoadErrorHandlingPolicy}.
      * @return This factory, for convenience.
      * @throws IllegalStateException If one of the {@code create} methods has already been called.
@@ -168,35 +167,27 @@ public final class HlsMediaSource extends BaseMediaSource
      * Sets the factory from which playlist parsers will be obtained. The default value is created
      * by calling {@link DefaultHlsPlaylistParserFactory#DefaultHlsPlaylistParserFactory()}.
      *
-     * <p>Must not be called after calling {@link #setPlaylistTracker} on the same builder.
-     *
      * @param playlistParserFactory An {@link HlsPlaylistParserFactory}.
      * @return This factory, for convenience.
      * @throws IllegalStateException If one of the {@code create} methods has already been called.
      */
     public Factory setPlaylistParserFactory(HlsPlaylistParserFactory playlistParserFactory) {
       Assertions.checkState(!isCreateCalled);
-      Assertions.checkState(playlistTracker == null, "A playlist tracker has already been set.");
       this.playlistParserFactory = Assertions.checkNotNull(playlistParserFactory);
       return this;
     }
 
     /**
-     * Sets the HLS playlist tracker. The default is an instance of {@link
-     * DefaultHlsPlaylistTracker}. Playlist trackers must not be shared by {@link HlsMediaSource}
-     * instances.
+     * Sets the {@link HlsPlaylistTracker} factory. The default value is {@link
+     * DefaultHlsPlaylistTracker#FACTORY}.
      *
-     * <p>Must not be called after calling {@link #setPlaylistParserFactory} on the same builder.
-     *
-     * @param playlistTracker A tracker for HLS playlists.
+     * @param playlistTrackerFactory A factory for {@link HlsPlaylistTracker} instances.
      * @return This factory, for convenience.
      * @throws IllegalStateException If one of the {@code create} methods has already been called.
      */
-    public Factory setPlaylistTracker(HlsPlaylistTracker playlistTracker) {
+    public Factory setPlaylistTrackerFactory(HlsPlaylistTracker.Factory playlistTrackerFactory) {
       Assertions.checkState(!isCreateCalled);
-      Assertions.checkState(
-          playlistParserFactory == null, "A playlist parser factory has already been set.");
-      this.playlistTracker = Assertions.checkNotNull(playlistTracker);
+      this.playlistTrackerFactory = Assertions.checkNotNull(playlistTrackerFactory);
       return this;
     }
 
@@ -241,26 +232,14 @@ public final class HlsMediaSource extends BaseMediaSource
     @Override
     public HlsMediaSource createMediaSource(Uri playlistUri) {
       isCreateCalled = true;
-      if (playlistTracker == null) {
-        if (playlistParserFactory == null) {
-          playlistTracker =
-              new DefaultHlsPlaylistTracker(
-                  hlsDataSourceFactory,
-                  loadErrorHandlingPolicy,
-                  new DefaultHlsPlaylistParserFactory());
-        } else {
-          playlistTracker =
-              new DefaultHlsPlaylistTracker(
-                  hlsDataSourceFactory, loadErrorHandlingPolicy, playlistParserFactory);
-        }
-      }
       return new HlsMediaSource(
           playlistUri,
           hlsDataSourceFactory,
           extractorFactory,
           compositeSequenceableLoaderFactory,
           loadErrorHandlingPolicy,
-          playlistTracker,
+          playlistTrackerFactory.createTracker(
+              hlsDataSourceFactory, loadErrorHandlingPolicy, playlistParserFactory),
           allowChunklessPreparation,
           tag);
     }

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/DefaultHlsPlaylistTracker.java

@@ -41,6 +41,9 @@ import java.util.List;
 public final class DefaultHlsPlaylistTracker
     implements HlsPlaylistTracker, Loader.Callback<ParsingLoadable<HlsPlaylist>> {
 
+  /** Factory for {@link DefaultHlsPlaylistTracker} instances. */
+  public static final Factory FACTORY = DefaultHlsPlaylistTracker::new;
+
   /**
    * Coefficient applied on the target duration of a playlist to determine the amount of time after
    * which an unchanging playlist is considered stuck.

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistTracker.java

@@ -19,7 +19,9 @@ import android.net.Uri;
 import android.support.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.source.MediaSourceEventListener.EventDispatcher;
+import com.google.android.exoplayer2.source.hls.HlsDataSourceFactory;
 import com.google.android.exoplayer2.source.hls.playlist.HlsMasterPlaylist.HlsUrl;
+import com.google.android.exoplayer2.upstream.LoadErrorHandlingPolicy;
 import java.io.IOException;
 
 /**
@@ -36,6 +38,22 @@ import java.io.IOException;
  */
 public interface HlsPlaylistTracker {
 
+  /** Factory for {@link HlsPlaylistTracker} instances. */
+  interface Factory {
+
+    /**
+     * Creates a new tracker instance.
+     *
+     * @param dataSourceFactory The {@link HlsDataSourceFactory} to use for playlist loading.
+     * @param loadErrorHandlingPolicy The {@link LoadErrorHandlingPolicy} for playlist load errors.
+     * @param playlistParserFactory The {@link HlsPlaylistParserFactory} for playlist parsing.
+     */
+    HlsPlaylistTracker createTracker(
+        HlsDataSourceFactory dataSourceFactory,
+        LoadErrorHandlingPolicy loadErrorHandlingPolicy,
+        HlsPlaylistParserFactory playlistParserFactory);
+  }
+
   /** Listener for primary playlist changes. */
   interface PrimaryPlaylistListener {