Allow simplified custom adaptive track selection factories.

Custom factories currently need to copy most of the code in the
AdaptiveTrackSelection.Factory to make use of the same functionality.
Simplify this by allowing to overwrite the factory.

PiperOrigin-RevId: 240773271

library/core/src/main/java/com/google/android/exoplayer2/trackselection/AdaptiveTrackSelection.java

@@ -36,10 +36,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
  */
 public class AdaptiveTrackSelection extends BaseTrackSelection {
 
-  /**
-   * Factory for {@link AdaptiveTrackSelection} instances.
-   */
-  public static final class Factory implements TrackSelection.Factory {
+  /** Factory for {@link AdaptiveTrackSelection} instances. */
+  public static class Factory implements TrackSelection.Factory {
 
     private final @Nullable BandwidthMeter bandwidthMeter;
     private final int minDurationForQualityIncreaseMs;
@@ -215,7 +213,8 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
      *
      * @param trackBitrateEstimator A {@link TrackBitrateEstimator}.
      */
-    public void experimental_setTrackBitrateEstimator(TrackBitrateEstimator trackBitrateEstimator) {
+    public final void experimental_setTrackBitrateEstimator(
+        TrackBitrateEstimator trackBitrateEstimator) {
       this.trackBitrateEstimator = trackBitrateEstimator;
     }
 
@@ -224,13 +223,16 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
      *
      * <p>This method is experimental, and will be renamed or removed in a future release.
      */
-    public void experimental_enableBlockFixedTrackSelectionBandwidth() {
+    public final void experimental_enableBlockFixedTrackSelectionBandwidth() {
       this.blockFixedTrackSelectionBandwidth = true;
     }
 
     @Override
-    public @NullableType TrackSelection[] createTrackSelections(
+    public final @NullableType TrackSelection[] createTrackSelections(
         @NullableType Definition[] definitions, BandwidthMeter bandwidthMeter) {
+      if (this.bandwidthMeter != null) {
+        bandwidthMeter = this.bandwidthMeter;
+      }
       TrackSelection[] selections = new TrackSelection[definitions.length];
       List<AdaptiveTrackSelection> adaptiveSelections = new ArrayList<>();
       int totalFixedBandwidth = 0;
@@ -242,6 +244,7 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
         if (definition.tracks.length > 1) {
           AdaptiveTrackSelection adaptiveSelection =
               createAdaptiveTrackSelection(definition.group, bandwidthMeter, definition.tracks);
+          adaptiveSelection.experimental_setTrackBitrateEstimator(trackBitrateEstimator);
           adaptiveSelections.add(adaptiveSelection);
           selections[i] = adaptiveSelection;
         } else {
@@ -279,24 +282,26 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
       return selections;
     }
 
-    private AdaptiveTrackSelection createAdaptiveTrackSelection(
+    /**
+     * Creates a single adaptive selection for the given group, bandwidth meter and tracks.
+     *
+     * @param group The {@link TrackGroup}.
+     * @param bandwidthMeter A {@link BandwidthMeter} which can be used to select tracks.
+     * @param tracks The indices of the selected tracks in the track group.
+     * @return An {@link AdaptiveTrackSelection} for the specified tracks.
+     */
+    protected AdaptiveTrackSelection createAdaptiveTrackSelection(
         TrackGroup group, BandwidthMeter bandwidthMeter, int[] tracks) {
-      if (this.bandwidthMeter != null) {
-        bandwidthMeter = this.bandwidthMeter;
-      }
-      AdaptiveTrackSelection adaptiveTrackSelection =
-          new AdaptiveTrackSelection(
-              group,
-              tracks,
-              new DefaultBandwidthProvider(bandwidthMeter, bandwidthFraction),
-              minDurationForQualityIncreaseMs,
-              maxDurationForQualityDecreaseMs,
-              minDurationToRetainAfterDiscardMs,
-              bufferedFractionToLiveEdgeForQualityIncrease,
-              minTimeBetweenBufferReevaluationMs,
-              clock);
-      adaptiveTrackSelection.experimental_setTrackBitrateEstimator(trackBitrateEstimator);
-      return adaptiveTrackSelection;
+      return new AdaptiveTrackSelection(
+          group,
+          tracks,
+          new DefaultBandwidthProvider(bandwidthMeter, bandwidthFraction),
+          minDurationForQualityIncreaseMs,
+          maxDurationForQualityDecreaseMs,
+          minDurationToRetainAfterDiscardMs,
+          bufferedFractionToLiveEdgeForQualityIncrease,
+          minTimeBetweenBufferReevaluationMs,
+          clock);
     }
   }