Add TrackSelector.release()

The TrackSelector is released when the player is released. The
TrackSelector can be reused if TrackSelector.init() is called again.

PiperOrigin-RevId: 446439717

library/core/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java

@@ -969,6 +969,7 @@ import java.util.concurrent.TimeoutException;
     playbackInfo.bufferedPositionUs = playbackInfo.positionUs;
     playbackInfo.totalBufferedDurationUs = 0;
     analyticsCollector.release();
+    trackSelector.release();
     removeSurfaceCallbacks();
     if (ownedSurface != null) {
       ownedSurface.release();

library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadHelper.java

@@ -513,6 +513,7 @@ public final class DownloadHelper {
     if (mediaPreparer != null) {
       mediaPreparer.release();
     }
+    trackSelector.release();
   }
 
   /**

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

@@ -15,9 +15,12 @@
  */
 package com.google.android.exoplayer2.trackselection;
 
+import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
+
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.ExoPlayer;
+import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Renderer;
 import com.google.android.exoplayer2.RendererCapabilities;
 import com.google.android.exoplayer2.RendererConfiguration;
@@ -25,7 +28,6 @@ import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.source.MediaSource.MediaPeriodId;
 import com.google.android.exoplayer2.source.TrackGroupArray;
 import com.google.android.exoplayer2.upstream.BandwidthMeter;
-import com.google.android.exoplayer2.util.Assertions;
 
 /**
  * The component of an {@link ExoPlayer} responsible for selecting tracks to be consumed by each of
@@ -63,6 +65,8 @@ import com.google.android.exoplayer2.util.Assertions;
  *       track selection for the currently playing period differs from the one that was invalidated.
  *       Implementing subclasses can trigger invalidation by calling {@link #invalidate()}, which
  *       will call {@link InvalidationListener#onTrackSelectionsInvalidated()}.
+ *   <li>When the player is {@linkplain Player#release() released}, it will release the track
+ *       selector by calling {@link #release()}.
  * </ul>
  *
  * <h2>Renderer configuration</h2>
@@ -111,6 +115,15 @@ public abstract class TrackSelector {
   }
 
   /**
+   * Called by the player to release the selector. The selector cannot be used until {@link
+   * #init(InvalidationListener, BandwidthMeter)} is called again.
+   */
+  public final void release() {
+    this.listener = null;
+    this.bandwidthMeter = null;
+  }
+
+  /**
    * Called by the player to perform a track selection.
    *
    * @param rendererCapabilities The {@link RendererCapabilities} of the renderers for which tracks
@@ -174,9 +187,10 @@ public abstract class TrackSelector {
 
   /**
    * Returns a bandwidth meter which can be used by track selections to select tracks. Must only be
-   * called after {@link #init(InvalidationListener, BandwidthMeter)} has been called.
+   * called when the track selector is {@linkplain #init(InvalidationListener, BandwidthMeter)
+   * initialized}.
    */
   protected final BandwidthMeter getBandwidthMeter() {
-    return Assertions.checkNotNull(bandwidthMeter);
+    return checkStateNotNull(bandwidthMeter);
   }
 }

library/core/src/test/java/com/google/android/exoplayer2/trackselection/DefaultTrackSelectorTest.java

@@ -61,6 +61,7 @@ import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import java.util.HashMap;
 import java.util.Map;
+import org.junit.After;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -145,6 +146,11 @@ public final class DefaultTrackSelectorTest {
     trackSelector.init(invalidationListener, bandwidthMeter);
   }
 
+  @After
+  public void tearDown() {
+    trackSelector.release();
+  }
+
   @Test
   public void parameters_buildUponThenBuild_isEqual() {
     Parameters parameters = buildParametersForEqualsTest();

library/core/src/test/java/com/google/android/exoplayer2/trackselection/TrackSelectorTest.java

@@ -16,7 +16,7 @@
 package com.google.android.exoplayer2.trackselection;
 
 import static com.google.common.truth.Truth.assertThat;
-import static org.junit.Assert.fail;
+import static org.junit.Assert.assertThrows;
 
 import androidx.annotation.Nullable;
 import androidx.test.ext.junit.runners.AndroidJUnit4;
@@ -59,12 +59,7 @@ public class TrackSelectorTest {
 
   @Test
   public void getBandwidthMeter_beforeInitialization_throwsException() {
-    try {
-      trackSelector.getBandwidthMeter();
-      fail();
-    } catch (Exception e) {
-      // Expected.
-    }
+    assertThrows(IllegalStateException.class, () -> trackSelector.getBandwidthMeter());
   }
 
   @Test
@@ -73,6 +68,30 @@ public class TrackSelectorTest {
     BandwidthMeter bandwidthMeter = Mockito.mock(BandwidthMeter.class);
     trackSelector.init(invalidationListener, bandwidthMeter);
 
-    assertThat(trackSelector.getBandwidthMeter()).isEqualTo(bandwidthMeter);
+    assertThat(trackSelector.getBandwidthMeter()).isSameInstanceAs(bandwidthMeter);
+  }
+
+  @Test
+  public void getBandwidthMeter_afterRelease_throwsException() {
+    InvalidationListener invalidationListener = Mockito.mock(InvalidationListener.class);
+    BandwidthMeter bandwidthMeter = Mockito.mock(BandwidthMeter.class);
+    trackSelector.init(invalidationListener, bandwidthMeter);
+
+    trackSelector.release();
+
+    assertThrows(IllegalStateException.class, () -> trackSelector.getBandwidthMeter());
+  }
+
+  @Test
+  public void initialize_afterRelease() {
+    InvalidationListener invalidationListener = Mockito.mock(InvalidationListener.class);
+    BandwidthMeter bandwidthMeter = Mockito.mock(BandwidthMeter.class);
+    trackSelector.init(invalidationListener, bandwidthMeter);
+
+    trackSelector.release();
+    BandwidthMeter anotherBandwidthMeter = Mockito.mock(BandwidthMeter.class);
+    trackSelector.init(invalidationListener, anotherBandwidthMeter);
+
+    assertThat(trackSelector.getBandwidthMeter()).isSameInstanceAs(anotherBandwidthMeter);
   }
 }