Add pre-caching functionality in DefaultPreloadManager

Apps now can return `DefaultPreloadManager.PreloadStatus.specifiedRangeCached(startPositionMs, durationMs)` or `DefaultPreloadManager.PreloadStatus.specifiedRangeCached(durationMs)` via `TargetPreloadStatusControl.getTargetPreloadStatus(T rankingData)` to indicate that a media item needs to be pre-cached.

PiperOrigin-RevId: 785912919

Author: tianyif

RELEASENOTES.md

@@ -23,6 +23,13 @@
         to call this method on the same thread as ExoPlayer's playback thread or
         use a different instance than the one used for playback
         ([#1191](https://github.com/androidx/media/issues/1191)).
+    *   Add pre-caching functionality in `DefaultPreloadManager`. Apps now can
+        return
+        `DefaultPreloadManager.PreloadStatus.specifiedRangeCached(startPositionMs,
+        durationMs)` or
+        `DefaultPreloadManager.PreloadStatus.specifiedRangeCached(durationMs)`
+        via `TargetPreloadStatusControl.getTargetPreloadStatus(T rankingData)`
+        to indicate that a media item needs to be pre-cached.
 *   Transformer:
 *   Track Selection:
     *   Add `TrackSelectionParameters.selectTextByDefault` to prefer the

demos/shortform/src/main/java/androidx/media3/demo/shortform/viewpager/ViewPagerMediaAdapter.kt

@@ -174,13 +174,13 @@ class ViewPagerMediaAdapter(
   inner class DefaultTargetPreloadStatusControl(var currentPlayingIndex: Int = C.INDEX_UNSET) :
     TargetPreloadStatusControl<Int, DefaultPreloadManager.PreloadStatus> {
 
-    override fun getTargetPreloadStatus(rankingData: Int): DefaultPreloadManager.PreloadStatus? {
+    override fun getTargetPreloadStatus(rankingData: Int): DefaultPreloadManager.PreloadStatus {
       if (abs(rankingData - currentPlayingIndex) == 2) {
         return DefaultPreloadManager.PreloadStatus.specifiedRangeLoaded(/* durationMs= */ 500L)
       } else if (abs(rankingData - currentPlayingIndex) == 1) {
         return DefaultPreloadManager.PreloadStatus.specifiedRangeLoaded(/* durationMs= */ 1000L)
       }
-      return null
+      return DefaultPreloadManager.PreloadStatus.PRELOAD_STATUS_NOT_PRELOADED
     }
   }
 }

libraries/exoplayer/src/androidTest/java/androidx/media3/exoplayer/source/preload/DefaultPreloadManagerBinderStressTest.java

@@ -52,7 +52,9 @@ public void binderStressTest() throws Exception {
         /* systemUnderTest= */ () -> {
           DefaultPreloadManager.Builder builder =
               new DefaultPreloadManager.Builder(
-                      context, rankingData -> DefaultPreloadManager.PreloadStatus.SOURCE_PREPARED)
+                      context,
+                      rankingData ->
+                          DefaultPreloadManager.PreloadStatus.PRELOAD_STATUS_SOURCE_PREPARED)
                   .setBandwidthMeter(new DefaultBandwidthMeter.Builder(context).build());
           MediaItem mediaItem = MediaItem.fromUri("http://test.test");