Expand MediaItems in session demo instead of just replacing them

When MediaItems are added from the controller, we currently completely
replace the item with the one from our database, overriding any
potential additional information the controller may have set.

Also forward the onAddMediaItems/onSetMediaItems callbacks to common
helper methods instead of redirecting them through super methods

#minor-release
Issue: androidx/media#706
PiperOrigin-RevId: 573799351

demos/session/src/main/java/androidx/media3/demo/session/PlayableFolderActivity.kt

@@ -88,7 +88,7 @@ class PlayableFolderActivity : AppCompatActivity() {
       browser.shuffleModeEnabled = true
       browser.prepare()
       browser.play()
-      browser?.sessionActivity?.send()
+      browser.sessionActivity?.send()
     }
 
     findViewById<Button>(R.id.play_button).setOnClickListener {

demos/session_service/src/main/java/androidx/media3/demo/session/DemoMediaLibrarySessionCallback.kt

@@ -25,6 +25,7 @@ import androidx.media3.session.CommandButton
 import androidx.media3.session.LibraryResult
 import androidx.media3.session.MediaLibraryService
 import androidx.media3.session.MediaSession
+import androidx.media3.session.MediaSession.MediaItemsWithStartPosition
 import androidx.media3.session.SessionCommand
 import androidx.media3.session.SessionResult
 import com.google.common.collect.ImmutableList
@@ -32,7 +33,7 @@ import com.google.common.util.concurrent.Futures
 import com.google.common.util.concurrent.ListenableFuture
 
 /** A [MediaLibraryService.MediaLibrarySession.Callback] implementation. */
-open class DemoMediaLibrarySessionCallback(private val context: Context) :
+open class DemoMediaLibrarySessionCallback(context: Context) :
   MediaLibraryService.MediaLibrarySession.Callback {
 
   init {
@@ -155,14 +156,7 @@ open class DemoMediaLibrarySessionCallback(private val context: Context) :
     controller: MediaSession.ControllerInfo,
     mediaItems: List<MediaItem>
   ): ListenableFuture<List<MediaItem>> {
-    val playlist = mutableListOf<MediaItem>()
+    return Futures.immediateFuture(resolveMediaItems(mediaItems))
-    mediaItems.forEach { mediaItem ->
-      when (mediaItem.requestMetadata.searchQuery) {
-        null -> MediaItemTree.getItem(mediaItem.mediaId)?.let { playlist.add(it) }
-        else -> playlist.addAll(MediaItemTree.search(mediaItem.requestMetadata.searchQuery!!))
-      }
-    }
-    return Futures.immediateFuture(playlist)
   }
 
   @OptIn(UnstableApi::class) // MediaSession.MediaItemsWithStartPosition
@@ -172,34 +166,57 @@ open class DemoMediaLibrarySessionCallback(private val context: Context) :
     mediaItems: List<MediaItem>,
     startIndex: Int,
     startPositionMs: Long
-  ): ListenableFuture<MediaSession.MediaItemsWithStartPosition> {
+  ): ListenableFuture<MediaItemsWithStartPosition> {
     if (mediaItems.size == 1) {
       // Try to expand a single item to a playlist.
-      val mediaId = mediaItems.first().mediaId
+      maybeExpandSingleItemToPlaylist(mediaItems.first(), startIndex, startPositionMs)?.also {
-      val mediaItem = MediaItemTree.getItem(mediaId)
+        return Futures.immediateFuture(it)
+      }
+    }
+    return Futures.immediateFuture(
+      MediaItemsWithStartPosition(resolveMediaItems(mediaItems), startIndex, startPositionMs)
+    )
+  }
+
+  private fun resolveMediaItems(mediaItems: List<MediaItem>): List<MediaItem> {
     val playlist = mutableListOf<MediaItem>()
+    mediaItems.forEach { mediaItem ->
+      if (mediaItem.mediaId.isNotEmpty()) {
+        MediaItemTree.expandItem(mediaItem)?.let { playlist.add(it) }
+      } else if (mediaItem.requestMetadata.searchQuery != null) {
+        playlist.addAll(MediaItemTree.search(mediaItem.requestMetadata.searchQuery!!))
+      }
+    }
+    return playlist
+  }
+
+  @OptIn(UnstableApi::class) // MediaSession.MediaItemsWithStartPosition
+  private fun maybeExpandSingleItemToPlaylist(
+    mediaItem: MediaItem,
+    startIndex: Int,
+    startPositionMs: Long
+  ): MediaItemsWithStartPosition? {
+    var playlist = listOf<MediaItem>()
     var indexInPlaylist = startIndex
-      mediaItem?.apply {
+    MediaItemTree.getItem(mediaItem.mediaId)?.apply {
       if (mediaMetadata.isBrowsable == true) {
         // Get children browsable item.
-          playlist.addAll(MediaItemTree.getChildren(mediaId))
+        playlist = MediaItemTree.getChildren(mediaId)
       } else if (requestMetadata.searchQuery == null) {
         // Try to get the parent and its children.
         MediaItemTree.getParentId(mediaId)?.let {
-            playlist.addAll(MediaItemTree.getChildren(it))
+          playlist =
+            MediaItemTree.getChildren(it).map { mediaItem ->
+              if (mediaItem.mediaId == mediaId) MediaItemTree.expandItem(mediaItem)!! else mediaItem
+            }
           indexInPlaylist = MediaItemTree.getIndexInMediaItems(mediaId, playlist)
         }
       }
     }
     if (playlist.isNotEmpty()) {
-        // Return the expanded playlist to be set on the player of the session.
+      return MediaItemsWithStartPosition(playlist, indexInPlaylist, startPositionMs)
-        return Futures.immediateFuture(
-          MediaSession.MediaItemsWithStartPosition(playlist, indexInPlaylist, startPositionMs)
-        )
     }
-    }
+    return null
-    // Let super serve the request if item isn't expanded.
-    return super.onSetMediaItems(mediaSession, browser, mediaItems, startIndex, startPositionMs)
   }
 
   override fun onSearch(

demos/session_service/src/main/java/androidx/media3/demo/session/MediaItemTree.kt

@@ -17,9 +17,11 @@ package androidx.media3.demo.session
 
 import android.content.res.AssetManager
 import android.net.Uri
+import androidx.annotation.OptIn
 import androidx.media3.common.MediaItem
 import androidx.media3.common.MediaItem.SubtitleConfiguration
 import androidx.media3.common.MediaMetadata
+import androidx.media3.common.util.UnstableApi
 import com.google.common.collect.ImmutableList
 import java.io.BufferedReader
 import java.lang.StringBuilder
@@ -275,6 +277,18 @@ object MediaItemTree {
     return treeNodes[id]?.item
   }
 
+  fun expandItem(item: MediaItem): MediaItem? {
+    val treeItem = getItem(item.mediaId) ?: return null
+    @OptIn(UnstableApi::class) // MediaMetadata.populate
+    val metadata = treeItem.mediaMetadata.buildUpon().populate(item.mediaMetadata).build()
+    return item
+      .buildUpon()
+      .setMediaMetadata(metadata)
+      .setSubtitleConfigurations(treeItem.localConfiguration?.subtitleConfigurations ?: listOf())
+      .setUri(treeItem.localConfiguration?.uri)
+      .build()
+  }
+
   /**
    * Returns the media ID of the parent of the given media ID, or null if the media ID wasn't found.
    *
@@ -342,19 +356,6 @@ object MediaItemTree {
     return treeNodes[id]?.getChildren() ?: listOf()
   }
 
-  fun getRandomItem(): MediaItem {
-    var curRoot = getRootItem()
-    while (curRoot.mediaMetadata.isBrowsable == true) {
-      val children = getChildren(curRoot.mediaId)
-      curRoot = children.random()
-    }
-    return curRoot
-  }
-
-  fun getItemFromTitle(title: String): MediaItem? {
-    return titleMap[title]?.item
-  }
-
   private fun normalizeSearchText(text: CharSequence?): String {
     if (text.isNullOrEmpty() || text.trim().length == 1) {
       return ""