feat(android): add audio track selection for ExoPlayer

- Implemented getAudioTracks() and selectAudioTrack() methods for Android video player using ExoPlayer
- Removed Kotlin dependencies and switched back to pure Java implementation
- Updated event listener to handle buffering states more accurately with start/end events
- Simplified playback state handling by removing unnecessary state enum

Author: nateshmbhat

packages/video_player/video_player_android/CHANGELOG.md

@@ -1,9 +1,6 @@
-## 2.8.17
+## 2.9.0
 
-* Moves video event processing logic to Dart, and fixes an issue where buffer
-  range would not be updated for a paused video.
-* Switches to Kotlin for Pigeon-generated code.
-* Adopts type-safe event channels for internal communication.
+* Implements `getAudioTracks()` and `selectAudioTrack()` methods for Android using ExoPlayer.
 
 ## 2.8.16
 

packages/video_player/video_player_android/android/build.gradle

@@ -2,15 +2,13 @@ group = 'io.flutter.plugins.videoplayer'
 version = '1.0-SNAPSHOT'
 
 buildscript {
-    ext.kotlin_version = '2.2.10'
     repositories {
         google()
         mavenCentral()
     }
 
     dependencies {
         classpath 'com.android.tools.build:gradle:8.12.1'
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
 
@@ -22,7 +20,6 @@ rootProject.allprojects {
 }
 
 apply plugin: 'com.android.library'
-apply plugin: 'kotlin-android'
 
 android {
     namespace = "io.flutter.plugins.videoplayer"
@@ -41,13 +38,6 @@ android {
         sourceCompatibility = JavaVersion.VERSION_17
         targetCompatibility = JavaVersion.VERSION_17
     }
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_17.toString()
-    }
-
-    sourceSets {
-        main.java.srcDirs += 'src/main/kotlin'
-    }
 
     dependencies {
         def exoplayer_version = "1.5.1"

packages/video_player/video_player_android/android/src/main/java/io/flutter/plugins/videoplayer/ExoPlayerEventListener.java

@@ -10,6 +10,7 @@
 import androidx.media3.exoplayer.ExoPlayer;
 
 public abstract class ExoPlayerEventListener implements Player.Listener {
+  private boolean isBuffering = false;
   private boolean isInitialized = false;
   protected final ExoPlayer exoPlayer;
   protected final VideoPlayerCallbacks events;
@@ -46,34 +47,47 @@ public ExoPlayerEventListener(
     this.events = events;
   }
 
+  private void setBuffering(boolean buffering) {
+    if (isBuffering == buffering) {
+      return;
+    }
+    isBuffering = buffering;
+    if (buffering) {
+      events.onBufferingStart();
+    } else {
+      events.onBufferingEnd();
+    }
+  }
+
   protected abstract void sendInitialized();
 
   @Override
   public void onPlaybackStateChanged(final int playbackState) {
-    PlatformPlaybackState platformState = PlatformPlaybackState.UNKNOWN;
     switch (playbackState) {
       case Player.STATE_BUFFERING:
-        platformState = PlatformPlaybackState.BUFFERING;
+        setBuffering(true);
+        events.onBufferingUpdate(exoPlayer.getBufferedPosition());
         break;
       case Player.STATE_READY:
-        platformState = PlatformPlaybackState.READY;
         if (!isInitialized) {
           isInitialized = true;
           sendInitialized();
         }
         break;
       case Player.STATE_ENDED:
-        platformState = PlatformPlaybackState.ENDED;
+        events.onCompleted();
         break;
       case Player.STATE_IDLE:
-        platformState = PlatformPlaybackState.IDLE;
         break;
     }
-    events.onPlaybackStateChanged(platformState);
+    if (playbackState != Player.STATE_BUFFERING) {
+      setBuffering(false);
+    }
   }
 
   @Override
   public void onPlayerError(@NonNull final PlaybackException error) {
+    setBuffering(false);
     if (error.errorCode == PlaybackException.ERROR_CODE_BEHIND_LIVE_WINDOW) {
       // See
       // https://exoplayer.dev/live-streaming.html#behindlivewindowexception-and-error_code_behind_live_window