Move Player.Listener impl, remove @VisibleForTesting isInitialized. (#6922)

Similar to https://github.com/flutter/packages/pull/6908, as part of https://github.com/flutter/flutter/issues/148417.

I'm working on re-landing https://github.com/flutter/packages/pull/6456, this time without using the `ActivityAware` interface (see https://github.com/flutter/flutter/issues/148417). As part of that work, I'll need to better control the `ExoPlayer` lifecycle and save/restore internal state.

In this PR, I've removed the concept of the class being "initialized" or not - the only thing "initialized" means is "for a given instance of `ExoPlayer`, has received the `'initialized'` event. As a result I removed the quasi-public API that was used for testing only and replaced it with observing what the real production instance does (`Player.STATE_READY`).

After this PR, I'll likely do one more pass around the constructors - the constructor that takes an `ExoPlayer` that is marked `@VisibleForTesting` _also_ doesn't make sense once we'll support suspending/resuming video players, so it will need to get reworked (probably into taking a factory method).

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

@@ -0,0 +1,101 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package io.flutter.plugins.videoplayer;
+
+import androidx.annotation.NonNull;
+import androidx.media3.common.PlaybackException;
+import androidx.media3.common.Player;
+import androidx.media3.common.VideoSize;
+import androidx.media3.exoplayer.ExoPlayer;
+
+final class ExoPlayerEventListener implements Player.Listener {
+  private final ExoPlayer exoPlayer;
+  private final VideoPlayerCallbacks events;
+  private boolean isBuffering = false;
+  private boolean isInitialized = false;
+
+  ExoPlayerEventListener(ExoPlayer exoPlayer, VideoPlayerCallbacks events) {
+    this.exoPlayer = exoPlayer;
+    this.events = events;
+  }
+
+  private void setBuffering(boolean buffering) {
+    if (isBuffering == buffering) {
+      return;
+    }
+    isBuffering = buffering;
+    if (buffering) {
+      events.onBufferingStart();
+    } else {
+      events.onBufferingEnd();
+    }
+  }
+
+  @SuppressWarnings("SuspiciousNameCombination")
+  private void sendInitialized() {
+    if (isInitialized) {
+      return;
+    }
+    isInitialized = true;
+    VideoSize videoSize = exoPlayer.getVideoSize();
+    int rotationCorrection = 0;
+    int width = videoSize.width;
+    int height = videoSize.height;
+    if (width != 0 && height != 0) {
+      int rotationDegrees = videoSize.unappliedRotationDegrees;
+      // Switch the width/height if video was taken in portrait mode
+      if (rotationDegrees == 90 || rotationDegrees == 270) {
+        width = videoSize.height;
+        height = videoSize.width;
+      }
+      // Rotating the video with ExoPlayer does not seem to be possible with a Surface,
+      // so inform the Flutter code that the widget needs to be rotated to prevent
+      // upside-down playback for videos with rotationDegrees of 180 (other orientations work
+      // correctly without correction).
+      if (rotationDegrees == 180) {
+        rotationCorrection = rotationDegrees;
+      }
+    }
+    events.onInitialized(width, height, exoPlayer.getDuration(), rotationCorrection);
+  }
+
+  @Override
+  public void onPlaybackStateChanged(final int playbackState) {
+    switch (playbackState) {
+      case Player.STATE_BUFFERING:
+        setBuffering(true);
+        events.onBufferingUpdate(exoPlayer.getBufferedPosition());
+        break;
+      case Player.STATE_READY:
+        sendInitialized();
+        break;
+      case Player.STATE_ENDED:
+        events.onCompleted();
+        break;
+      case Player.STATE_IDLE:
+        break;
+    }
+    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
+      exoPlayer.seekToDefaultPosition();
+      exoPlayer.prepare();
+    } else {
+      events.onError("VideoError", "Video player had error " + error, null);
+    }
+  }
+
+  @Override
+  public void onIsPlayingChanged(boolean isPlaying) {
+    events.onIsPlayingStateUpdate(isPlaying);
+  }
+}

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

@@ -17,11 +17,7 @@ import androidx.media3.common.AudioAttributes;
 import androidx.media3.common.C;
 import androidx.media3.common.MediaItem;
 import androidx.media3.common.MimeTypes;
-import androidx.media3.common.PlaybackException;
 import androidx.media3.common.PlaybackParameters;
-import androidx.media3.common.Player;
-import androidx.media3.common.Player.Listener;
-import androidx.media3.common.VideoSize;
 import androidx.media3.common.util.UnstableApi;
 import androidx.media3.datasource.DataSource;
 import androidx.media3.datasource.DefaultDataSource;
@@ -47,8 +43,6 @@ final class VideoPlayer {
 
   private static final String USER_AGENT = "User-Agent";
 
-  @VisibleForTesting boolean isInitialized = false;
-
   private final VideoPlayerOptions options;
 
   private final DefaultHttpDataSource.Factory httpDataSourceFactory;
@@ -116,61 +110,7 @@ final class VideoPlayer {
     surface = new Surface(textureEntry.surfaceTexture());
     exoPlayer.setVideoSurface(surface);
     setAudioAttributes(exoPlayer, options.mixWithOthers);
-
-    // Avoids synthetic accessor.
-    VideoPlayerCallbacks events = this.videoPlayerEvents;
-
-    exoPlayer.addListener(
-        new Listener() {
-          private boolean isBuffering = false;
-
-          public void setBuffering(boolean buffering) {
-            if (isBuffering == buffering) {
-              return;
-            }
-            isBuffering = buffering;
-            if (buffering) {
-              events.onBufferingStart();
-            } else {
-              events.onBufferingEnd();
-            }
-          }
-
-          @Override
-          public void onPlaybackStateChanged(final int playbackState) {
-            if (playbackState == Player.STATE_BUFFERING) {
-              setBuffering(true);
-              sendBufferingUpdate();
-            } else if (playbackState == Player.STATE_READY) {
-              if (!isInitialized) {
-                isInitialized = true;
-                sendInitialized();
-              }
-            } else if (playbackState == Player.STATE_ENDED) {
-              events.onCompleted();
-            }
-            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
-              exoPlayer.seekToDefaultPosition();
-              exoPlayer.prepare();
-            } else {
-              events.onError("VideoError", "Video player had error " + error, null);
-            }
-          }
-
-          @Override
-          public void onIsPlayingChanged(boolean isPlaying) {
-            events.onIsPlayingStateUpdate(isPlaying);
-          }
-        });
+    exoPlayer.addListener(new ExoPlayerEventListener(exoPlayer, videoPlayerEvents));
   }
 
   void sendBufferingUpdate() {
@@ -216,38 +156,7 @@ final class VideoPlayer {
     return exoPlayer.getCurrentPosition();
   }
 
-  @SuppressWarnings("SuspiciousNameCombination")
-  @VisibleForTesting
-  void sendInitialized() {
-    if (!isInitialized) {
-      return;
-    }
-    VideoSize videoSize = exoPlayer.getVideoSize();
-    int rotationCorrection = 0;
-    int width = videoSize.width;
-    int height = videoSize.height;
-    if (width != 0 && height != 0) {
-      int rotationDegrees = videoSize.unappliedRotationDegrees;
-      // Switch the width/height if video was taken in portrait mode
-      if (rotationDegrees == 90 || rotationDegrees == 270) {
-        width = videoSize.height;
-        height = videoSize.width;
-      }
-      // Rotating the video with ExoPlayer does not seem to be possible with a Surface,
-      // so inform the Flutter code that the widget needs to be rotated to prevent
-      // upside-down playback for videos with rotationDegrees of 180 (other orientations work
-      // correctly without correction).
-      if (rotationDegrees == 180) {
-        rotationCorrection = rotationDegrees;
-      }
-    }
-    videoPlayerEvents.onInitialized(width, height, exoPlayer.getDuration(), rotationCorrection);
-  }
-
   void dispose() {
-    if (isInitialized) {
-      exoPlayer.stop();
-    }
     textureEntry.release();
     if (surface != null) {
       surface.release();

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

@@ -8,8 +8,10 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import io.flutter.plugin.common.EventChannel;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 final class VideoPlayerEventCallbacks implements VideoPlayerCallbacks {
@@ -66,7 +68,10 @@ final class VideoPlayerEventCallbacks implements VideoPlayerCallbacks {
   public void onBufferingUpdate(long bufferedPosition) {
     // iOS supports a list of buffered ranges, so we send as a list with a single range.
     Map<String, Object> event = new HashMap<>();
-    event.put("values", Collections.singletonList(bufferedPosition));
+    event.put("event", "bufferingUpdate");
+
+    List<? extends Number> range = Arrays.asList(0, bufferedPosition);
+    event.put("values", Collections.singletonList(range));
     eventSink.success(event);
   }
 

packages/video_player/video_player_android/android/src/test/java/io/flutter/plugins/videoplayer/VideoPlayerTest.java

@@ -5,6 +5,7 @@
 package io.flutter.plugins.videoplayer;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyBoolean;
 import static org.mockito.Mockito.*;
@@ -20,10 +21,13 @@ import androidx.media3.common.VideoSize;
 import androidx.media3.datasource.DefaultHttpDataSource;
 import androidx.media3.exoplayer.ExoPlayer;
 import io.flutter.view.TextureRegistry;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -130,22 +134,59 @@ public class VideoPlayerTest {
     verify(httpDataSourceFactorySpy).setDefaultRequestProperties(httpHeaders);
   }
 
+  private Player.Listener initVideoPlayerAndGetListener() {
+    ArgumentCaptor<Player.Listener> listenerCaptor = ArgumentCaptor.forClass(Player.Listener.class);
+    doNothing().when(fakeExoPlayer).addListener(listenerCaptor.capture());
+
+    // Create a video player that will invoke fakeEventSink as a result of Player.Listener calls.
+    new VideoPlayer(
+        fakeExoPlayer,
+        VideoPlayerEventCallbacks.withSink(fakeEventSink),
+        fakeSurfaceTextureEntry,
+        fakeVideoPlayerOptions,
+        httpDataSourceFactorySpy);
+
+    return Objects.requireNonNull(listenerCaptor.getValue());
+  }
+
+  @Test
+  public void onPlaybackStateBufferingSendBufferedPositionUpdate() {
+    Player.Listener listener = initVideoPlayerAndGetListener();
+    when(fakeExoPlayer.getBufferedPosition()).thenReturn(10L);
+
+    // Send Player.STATE_BUFFERING to trigger the "bufferingUpdate" event.
+    listener.onPlaybackStateChanged(Player.STATE_BUFFERING);
+
+    verify(fakeEventSink, atLeast(1)).success(eventCaptor.capture());
+    List<HashMap<String, Object>> events = eventCaptor.getAllValues();
+
+    Map<String, Object> expected = new HashMap<>();
+    expected.put("event", "bufferingUpdate");
+
+    List<? extends Number> range = Arrays.asList(0, 10L);
+    expected.put("values", Collections.singletonList(range));
+
+    // We received potentially multiple events, find the one that is a "bufferingUpdate".
+    for (Map<String, Object> event : events) {
+      if (event.get("event") == "bufferingUpdate") {
+        assertEquals(expected, event);
+        return;
+      }
+    }
+
+    fail("No 'bufferingUpdate' event found: " + events);
+  }
+
   @Test
   public void sendInitializedSendsExpectedEvent_90RotationDegrees() {
-    VideoPlayer videoPlayer =
-        new VideoPlayer(
-            fakeExoPlayer,
-            VideoPlayerEventCallbacks.withSink(fakeEventSink),
-            fakeSurfaceTextureEntry,
-            fakeVideoPlayerOptions,
-            httpDataSourceFactorySpy);
+    Player.Listener listener = initVideoPlayerAndGetListener();
     VideoSize testVideoSize = new VideoSize(100, 200, 90, 1f);
 
     when(fakeExoPlayer.getVideoSize()).thenReturn(testVideoSize);
     when(fakeExoPlayer.getDuration()).thenReturn(10L);
 
-    videoPlayer.isInitialized = true;
-    videoPlayer.sendInitialized();
+    // Send Player.STATE_READY to trigger the "initialized" event.
+    listener.onPlaybackStateChanged(Player.STATE_READY);
 
     verify(fakeEventSink).success(eventCaptor.capture());
     HashMap<String, Object> actual = eventCaptor.getValue();
@@ -161,20 +202,14 @@ public class VideoPlayerTest {
 
   @Test
   public void sendInitializedSendsExpectedEvent_270RotationDegrees() {
-    VideoPlayer videoPlayer =
-        new VideoPlayer(
-            fakeExoPlayer,
-            VideoPlayerEventCallbacks.withSink(fakeEventSink),
-            fakeSurfaceTextureEntry,
-            fakeVideoPlayerOptions,
-            httpDataSourceFactorySpy);
+    Player.Listener listener = initVideoPlayerAndGetListener();
     VideoSize testVideoSize = new VideoSize(100, 200, 270, 1f);
 
     when(fakeExoPlayer.getVideoSize()).thenReturn(testVideoSize);
     when(fakeExoPlayer.getDuration()).thenReturn(10L);
 
-    videoPlayer.isInitialized = true;
-    videoPlayer.sendInitialized();
+    // Send Player.STATE_READY to trigger the "initialized" event.
+    listener.onPlaybackStateChanged(Player.STATE_READY);
 
     verify(fakeEventSink).success(eventCaptor.capture());
     HashMap<String, Object> actual = eventCaptor.getValue();
@@ -190,20 +225,14 @@ public class VideoPlayerTest {
 
   @Test
   public void sendInitializedSendsExpectedEvent_0RotationDegrees() {
-    VideoPlayer videoPlayer =
-        new VideoPlayer(
-            fakeExoPlayer,
-            VideoPlayerEventCallbacks.withSink(fakeEventSink),
-            fakeSurfaceTextureEntry,
-            fakeVideoPlayerOptions,
-            httpDataSourceFactorySpy);
+    Player.Listener listener = initVideoPlayerAndGetListener();
     VideoSize testVideoSize = new VideoSize(100, 200, 0, 1f);
 
     when(fakeExoPlayer.getVideoSize()).thenReturn(testVideoSize);
     when(fakeExoPlayer.getDuration()).thenReturn(10L);
 
-    videoPlayer.isInitialized = true;
-    videoPlayer.sendInitialized();
+    // Send Player.STATE_READY to trigger the "initialized" event.
+    listener.onPlaybackStateChanged(Player.STATE_READY);
 
     verify(fakeEventSink).success(eventCaptor.capture());
     HashMap<String, Object> actual = eventCaptor.getValue();
@@ -219,20 +248,14 @@ public class VideoPlayerTest {
 
   @Test
   public void sendInitializedSendsExpectedEvent_180RotationDegrees() {
-    VideoPlayer videoPlayer =
-        new VideoPlayer(
-            fakeExoPlayer,
-            VideoPlayerEventCallbacks.withSink(fakeEventSink),
-            fakeSurfaceTextureEntry,
-            fakeVideoPlayerOptions,
-            httpDataSourceFactorySpy);
+    Player.Listener listener = initVideoPlayerAndGetListener();
     VideoSize testVideoSize = new VideoSize(100, 200, 180, 1f);
 
     when(fakeExoPlayer.getVideoSize()).thenReturn(testVideoSize);
     when(fakeExoPlayer.getDuration()).thenReturn(10L);
 
-    videoPlayer.isInitialized = true;
-    videoPlayer.sendInitialized();
+    // Send Player.STATE_READY to trigger the "initialized" event.
+    listener.onPlaybackStateChanged(Player.STATE_READY);
 
     verify(fakeEventSink).success(eventCaptor.capture());
     HashMap<String, Object> actual = eventCaptor.getValue();