Android ExoPlayer屏幕旋转时自动恢复视频播放问题求助

我太懂这个坑了——用FragmentStatePagerAdapter管理带SimpleExoPlayerView的Fragment时，屏幕旋转不仅会触发Fragment重建，连播放器视图也会被重置，明明存了播放位置却没法自动续播。这核心问题在于Fragment和播放器实例的生命周期没对齐，下面给你一步步拆解修复方案：

1. 用ViewModel托管ExoPlayer，脱离Fragment生命周期 #

Fragment在配置变化（比如旋转）时会被销毁重建，但ViewModel会保留下来。把播放器实例放到ViewModel里，就能避免重建时丢失播放器状态：

编写PlayerViewModel #

class PlayerViewModel : ViewModel() {
    var player: SimpleExoPlayer? = null
    var playbackPosition: Long = 0
    var currentWindow: Int = 0
    var playWhenReady: Boolean = true

    // 初始化播放器，复用已有实例
    fun initializePlayer(context: Context) {
        if (player == null) {
            player = SimpleExoPlayer.Builder(context).build().apply {
                playWhenReady = this@PlayerViewModel.playWhenReady
                seekTo(currentWindow, playbackPosition)
            }
        }
    }

    // 释放播放器，仅在ViewModel销毁时调用
    fun releasePlayer() {
        player?.let {
            // 保存当前状态
            playbackPosition = it.currentPosition
            currentWindow = it.currentWindowIndex
            playWhenReady = it.playWhenReady
            it.release()
            player = null
        }
    }

    override fun onCleared() {
        super.onCleared()
        releasePlayer() // 页面真正销毁时释放资源
    }
}

2. 改造Fragment，绑定ViewModel与播放器视图 #

Fragment只负责视图的创建和绑定，播放器的生命周期交给ViewModel管理：

class VideoFragment : Fragment() {
    private lateinit var playerViewModel: PlayerViewModel
    private var playerView: SimpleExoPlayerView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        playerViewModel = ViewModelProvider(this).get(PlayerViewModel::class.java)
        
        // 从savedInstanceState恢复进程被杀后的状态
        savedInstanceState?.let {
            playerViewModel.playbackPosition = it.getLong("playbackPosition", 0)
            playerViewModel.currentWindow = it.getInt("currentWindow", 0)
            playerViewModel.playWhenReady = it.getBoolean("playWhenReady", true)
        }
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        playerView = view.findViewById(R.id.player_view)
        
        // 初始化并绑定播放器到视图
        playerViewModel.initializePlayer(requireContext())
        playerView?.player = playerViewModel.player
        
        // 设置媒体源（这里从Fragment参数取视频地址，根据你的实际逻辑调整）
        val mediaUrl = arguments?.getString("video_url") ?: ""
        playerViewModel.player?.setMediaItem(MediaItem.fromUri(mediaUrl))
        playerViewModel.player?.prepare()
    }

    override fun onDestroyView() {
        super.onDestroyView()
        // 视图销毁时只解绑播放器，不释放（ViewModel还持有实例）
        playerView?.player = null
        playerView = null
    }

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        // 保存状态到Bundle，应对进程被杀场景
        playerViewModel.player?.let {
            outState.putLong("playbackPosition", it.currentPosition)
            outState.putInt("currentWindow", it.currentWindowIndex)
            outState.putBoolean("playWhenReady", it.playWhenReady)
        }
    }
}

3. 优化PagerAdapter的Fragment管理 #

如果你用的是AndroidX的FragmentStatePagerAdapter，记得传入BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT参数，减少后台Fragment的不必要生命周期触发：

class VideoPagerAdapter(fm: FragmentManager) : FragmentStatePagerAdapter(
    fm,
    BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT
) {
    private val videoList = listOf("video_url_1", "video_url_2", "video_url_3")

    override fun getItem(position: Int): Fragment {
        return VideoFragment().apply {
            arguments = Bundle().apply {
                putString("video_url", videoList[position])
            }
        }
    }

    override fun getCount(): Int = videoList.size
}

4. 可选：切换到ViewPager2（更稳定的方案） #

FragmentStatePagerAdapter已经被标记为Deprecated，官方推荐用ViewPager2 + FragmentStateAdapter，它的Fragment生命周期管理更严谨，配置变化时的行为更可控：

class VideoPagerAdapter(fragment: Fragment) : FragmentStateAdapter(fragment) {
    private val videoList = listOf("video_url_1", "video_url_2", "video_url_3")

    override fun getItemCount(): Int = videoList.size

    override fun createFragment(position: Int): Fragment {
        return VideoFragment().apply {
            arguments = Bundle().apply {
                putString("video_url", videoList[position])
            }
        }
    }
}

关键注意点 #

• 不要在Fragment的onActivityCreated里恢复状态，而是通过ViewModel绑定，因为ViewModel会自动跨越配置变化。
• 务必在ViewModel的onCleared方法里释放播放器，避免内存泄漏。
• onSaveInstanceState仅用于应对进程被杀的场景，日常配置变化的状态由ViewModel保存即可。

内容的提问来源于stack exchange，提问作者M.Ali