import android.content.Context
import androidx.recyclerview.widget.LinearSmoothScroller

class TopLinearSmoothScroller(context: Context?) : LinearSmoothScroller(context) {
    public override fun getVerticalSnapPreference(): Int {
        return SNAP_TO_START
    }

    override fun getHorizontalSnapPreference(): Int {
        return SNAP_TO_START
    }
}

import android.content.Context
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

class TopScrollLinearLayoutManager(context: Context?, orientation: Int, reverseLayout: Boolean) :
    LinearLayoutManager(context, orientation, reverseLayout) {

    override fun smoothScrollToPosition(
        recyclerView: RecyclerView?,
        state: RecyclerView.State?,
        position: Int
    ) {
        val linearSmoothScroller = TopLinearSmoothScroller(recyclerView?.context)
        linearSmoothScroller.targetPosition = position
        startSmoothScroll(linearSmoothScroller)
    }
}

recyclerView.layoutManager = TopScrollLinearLayoutManager(
    this,
    LinearLayoutManager.HORIZONTAL,
    false
)
// ...
recyclerView.smoothScrollToPosition(1)

import android.os.Bundle
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import com.google.android.exoplayer2.ExoPlayer
import com.google.android.exoplayer2.MediaItem
import com.google.android.exoplayer2.PlaybackException
import com.google.android.exoplayer2.Player
import com.google.android.exoplayer2.Player.Listener
import com.google.android.exoplayer2.ui.StyledPlayerView

class ExoPlayerFragment : Fragment() {

    companion object {
        fun newInstance(url: String): ExoPlayerFragment {
            val args = Bundle()
            args.putString(EXO_URI, url)
            val fragment = ExoPlayerFragment()
            fragment.arguments = args
            return fragment
        }

        private const val TAG = "ExoPlayerFragment"
        private const val EXO_URI = "EXO_URI"
    }

    private var videoUri: String? = null
    private var player: ExoPlayer? = null

    private val listener = object : Listener {

        override fun onEvents(player: Player, events: Player.Events) {
            super.onEvents(player, events)
            Log.d(TAG, "onEvents->${events}:")
        }

        override fun onPlaybackStateChanged(playbackState: Int) {
            val stateString: String = when (playbackState) {
                ExoPlayer.STATE_IDLE -> "ExoPlayer.STATE_IDLE"
                ExoPlayer.STATE_BUFFERING -> "ExoPlayer.STATE_BUFFERING"
                ExoPlayer.STATE_READY -> "ExoPlayer.STATE_READY"
                ExoPlayer.STATE_ENDED -> "ExoPlayer.STATE_ENDED"
                else -> "UNKNOWN_STATE"
            }
            Log.d(TAG, "onPlaybackStateChanged: state=$stateString")
            super.onPlaybackStateChanged(playbackState)
            printPlayerTimeLine("onPlaybackStateChanged:")
        }

        override fun onRenderedFirstFrame() {
            super.onRenderedFirstFrame()
            printPlayerTimeLine("onRenderedFirstFrame:")
        }

        override fun onPlayerError(error: PlaybackException) {
            super.onPlayerError(error)
            printPlayerTimeLine("onPlayerError:")
            error.printStackTrace()
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        videoUri = arguments?.getString(EXO_URI)
        val root = inflater.inflate(R.layout.exo_player_fragment, container, false)
        val playerView = root.findViewById<StyledPlayerView>(R.id.styled_player_view)
        initPlayerView(playerView)
        return root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        startPlay()
    }

    private fun initPlayerView(playerView: StyledPlayerView) {
        Log.d(TAG, "initPlayerView: ")
        player = ExoPlayer.Builder(requireContext()).build()
        player?.addListener(listener)
        // Bind the player to the view.
        playerView.player = player

        // back
        playerView.findViewById<View>(R.id.back).setOnClickListener {
            fragmentManager?.popBackStack()
            val ft = fragmentManager?.beginTransaction()
            ft?.remove(this@ExoPlayerFragment)
            ft?.commitAllowingStateLoss()
        }
    }

    private var prepareTime: Long = 0L
    private fun printPlayerTimeLine(method: String) {
        val c = System.currentTimeMillis()
        val duration = if (prepareTime == 0L) 0 else c - prepareTime
        prepareTime = c
        Log.i(TAG, "printPlayerTimeLine: method=$method, duration=$duration, uri=${videoUri}")
    }

    private fun startPlay() {
        Log.d(TAG, "startPlay: ")
        videoUri?.let {
            // Build the media item.
            val mediaItem: MediaItem = MediaItem.fromUri(it)

            // Set the media item to be played.
            player?.setMediaItem(mediaItem)

            // Prepare the player.
            player?.prepare()
            printPlayerTimeLine("player->prepare:")

            // Start the playback.
            player?.play()
//            calPlayerTimeLine("player->play:")
        }
    }

    override fun onDestroy() {
        player?.release()
        super.onDestroy()
    }
}

import android.app.Activity
import android.content.Context
import android.graphics.Point
import android.os.Build
import android.view.View
import android.view.ViewGroup
import android.view.WindowManager

/**
* 工具类，提供了系统栏高度和屏幕宽高获取方法
*/
object SystemBarUtil {

    /**
     * 获取状态栏高度
     */
    @JvmStatic
    fun getStatusBarHeight(context: Context): Int {
        var height = 0
        try {
            val resourceId = context.applicationContext.resources.getIdentifier(
                "status_bar_height",
                "dimen",
                "android"
            )
            if (resourceId > 0) {
                height =
                    context.applicationContext.resources.getDimensionPixelSize(resourceId)
            }
        } catch (e: Exception) {
        }
        return height
    }

    /**
     * 获取系统导航栏高度
     */
    @JvmStatic
    fun getNavigationBarHeight(context: Context): Int {
        var height = 0
        try {
            val resourceId = context.applicationContext.resources.getIdentifier(
                "navigation_bar_height",
                "dimen",
                "android"
            )
            if (resourceId > 0) {
                height =
                    context.applicationContext.resources.getDimensionPixelSize(resourceId)
            }
        } catch (e: Exception) {
        }
        return height
    }

    private const val NAVIGATION = "navigationBarBackground"

    // 该方法需要在View完全被绘制出来之后调用
    @JvmStatic
    private fun isNavigationBarVisible(activity: Activity): Boolean {
        val vp = activity.window.decorView as ViewGroup?
        if (vp != null) {
            for (i in 0 until vp.childCount) {
                vp.getChildAt(i).context.packageName
                if (vp.getChildAt(i).id !== View.NO_ID &&
                    NAVIGATION == activity.resources.getResourceEntryName(vp.getChildAt(i).id)
                ) {
                    return true
                }
            }
        }
        return false
    }

    /**
     * 获取屏幕的物理大小 px
     */
    @JvmStatic
    fun getDeviceScreenSize(context: Context): Point {
        val appContext = context.applicationContext
        val wm = appContext.getSystemService(Context.WINDOW_SERVICE) as WindowManager
        val point = Point(0, 0)
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
            wm.defaultDisplay.getRealSize(point)
        } else {
            wm.defaultDisplay.getSize(point)
        }
        return point
    }

    /**
     * 获取显示屏幕的宽高 px
     */
    @JvmStatic
    fun getDisplaySize(context: Context): Point {
        val point = Point(0, 0)
        val dm = context.applicationContext.resources.displayMetrics
        point.x = dm.widthPixels
        point.y = dm.heightPixels
        return point
    }
}