SurfaceHolder callback throws when using SimpleExoPlayer from a background thread

This is related to https://github.com/google/ExoPlayer/issues/8843

I create an exo player instance like this.

val playerThread = HandlerThread("video player thread")
playerThread.start()
val handler = Handler(playerThread.looper)
val player = SimpleExoPlayer.Builder(context).setLooper(playerThread.looper).build()

later I add some media items and set the surface

handler.post {
	player.setVideoSurfaceHolder(surfaceView.holder)
    val mediaItem: MediaItem = MediaItem.fromUri(Uri.parse(url))
    playerInfo.player.setMediaItem(mediaItem)
    playerInfo.player.prepare()
    playerInfo.player.play()
}

I also tried just setting the surfaceView, but that gives the same results.

when detached from window

handler.post {
	player.release()
	playerThread.quitSafely()
}

Then I see a stack traces, e.g.

   at com.google.android.exoplayer2.SimpleExoPlayer.verifyApplicationThread(SimpleExoPlayer.java:2028)
        at com.google.android.exoplayer2.SimpleExoPlayer.getCurrentTimeline(SimpleExoPlayer.java:1670)
        at com.google.android.exoplayer2.analytics.AnalyticsCollector.generateEventTime(AnalyticsCollector.java:863)
        at com.google.android.exoplayer2.analytics.AnalyticsCollector.generateEventTime(AnalyticsCollector.java:912)
        at com.google.android.exoplayer2.analytics.AnalyticsCollector.generateReadingMediaPeriodEventTime(AnalyticsCollector.java:920)
        at com.google.android.exoplayer2.analytics.AnalyticsCollector.onSurfaceSizeChanged(AnalyticsCollector.java:492)
        at com.google.android.exoplayer2.SimpleExoPlayer.maybeNotifySurfaceSizeChanged(SimpleExoPlayer.java:1962)
        at com.google.android.exoplayer2.SimpleExoPlayer.access$4100(SimpleExoPlayer.java:92)
        at com.google.android.exoplayer2.SimpleExoPlayer$ComponentListener.surfaceDestroyed(SimpleExoPlayer.java:2280)
        at android.view.SurfaceView.notifySurfaceDestroyed(SurfaceView.java:1830)
        at android.view.SurfaceView.updateSurface(SurfaceView.java:1126)
        at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:306)
        at android.view.View.dispatchDetachedFromWindow(View.java:20525)
        at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:3934)
        at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:3934)
        at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:3934)
        at android.view.ViewGroup.removeViewInternal(ViewGroup.java:5560)
        at android.view.ViewGroup.removeViewAt(ViewGroup.java:5507)
        at androidx.recyclerview.widget.RecyclerView$5.removeViewAt(RecyclerView.java:882)
        at androidx.recyclerview.widget.ChildHelper.removeViewIfHidden(ChildHelper.java:386)
        at androidx.recyclerview.widget.RecyclerView.removeAnimatingView(RecyclerView.java:1452)
        at androidx.recyclerview.widget.RecyclerView$ItemAnimatorRestoreListener.onAnimationFinished(RecyclerView.java:12699)
        at androidx.recyclerview.widget.RecyclerView$ItemAnimator.dispatchAnimationFinished(RecyclerView.java:13199)
        at androidx.recyclerview.widget.SimpleItemAnimator.dispatchMoveFinished(SimpleItemAnimator.java:292)
        at androidx.recyclerview.widget.DefaultItemAnimator$6.onAnimationEnd(DefaultItemAnimator.java:311)
        at android.view.ViewPropertyAnimator$AnimatorEventListener.onAnimationEnd(ViewPropertyAnimator.java:1111)
        at android.animation.Animator$AnimatorListener.onAnimationEnd(Animator.java:554)
        at android.animation.ValueAnimator.endAnimation(ValueAnimator.java:1250)
        at android.animation.ValueAnimator.doAnimationFrame(ValueAnimator.java:1492)
        at android.animation.AnimationHandler.doAnimationFrame(AnimationHandler.java:146)
        at android.animation.AnimationHandler.access$100(AnimationHandler.java:37)
        at android.animation.AnimationHandler$1.doFrame(AnimationHandler.java:54)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:970)
        at android.view.Choreographer.doCallbacks(Choreographer.java:796)
        at android.view.Choreographer.doFrame(Choreographer.java:727)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:957)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7660)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

From the previous bug it looks like because the window of the Surface view is on the main thread. Well of course it is, that’s the only thread it’s allowed to be on.

From what it looks like to me Exo Player doesn’t work when accessed on the non-ui thread when it’s using a surfaceview.

Worse results when using texture view as it doesn’t seem to work at all.

[mpalczew]

In case someone sees this and wants to implement callbacks the way I did.

private class DelegatingSurfaceHolder(
        val surfaceHolder: SurfaceHolder,
        val handler: Handler
    ) : SurfaceHolder {

        private val callbackMap: MutableMap<SurfaceHolder.Callback, DelegatingCallback> =
            mutableMapOf()

        override fun addCallback(callback: SurfaceHolder.Callback?) {
            if (callback != null) {
                val delegatingCallback = DelegatingCallback(
                    callback = callback,
                    handler = handler,
                    holder = this
                )
                callbackMap[callback] = delegatingCallback
                surfaceHolder.addCallback(delegatingCallback)
            }
        }

        override fun removeCallback(callback: SurfaceHolder.Callback?) {
            val delegatingCallback = callbackMap[callback] ?: return
            surfaceHolder.removeCallback(delegatingCallback)
            callbackMap.remove(callback)
        }

        override fun isCreating(): Boolean = surfaceHolder.isCreating()
        override fun setType(type: Int) = surfaceHolder.setType(type)
        override fun setFixedSize(width: Int, height: Int) =
            surfaceHolder.setFixedSize(width, height)
        override fun setSizeFromLayout() = surfaceHolder.setSizeFromLayout()
        override fun setFormat(format: Int) = surfaceHolder.setFormat(format)
        override fun setKeepScreenOn(screenOn: Boolean) = surfaceHolder.setKeepScreenOn(screenOn)
        override fun lockCanvas(): Canvas = surfaceHolder.lockCanvas()
        override fun lockCanvas(dirty: Rect?): Canvas = surfaceHolder.lockCanvas(dirty)
        override fun unlockCanvasAndPost(canvas: Canvas?) =
            surfaceHolder.unlockCanvasAndPost(canvas)
        override fun getSurfaceFrame(): Rect = surfaceHolder.surfaceFrame
        override fun getSurface(): Surface = surfaceHolder.surface
    }

    private class DelegatingCallback(
        val callback: SurfaceHolder.Callback,
        val handler: Handler,
        val holder: SurfaceHolder
    ) : SurfaceHolder.Callback {
        override fun surfaceCreated(holder: SurfaceHolder?) {
            handler.post { callback.surfaceCreated(this.holder) }
        }

        override fun surfaceChanged(holder: SurfaceHolder?, format: Int, width: Int, height: Int) {
            handler.post { callback.surfaceChanged(this.holder, format, width, height) }
        }

        override fun surfaceDestroyed(holder: SurfaceHolder?) {
            val countdownLatch = CountDownLatch(1)
            handler.post {
                callback.surfaceDestroyed(this.holder)
                countdownLatch.countDown()
            }
            countdownLatch.await(1, TimeUnit.SECONDS)
        }
    }

Wrapping the surface holder with what I have here is working for me. Of particular note, DelegatingCallback only implements SufraceHolder.Callback and not Callback2, because that’s what exo implements. Implementing Callback2 and delegating those methods will not work.

[icbaker]

Documentation is updated on dev-v2.