TimeLineView.kt

 BackgroundExecutor.execute(object : BackgroundExecutor.Task("", 0L, "") {
            override fun execute() {
                try {
                    val threshold = 11
                    val thumbnailList = LongSparseArray<Bitmap>()
                    val mediaMetadataRetriever = MediaMetadataRetriever()
                    mediaMetadataRetriever.setDataSource(context, mVideoUri)
                    val videoLengthInMs = (Integer.parseInt(mediaMetadataRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION)) * 1000).toLong()
                    val frameHeight = mHeightView
                    val initialBitmap = mediaMetadataRetriever.getFrameAtTime(0, MediaMetadataRetriever.OPTION_CLOSEST_SYNC)
                    val frameWidth = ((initialBitmap.width.toFloat() / initialBitmap.height.toFloat()) * frameHeight.toFloat()).toInt()
                    var numThumbs = ceil((viewWidth.toFloat() / frameWidth)).toInt()
                    if (numThumbs < threshold) numThumbs = threshold
                    val cropWidth = viewWidth / threshold
                    val interval = videoLengthInMs / numThumbs
                    for (i in 0 until numThumbs) {
                        var bitmap = mediaMetadataRetriever.getFrameAtTime(i * interval, MediaMetadataRetriever.OPTION_CLOSEST_SYNC)
                        if (bitmap != null) {
                            try {
                                bitmap = Bitmap.createScaledBitmap(bitmap, frameWidth, frameHeight, false)
                                bitmap = Bitmap.createBitmap(bitmap, 0, 0, cropWidth, bitmap.height)
                            } catch (e: Exception) {
                                e.printStackTrace()
                            }
                            thumbnailList.put(i.toLong(), bitmap)
                        }
                    }
                    mediaMetadataRetriever.release()
                    returnBitmaps(thumbnailList)
                } catch (e: Throwable) {
                    Thread.getDefaultUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e)
                }
            }
        })