multiplplanes.kt

private fun flyPlane(plane: ImageView, pathMeasure: PathMeasure) {
        var distance = 0f
        val tan = floatArrayOf(0f,0f)
        val pos = floatArrayOf(0f, 0f)
        val valueAnimator = ValueAnimator.ofFloat(0f, 1f)
        // fly planes with different speed so that they look separately on the screen
        valueAnimator.duration = (pathMeasure.length * random.nextInt(3,8)).toLong()
        valueAnimator.interpolator = AccelerateDecelerateInterpolator()
        valueAnimator.addUpdateListener {
            distance = it.animatedValue as Float
            pathMeasure.getPosTan(distance * pathMeasure.length, pos, tan)
            val planeX = pos[0]
            val planeY = pos[1]
            plane.x = planeX
            plane.y = planeY
            val degrees = atan2(tan[1], tan[0]) * 180.0 / Math.PI
            plane.rotation = degrees.toFloat() - 180
        }
        valueAnimator.doOnEnd {
            if (pathMeasure.nextContour()) {
                flyPlane(plane, pathMeasure)
            }
        }
        valueAnimator.start()
    }