【備忘録】Androidで魔法を使っているみたいなタッチエフェクト

画面に触るたびに散る光の粉っぽいエフェクト

例

こんな感じのエフェクト。

MyEffect.kt

@SuppressLint("ViewConstructor")
class MyEffect(context: Context, private val eventX: Float, private val eventY: Float): View(context) {
    private var paint = Paint()

    override fun onDraw(canvas: Canvas?) {
        canvas?.drawColor(Color.TRANSPARENT)
        val color = Color.WHITE
        paint.apply {
            setColor(color)
            alpha = 200
            isAntiAlias = true
            style = Paint.Style.FILL
        }
        canvas?.drawCircle(eventX, eventY, 2f, paint)
        for (count in 1..4) {
            val scatter1 = (-30..30).random().toFloat()
            val scatter2 = (-30..30).random().toFloat()
            val size = (1..6).random().toFloat()
            canvas?.drawCircle(eventX + scatter1, eventY + scatter2, size, paint)
        }
    }
}

MainActivity.kt

 override fun onTouchEvent(event: MotionEvent?): Boolean {
        if (event?.action == MotionEvent.ACTION_UP || event?.action == MotionEvent.ACTION_MOVE) {
            val myEffect = MyEffect(this, event.x, event.y)
            binding.parentLayout.addView(myEffect)
            myEffect.run {
                animate().alpha(0f).setDuration(800)
            }
            handler.postDelayed({ binding.parentLayout.removeView(myEffect) }, 810)
            return true
        }
        return false
    }