RecordButton_6.kt

private var recordRadius: Float = 0f
private val recordRect = RectF()
private val recordPaint = Paint().apply {
    color = Color.RED
}

override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec)
    if (measuredHeight > 0 && measuredWidth > 0) {
        ...
        recordRadius = radius / 4f
        recordRect.set(cx - recordRadius, cy - recordRadius, cx + recordRadius, cy + recordRadius)
    }
}