checkLineClicked.kt

/**
* Check if a point cliked is in the are of a line.
*/
class CheckLineClicked {

    /**
    * Returns the distance between a point(clickPosition) and  a line(start and end point).
    */
    fun checkLineClicked(clickPosition: PointF, startPoint: PointF, endPointF: PointF): Float {
        val x = clickPosition.x
        val y = clickPosition.y
        val x1 = startPoint.x
        val y1 = startPoint.y
        val x2 = endPointF.x
        val y2 = endPointF.y

        return checkLineClicked(x, y, x1, y1, x2, y2)
    }
    
    private fun checkLineClicked(x: Float, y: Float, x1: Float, y1: Float, x2: Float, y2: Float): Float {
        val a = x - x1
        val b = y - y1
        val c = x2 - x1
        val d = y2 - y1

        val dot = a * c + b * d;
        val lenSq = c * c + d * d;
        var param = -1f
        if (lenSq != 0f) //in case of 0 length line
            param = dot / lenSq

        val yy: Float
        val xx: Float

        if (param < 0) {
            xx = x1
            yy = y1
        } else if (param > 1) {
            xx = x2
            yy = y2
        } else {
            xx = x1 + param * c
            yy = y1 + param * d
        }

        val dx = x - xx
        val dy = y - yy
        return sqrt(dx * dx + dy * dy)
    }
}