计算两条直线的交点

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/vcshcn/article/details/82557770

    static public Point2D getNodeCross(AbstractNode start, AbstractNode end) {
        Line line = new Line(start.getLayoutX()+start.getWidth()/2, start.getLayoutY()+start.getHeight()/2, end.getLayoutX()+end.getWidth()/2, end.getLayoutY()+end.getHeight()/2);
        LineModal me = new LineModal(line);
        LineModal left = new LineModal(end.getLayoutX(), end.getLayoutY(), end.getLayoutX(), end.getLayoutY() + end.getHeight());
        LineModal top = new LineModal(end.getLayoutX(), end.getLayoutY(), end.getLayoutX()+end.getWidth(), end.getLayoutY());
        LineModal right = new LineModal(end.getLayoutX()+end.getWidth(), end.getLayoutY(), end.getLayoutX()+end.getWidth(), end.getLayoutY()+end.getHeight());
        LineModal bottom = new LineModal(end.getLayoutX(), end.getLayoutY()+end.getHeight(), end.getLayoutX()+end.getWidth(), end.getLayoutY()+end.getHeight());

        double x00 = top.x1;
        double x11 = top.x2;
        double y00 = left.y1;
        double y11 = left.y2;
        
        Vector<Point2D> v = new Vector<>();
        
        Point2D p =left.getIntersection(me);
        if (p != null && y00 <= p.getY() && p.getY() <= y11) {
            v.add(p);
        }
        
        p = top.getIntersection(me);
        if (p != null && x00 <= p.getX() && p.getX() <= x11) {
            v.add(p);
        }
        
        p = right.getIntersection(me);
        if (p != null && y00 <= p.getY() && p.getY() <= y11) {
            v.add(p);
        }

        p = bottom.getIntersection(me);
        if (p != null && x00 <= p.getX() && p.getX() <= x11) {
            v.add(p);
        }

        if (v.size() > 0) {
            Point2D min = v.get(0);
            for (Point2D pp : v) {
                if (pp.distance(line.getStartX(), line.getStartY()) < min.distance(line.getStartX(), line.getStartY())) {
                    min = pp; 
                }
            }
            return min;
        }
        throw new java.lang.NullPointerException();
    }
}

class LineModal {
	protected double x1, y1, x2, y2;
	protected double a,b,c;

    public LineModal(Line p ) {
        this(p.getStartX(), p.getStartY(), p.getEndX(), p.getEndY());
    }
    
    public LineModal(double x0, double y0, double x1, double y1 ) {
        this.x1 = x0;
        this.y1 = y0;
        this.x2 = x1;
        this.y2 = y1;
        a = y1 - y0;
        b = x0 - x1;
        c = x1 * y0 - x0 * y1;
    }

    public Point2D getIntersection(LineModal _other) {
        LineModal other = (LineModal)_other;
        double x = (other.c * b - c * other.b ) /  ( a * other.b - other.a * b );
        double y = (other.c * a - c * other.a ) /  ( b * other.a - other.b * a );

        return new Point2D(x, y);
    }

	@Override
	public String toString() {
        return "Line[" + x1 + "," + y1 + " - " + x2 + "," + y2 + "]" ;
	}
}

经过计算后,会计算出两条直线的交点