flex绘制虚线

private function drawDashed(p1:Point,p2:Point,length:Number=5,gap:Number=5):void
   {
    var g:Graphics = this.mainCan.graphics;
    g.lineStyle(1,0);
    var max:Number  = Point.distance(p1,p2);
    var l:Number =0;
    var p3:Point;
    var p4:Point;
    while(l<max)
    {
     p3 = Point.interpolate(p2,p1,l/max);
     l += length;
     if(l>max)
     {
      l = max;
     }
     p4 = Point.interpolate(p2,p1,l / max);
     g.moveTo(p3.x,p3.y);
     g.lineTo(p4.x,p4.y);
     l += gap;
    }
   }s