用ActionScript画虚线

 /*-------------------------------------------------------------
mc.dashTo is a method for drawing dashed (and dotted)
lines. I made this to extend the lineTo function because it
doesn?t have the cutom line types that the in program
line tool has. To make a dotted line, specify a dash length
between .5 and 1.
-------------------------------------------------------------*/
MovieClip.prototype.dashTo = function(startx, starty, endx, endy, len, gap) {
// ==============
// mc.dashTo() - by Ric Ewing (ric@formequalsfunction.com) - version 1.2 - 5.3.2002
//
// startx, starty = beginning of dashed line
// endx, endy = end of dashed line
// len = length of dash
// gap = length of gap between dashes
// ==============
//
// if too few arguments, bail
if (arguments.length < 6) {
return false;
}
// init vars
var seglength, deltax, deltay, segs, cx, cy;
// calculate the legnth of a segment
seglength = len + gap;
// calculate the length of the dashed line
deltax = endx - startx;
deltay = endy - starty;
delta = Math.sqrt((deltax * deltax) + (deltay * deltay));
// calculate the number of segments needed
segs = Math.floor(Math.abs(delta / seglength));
// get the angle of the line in radians
radians = Math.atan2(deltay,deltax);
// start the line here
cx = startx;
cy = starty;
// add these to cx, cy to get next seg start
deltax = Math.cos(radians)*seglength;
deltay = Math.sin(radians)*seglength;
// loop through each seg
for (var n = 0; n < segs; n++) {
this.moveTo(cx,cy);
this.lineTo(cx+Math.cos(radians)*len,cy+Math.sin(radians)*len);
cx += deltax;
cy += deltay;
}
// handle last segment as it is likely to be partial
this.moveTo(cx,cy);
delta = Math.sqrt((endx-cx)*(endx-cx)+(endy-cy)*(endy-cy));
if(delta>len){
// segment ends in the gap, so draw a full dash
this.lineTo(cx+Math.cos(radians)*len,cy+Math.sin(radians)*len);
} else if(delta>0) {
// segment is shorter than dash so only draw what is needed
this.lineTo(cx+Math.cos(radians)*delta,cy+Math.sin(radians)*delta);
}
// move the pen to the end position
this.moveTo(endx,endy);
};