用纯AS写了个滚动条

代码如下:

下面是所有的AS代码：
//%%%%%%%%%%%%MC类自定义方法%%%%%%%%%%%%//
//——————绘图方法————//
//三角型方法
MovieClip.prototype.sanjiaoxing = function(zuobiao1, zuobiao2, zuobiao3, bangzhi, yanse, toumingdu) {
       this.lineStyle(bangzhi, yanse, toumingdu);
       this.moveTo(zuobiao1.x, zuobiao1.y);
       this.lineTo(zuobiao2.x, zuobiao2.y);
       this.lineTo(zuobiao3.x, zuobiao3.y);
       this.lineTo(zuobiao1.x, zuobiao1.y);
};
//宽高矩形法，根据初始点坐标和宽与高确定矩形。x，y为初始点坐标，kuan和gao为矩形的宽和高。
MovieClip.prototype.changkuanjuxing = function(x, y, kuan, gao, bangzhi, yanse, toumingdu) {
       this.lineStyle(bangzhi, yanse, toumingdu);
       this.moveTo(x, y);
       this.lineTo(x+kuan, y);
       this.lineTo(x+kuan, y+gao);
       this.lineTo(x, y+gao);
       this.lineTo(x, y);
};
//中心点矩形法，根据中心点的坐标和宽与高确定矩形。x，y为中心点坐标，kuan，gao为矩形的长和宽。
MovieClip.prototype.zhongxinjuxing = function(x, y, kuan, gao, bangzhi, yanse, toumingdu) {
       this.lineStyle(bangzhi, yanse, toumingdu);
       this.moveTo(x-kuan/2, y+gao/2);
       this.lineTo(x+kuan/2, y+gao/2);
       this.lineTo(x+kuan/2, y-gao/2);
       this.lineTo(x-kuan/2, y-gao/2);
       this.lineTo(x-kuan/2, y+gao/2);
};
//————定位方法————//
MovieClip.prototype.dingwei = function(x, y) {
       this._x = x;
       this._y = y;
};
//————上色方法————//
//定义一个获取颜色值，并把它转化成16进制的函数       
//获取颜色值的后六位，使此方法可以同时满足“#FFFFFF”和“0xFFFFFF”两种格式的颜色值
function jinzhizhuanhuan(yansezhi) {
       var yansezhi = yansezhi.substr(-6, 6);
       return parseInt(yansezhi, 16);
}
Color.prototype.shangse = function(yansezhi) {
       this.setRGB(jinzhizhuanhuan(yansezhi));
};
MovieClip.prototype.shangse = function(yansezhi) {
       var linshi_color = new Color(this);
       linshi_color.shangse(yansezhi);
};
//%%%%%%%%%%%加载XML文档%%%%%%%%%%%%%//
gundongtiao_xml = new XML();
gundongtiao_xml.ignoreWhite = true;
gundongtiao_xml.load("gundongtiao.xml");
gundongtiao_xml.onLoad = function() {
       var jiedianlujing_xml = gundongtiao_xml.firstChild.childNodes;
       //滚动条背景参数
       with (jiedianlujing_xml[0]) {
              var gundongtiaobeijingse = jinzhizhuanhuan(attributes["背景色"]);
              var gundongtiaotoumingdu = attributes["背景透明度"];
              var gundongtiaobiankuangse = jinzhizhuanhuan(attributes["边框色"]);
              var gundongtiaobiankuangtoumingdou = attributes["边框透明度"];
              var gundongtiaobiankuangcuxi = attributes["边框粗细"];
              var gundongtiaokuan = attributes["宽"];
       }
       //方块参数
       with (jiedianlujing_xml[1]) {
              var fangkuaibeijingse = jinzhizhuanhuan(attributes["背景色"]);
              var fangkuaitoumingdu = attributes["背景透明度"];
              var fangkuaibiankuangse = jinzhizhuanhuan(attributes["边框色"]);
              var fangkuaibiankuangtoumingdou = attributes["边框透明度"];
              var fangkuaibiankuangcuxi = attributes["边框粗细"];
       }
       //三角参数
       with (jiedianlujing_xml[2]) {
              var sanjiaoyuanshise = jinzhizhuanhuan(attributes["原始色"]);
              var sanjiaohuodongse = jinzhizhuanhuan(attributes["活动色"]);
              //记录下原始色和活动色，以备在“上”，“下”按钮中使用
              jiluyuanshise = attributes["原始色"];
              jiluhuodongse = attributes["活动色"];
              var sanjiaotoumingdou = attributes["透明度"];
       }
       //滑块参数
       with (jiedianlujing_xml[3]) {
              var huakuaibeijingse = jinzhizhuanhuan(attributes["背景色"]);
              var huakuaitoumingdu = attributes["背景透明度"];
              var huakuaibiankuangse = jinzhizhuanhuan(attributes["边框色"]);
              var huakuaibiankuangtoumingdou = attributes["边框透明度"];
              var huakuaibiankuangcuxi = attributes["边框粗细"];
       }
       //先根据文本域的高确定滚动条的高
       gundongtiaogao = wenben_txt._height;
       ////////////中心法绘制滚动条背景矩形条
       createEmptyMovieClip("gundongtiao_mc", 1000);
       gundongtiao_mc.beginFill(gundongtiaobeijingse, gundongtiaotoumingdu);
       gundongtiao_mc.zhongxinjuxing(0, 0, gundongtiaokuan, gundongtiaogao, gundongtiaobiankuangcuxi, gundongtiaobiankuangse, gundongtiaobiankuangtoumingdou);
       gundongtiao_mc.endFill();
       //根据文本域的位置确定滚动条位置，使其紧贴在文本域的右端
       gundongtiao_mc.dingwei(wenben_txt._x+wenben_txt._width+gundongtiao_mc._width/2, wenben_txt._y+wenben_txt._height/2);
       /////////中心点矩形法绘制滚动条上下按钮
       //////绘制上按钮背景方块
       gundongtiao_mc.createEmptyMovieClip("shangfangkuai_mc", 1);
       gundongtiao_mc.shangfangkuai_mc.beginFill(fangkuaibeijingse, fangkuaitoumingdu);
       gundongtiao_mc.shangfangkuai_mc.zhongxinjuxing(0, 0, gundongtiao_mc._width, gundongtiao_mc._width, fangkuaibiankuangcuxi, fangkuaibiankuangse, fangkuaitoumingdu);
       gundongtiao_mc.shangfangkuai_mc.endFill();
       //定位上按钮背景方块
       gundongtiao_mc.shangfangkuai_mc.dingwei(0, -gundongtiao_mc._height/2+gundongtiao_mc.shangfangkuai_mc._height/2);
       //////绘制上按钮三角形
       gundongtiao_mc.createEmptyMovieClip("shangsanjiao_mc", 2);
       //中心点法绘制三角形
       //首先定义一个因子，此因子等于正三角形中心到各顶点的距离，用来定位三角形各顶点的位置。
       var yinzi = gundongtiaokuan/3;
       var zuobiao1x = -1/2*Math.pow(3, 1/2)*yinzi;
       var zuobiao1y = 1/2*yinzi;
       var zuobiao2x = 1/2*Math.pow(3, 1/2)*yinzi;
       var zuobiao2y = 1/2*yinzi;
       var zuobiao3x = 0;
       var zuobiao3y = -yinzi;
       var zuobiao1 = {x:zuobiao1x, y:zuobiao1y};
       var zuobiao2 = {x:zuobiao2x, y:zuobiao2y};
       var zuobiao3 = {x:zuobiao3x, y:zuobiao3y};
       gundongtiao_mc.shangsanjiao_mc.beginFill(sanjiaoyuanshise, sanjiaotoumingdou);
       gundongtiao_mc.shangsanjiao_mc.sanjiaoxing(zuobiao1, zuobiao2, zuobiao3, 1, 0x000000, 0);
       gundongtiao_mc.shangsanjiao_mc.endFill();
       //定位上三角形
       gundongtiao_mc.shangsanjiao_mc.dingwei(0, -gundongtiao_mc._height/2+gundongtiao_mc.shangfangkuai_mc._height/2);
       //////复制上按钮背景方块和三角形，并定位于下方
       //复制下方块
       gundongtiao_mc.shangfangkuai_mc.duplicateMovieClip("xiafangkuai_mc", 3);
       //定位下按钮背景方块，这里的Y坐标加一，是为了让下方块跟文本框底部对齐！
       gundongtiao_mc.xiafangkuai_mc.dingwei(0, Math.floor(gundongtiao_mc._height/2-gundongtiao_mc.xiafangkuai_mc._height/2)+1);
       //复制下三角形
       gundongtiao_mc.shangsanjiao_mc.duplicateMovieClip("xiasanjiao_mc", 4);
       //旋转180度
       gundongtiao_mc.xiasanjiao_mc._rotation = 180;
       //定位下三角形
       gundongtiao_mc.xiasanjiao_mc.dingwei(0, gundongtiao_mc._height/2-gundongtiao_mc.xiafangkuai_mc._height/2);
       ///////////绘制滑块
       //长宽矩形法绘制滑块矩形
       gundongtiao_mc.createEmptyMovieClip("huakuai_mc", 5);
       gundongtiao_mc.huakuai_mc.beginFill(huakuaibeijingse, huakuaitoumingdu);
       gundongtiao_mc.huakuai_mc.changkuanjuxing(-gundongtiao_mc._width/2, 0, gundongtiao_mc._width, gundongtiao_mc._width, huakuaibiankuangcuxi, huakuaibiankuangse, huakuaibiankuangtoumingdou);
       gundongtiao_mc.huakuai_mc.endFill();
       //---------滚动初始化---------//
       //滑块的初始高度，并记录
       chushigaodu = Math.floor(gundongtiao_mc.xiafangkuai_mc._y-gundongtiao_mc.shangfangkuai_mc._y-gundongtiao_mc.shangfangkuai_mc._height);
       //初始化滑块Y坐标，并记录
       ychushiweizhi = gundongtiao_mc.huakuai_mc._y=Math.round(gundongtiao_mc.shangfangkuai_mc._y+gundongtiao_mc.shangfangkuai_mc._height/2);
       //小滑块不可见
       gundongtiao_mc.huakuai_mc._visible = false;
};
//%%%%%%%%%%%%%%%%滚动代码%%%%%%%%%%%%%%%%%%//
//////////为父剪辑的文字域注册侦听器，以侦听在文字域产生变化时，也就是在文本被载入进来时，执行下面的代码。这样就不用担心代码执行顺序问题！
var zhentingqi = new Object();
wenben_txt.addListener(zhentingqi);
//当文字域载入完成时，为什么触发onScroller事件，而不是onChange事件？
zhentingqi.onScroller = function() {
       trace("-------------------------");
       trace("滚动总行数="+wenben_txt.maxscroll);
       trace("当前行="+wenben_txt.scroll);
       //判断滑块儿是否显示，并根据文本内容多少定义滑块高度
       if (_parent.wenben_txt.maxscroll != 1) {
              gundongtiao_mc.huakuai_mc._visible = true;
              //定义一个高度因子，此因子随加载文本的增多，将无限趋向于1。
              var gaoduyinzi = 1-(wenben_txt.maxscroll-1.5)/wenben_txt.maxscroll;
              //初始化滑块的高度，它的最小高度定义为2象素。
              gaodu = gundongtiao_mc.huakuai_mc._height=Math.floor(chushigaodu*Math.pow(gaoduyinzi, 1/6));
              trace("滑块高="+gaodu);
       }
       //滑块滚动的总象素数
       var zongxiangsu = gundongtiao_mc.xiafangkuai_mc._y-gundongtiao_mc.shangfangkuai_mc._y-gundongtiao_mc.shangfangkuai_mc._height-gundongtiao_mc.huakuai_mc._height;
       //定义平均象素,每一行所包含的像素数，即文本域每滚动一行，滑块需要移动的象素数。              
       var pingjunxiangsu = zongxiangsu/(wenben_txt.maxscroll-1);
       //定义平均行数,每一像素包含的行数，即滑块每移动一象素，文本域在理论上应当滚动的行数（尽管非整数行在视觉上没有反映）。
       var pingjunhangshu = (wenben_txt.maxscroll-1)/Math.floor(zongxiangsu);
       trace("滚动总象素="+zongxiangsu);
       trace("平均象素值="+pingjunxiangsu);
       ///////////定义上按钮
       gundongtiao_mc.shangfangkuai_mc.onRollOver = function() {
              gundongtiao_mc.shangsanjiao_mc.shangse(jiluhuodongse);
              this.onPress = function() {
                     this.onEnterFrame = function() {
                            wenben_txt.scroll--;
                            // 使滑块儿移动到相应的位置。
                            gundongtiao_mc.huakuai_mc._y = ychushiweizhi+pingjunxiangsu*(wenben_txt.scroll-1);
                            trace("滑块Y坐标="+gundongtiao_mc.huakuai_mc._y);
                     };
              };
              this.onRelease = function() {
                     delete this.onEnterFrame;
              };
              this.onRollOut = function() {
                     gundongtiao_mc.shangsanjiao_mc.shangse(jiluyuanshise);
              };
       };
       ////////////定义下按钮
       gundongtiao_mc.xiafangkuai_mc.onRollOver = function() {
              gundongtiao_mc.xiasanjiao_mc.shangse(jiluhuodongse);
              this.onPress = function() {
                     this.onEnterFrame = function() {
                            wenben_txt.scroll++;
                            //使滑块儿移动到相应的位置。       
                            gundongtiao_mc.huakuai_mc._y = ychushiweizhi+pingjunxiangsu*(wenben_txt.scroll-1);
                            trace("滑块Y坐标="+gundongtiao_mc.huakuai_mc._y);
                     };
              };
              this.onRelease = function() {
                     delete this.onEnterFrame;
              };
              this.onRollOut = function() {
                     gundongtiao_mc.xiasanjiao_mc.shangse(jiluyuanshise);
              };
       };
       ///////////换用MOUSE对象的onMouseWheel方法结合侦听器实现滑块随鼠标滚球滚动
       mouseListener = new Object();
       Mouse.addListener(mouseListener);
       mouseListener.onMouseWheel = function(delta) {
              delta = 1;
              gundongtiao_mc.huakuai_mc._y = ychushiweizhi+pingjunxiangsu*(wenben_txt.scroll-1);
       };
       ///////////滑块MC事件处理，当鼠标经过或按下时
       gundongtiao_mc.huakuai_mc.onPress = function() {
              //开始拖动
              this.startDrag(false, this._x, ychushiweizhi, this._x, Math.round(gundongtiao_mc.xiafangkuai_mc._y-gundongtiao_mc.xiafangkuai_mc._height/2-gundongtiao_mc.huakuai_mc._height));
              //使文本随滑块滚动
              this.onEnterFrame = function() {
                     //在滚动过程中即时获得“滑块所处位置”
                     var xianzaiweizhi = Math.floor(this._y);
                     trace("现在位置="+xianzaiweizhi);
                     //使文本随滚动条滚动,这里为什么要加1，可见scroll属性值应该是取正的，也就是说它会删除小数部分，而非采用四舍五入制？
                     wenben_txt.scroll = (xianzaiweizhi-ychushiweizhi)*pingjunhangshu+1;
                     trace("scroll值="+Math.floor((xianzaiweizhi-ychushiweizhi)*pingjunhangshu+1));
                     trace("初始位置="+ychushiweizhi);
                     trace("现在位置="+xianzaiweizhi);
              };
       };
       //滑块MC事件处理，鼠标移出或释放时
       gundongtiao_mc.huakuai_mc.onRollOut = gundongtiao_mc.huakuai_mc.onRelease=function () {
              // “滑块”停止拖动
              this.stopDrag();
              // 停止文本随滑块滚动事件
              delete this.onEnterFrame;
       };
};