使用AS3编写。 宽高动态指定。 增加滚动条背景点击事件。 消除了鼠标滚轮无法同时准确控制多个文本框的重大BUG。

源文件下载
使用方法见源文件
为了方便懒人，直接帖一下代码：
package com.qoolu.component
{
import flash.events.MouseEvent;
import flash.events.Event;
import flash.display.SimpleButton;
import flash.text.TextField;
import flash.display.Sprite;
import flash.utils.getTimer;
import flash.geom.Rectangle;
/**
* @author 寂寞火山:[url]http://www.huoshan.org[/url]
* @version V5 [08.3.15]
* 动态文本滚动条
*/
public class ScrollBar extends Sprite {
//=============本类属性==============
////接口元件
private var scrollText : TextField;
private var scrollBar_sprite : Sprite;
private var up_btn : SimpleButton;
private var down_btn : SimpleButton;
private var pole_sprite : Sprite;
private var bg_sprite : Sprite;
////初始数据
private var poleStartHeight : Number;
private var poleStartY : Number;
private var totalPixels : Number;
private var isSelect : Boolean;
////上下滚动按钮按钮下时间
private var putTime : Number;
/**
* @param scrollText_fc:被滚动的文本框
* @param scrollBarMc_fc：舞台上与本类所代理的滚动条元件
* @param height_fc：滚动条高
* @param width_fc：滚动条宽
*/
public function ScrollBar(scrollText_fc : TextField, scrollBarMc_fc : Sprite, height_fc : uint = 0,width_fc : uint = 0) {
//——————滚动条_sprite，滚动条按钮和滑块mc，被滚动的文本域初始化
scrollText = scrollText_fc;
scrollBar_sprite = scrollBarMc_fc;
up_btn = SimpleButton(scrollBar_sprite.getChildByName("up_btn"));
down_btn = SimpleButton(scrollBar_sprite.getChildByName("down_btn"));
pole_sprite = Sprite(scrollBar_sprite.getChildByName("pole_mc"));
bg_sprite = Sprite(scrollBar_sprite.getChildByName("bg_mc"));

//——————可用性控制
pole_sprite.visible = false;
up_btn.enabled = false;
down_btn.enabled = false;

//——————其他属性初始化
bg_sprite.useHandCursor = false;
isSelect = scrollText.selectable;
if(height_fc == 0) {
bg_sprite.height = scrollText.height;
}else {
bg_sprite.height = height_fc;
}
if(width_fc != 0) {
bg_sprite.width = width_fc 2;
pole_sprite.width = width_fc;
up_btn.width = up_btn.height = down_btn.width = down_btn .height = width_fc;
}
down_btn.y = bg_sprite.y bg_sprite.height - down_btn.height - 1;
poleStartHeight = Math.floor(down_btn.y - up_btn.y - up_btn.height);
poleStartY = pole_sprite.y = Math.floor(up_btn.y up_btn.height);

//——————注册侦听器
//文本滚动与鼠标滚轮
scrollText.addEventListener(Event.SCROLL, textScroll);
scrollText.addEventListener(MouseEvent.MOUSE_WHEEL, mouseWheel);
//上滚动按钮
up_btn.addEventListener(MouseEvent.MOUSE_DOWN, upBtn);
up_btn.stage.addEventListener(MouseEvent.MOUSE_UP, upBtnUp);
//下滚动按钮
down_btn.addEventListener(MouseEvent.MOUSE_DOWN, downBtn);
down_btn.stage.addEventListener(MouseEvent.MOUSE_UP, downBtnUp);
//滑块
pole_sprite.addEventListener(MouseEvent.MOUSE_DOWN, poleSprite);
pole_sprite.stage.addEventListener(MouseEvent.MOUSE_UP, poleUp);
//滑块背景点击
bg_sprite.addEventListener(MouseEvent.MOUSE_DOWN, bgDown);
}
/**
* 文本滚动事件
*/
private function textScroll(event : Event) : void {
//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(scrollText.maxScrollV != 1) {
pole_sprite.visible = true;
up_btn.enabled = true;
down_btn.enabled = 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 heightVar : Number = 1 - (scrollText.maxScrollV - 1) / scrollText.maxScrollV;
//根据高度因子初始化滑块的高度
pole_sprite.height = Math.floor(poleStartHeight * Math.pow(heightVar, 1 / 3));
totalPixels = Math.floor(down_btn.y - up_btn.y - up_btn.height - pole_sprite.height);
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
}else {
pole_sprite.visible = false;
up_btn.enabled = false;
down_btn.enabled = false;
}
}
/**
* 滑块滚动
*/
private function poleSprite(event : MouseEvent) : void {
//首先取消文本框滚动侦听，因为文本滚动的时候会设置滑块的位置，而此时是通过滑块调整文本的位置，所以会产生冲突
scrollText.removeEventListener(Event.SCROLL, textScroll);
//监听舞台，这样可以保证拖动滑竿的时候，鼠标在舞台的任意位置松手，都会停止拖动
scrollBar_sprite.stage.addEventListener(MouseEvent.MOUSE_UP, poleUp);
//限定拖动范围
var dragRect : Rectangle = new Rectangle(pole_sprite.x, poleStartY, 0, totalPixels);
pole_sprite.startDrag(false, dragRect);
scrollBar_sprite.addEventListener(Event.ENTER_FRAME, poleDown);
}
private function poleDown(event : Event) : void {
//在滚动过程中及时获得滑块所处位置
var nowPosition : Number = Math.floor(pole_sprite.y);
//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？
scrollText.scrollV = (scrollText.maxScrollV - 1) * (nowPosition - poleStartY) / totalPixels 2;
//误差校正
var unitPixels : Number = totalPixels / (scrollText.maxScrollV - 1);
if((nowPosition - poleStartY) < unitPixels) {
scrollText.scrollV = (scrollText.maxScrollV - 1) * (nowPosition - poleStartY) / totalPixels;
}
}
private function poleUp(event : MouseEvent) : void {
pole_sprite.stopDrag();
scrollBar_sprite.removeEventListener(Event.ENTER_FRAME, poleDown);
scrollBar_sprite.stage.removeEventListener(MouseEvent.MOUSE_UP, poleUp);
scrollText.addEventListener(Event.SCROLL, textScroll);
}
/**
* 滑块背景点击
*/
private function bgDown(event : MouseEvent) : void {
var nowPosition : Number;
if((scrollBar_sprite.mouseY - up_btn.y) < (pole_sprite.height / 2)) {
nowPosition = Math.floor(up_btn.y up_btn.height);
}else if((down_btn.y - scrollBar_sprite.mouseY) < pole_sprite.height / 2) {
nowPosition = Math.floor(down_btn.y - pole_sprite.height);
}else {
nowPosition = scrollBar_sprite.mouseY - pole_sprite.height / 2;
}
pole_sprite.y = nowPosition;
scrollText.scrollV = (scrollText.maxScrollV - 1) * (nowPosition - poleStartY) / totalPixels 2;
var unitPixels : Number = totalPixels / (scrollText.maxScrollV - 1);
if((nowPosition - poleStartY) < unitPixels) {
scrollText.scrollV = (scrollText.maxScrollV - 1) * (nowPosition - poleStartY) / totalPixels 1;
}
}
/**
* 下滚动按钮
*/
private function downBtn(event : MouseEvent) : void {
scrollText.scrollV ;
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
//当鼠标在按钮上按下的时间大于设定时间时，连续滚动
putTime = getTimer();
scrollBar_sprite.addEventListener(Event.ENTER_FRAME, downBtnDown);
}
private function downBtnDown(event : Event) : void {
if(getTimer() - putTime > 500) {
scrollText.scrollV ;
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
}
}
private function downBtnUp(event : MouseEvent) : void {
scrollBar_sprite.removeEventListener(Event.ENTER_FRAME, downBtnDown);
}
/**
* 上滚动按钮
*/
private function upBtn(event : MouseEvent) : void {
scrollText.scrollV--;
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
//当鼠标在按钮上按下的时间大于设定时间时，连续滚动
putTime = getTimer();
scrollBar_sprite.addEventListener(Event.ENTER_FRAME, upBtnDown);
}
private function upBtnDown(event : Event) : void {
if(getTimer() - putTime > 500) {
scrollText.scrollV--;
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
}
}
private function upBtnUp(event : MouseEvent) : void {
scrollBar_sprite.removeEventListener(Event.ENTER_FRAME, upBtnDown);
}
/**
* 鼠标滚轮事件
*/
private function mouseWheel(event : MouseEvent) : void {
if(isSelect == false) {
scrollText.scrollV -= Math.floor(event.delta / 2);
}else if(isSelect == true) {
event.delta = 1;
}
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
}
}
}

Flash AS3教程:动态文本滚动条