使用AS3編寫。 寬高動態指定。 增加滾動條背景點擊事件。 消除了鼠標滾輪無法同時準確控制多個文本框的重大BUG。

源文件下載
使用方法見源文件
為了方便懶人，直接帖一下代碼：
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]
* 動態文本滾動條
*/
public class ScrollBar extends Sprite {
//=============本類屬性==============
////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;
////初始數據
private var poleStartHeight : Number;
private var poleStartY : Number;
private var totalPixels : Number;
private var isSelect : Boolean;
////上下滾動按鈕按鈕下時間
private var putTime : Number;
/**
* @param scrollText_fc:被滾動的文本框
* @param scrollBarMc_fc：舞臺上與本類所代理的滾動條元件
* @param height_fc：滾動條高
* @param width_fc：滾動條寬
*/
public function ScrollBar(scrollText_fc : TextField, scrollBarMc_fc : Sprite, height_fc : uint = 0,width_fc : uint = 0) {
//——————滾動條_sprite，滾動條按鈕和滑塊mc，被滾動的文本域初始化
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;

//——————其他屬性初始化
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);

//——————注冊偵聽器
//文本滾動與鼠標滾輪
scrollText.addEventListener(Event.SCROLL, textScroll);
scrollText.addEventListener(MouseEvent.MOUSE_WHEEL, mouseWheel);
//上滾動按鈕
up_btn.addEventListener(MouseEvent.MOUSE_DOWN, upBtn);
up_btn.stage.addEventListener(MouseEvent.MOUSE_UP, upBtnUp);
//下滾動按鈕
down_btn.addEventListener(MouseEvent.MOUSE_DOWN, downBtn);
down_btn.stage.addEventListener(MouseEvent.MOUSE_UP, downBtnUp);
//滑塊
pole_sprite.addEventListener(MouseEvent.MOUSE_DOWN, poleSprite);
pole_sprite.stage.addEventListener(MouseEvent.MOUSE_UP, poleUp);
//滑塊背景點擊
bg_sprite.addEventListener(MouseEvent.MOUSE_DOWN, bgDown);
}
/**
* 文本滾動事件
*/
private function textScroll(event : Event) : void {
//判斷滑塊兒是否顯示，并根據文本內容多少定義滑塊高度
if(scrollText.maxScrollV != 1) {
pole_sprite.visible = true;
up_btn.enabled = true;
down_btn.enabled = true;
//定義一個高度因子，此因子隨加載文本的增多，將無限趨向于1
var heightVar : Number = 1 - (scrollText.maxScrollV - 1) / scrollText.maxScrollV;
//根據高度因子初始化滑塊的高度
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;
}
}
/**
* 滑塊滾動
*/
private function poleSprite(event : MouseEvent) : void {
//首先取消文本框滾動偵聽，因為文本滾動的時候會設置滑塊的位置，而此時是通過滑塊調整文本的位置，所以會產生沖突
scrollText.removeEventListener(Event.SCROLL, textScroll);
//監聽舞臺，這樣可以保證拖動滑竿的時候，鼠標在舞臺的任意位置松手，都會停止拖動
scrollBar_sprite.stage.addEventListener(MouseEvent.MOUSE_UP, poleUp);
//限定拖動范圍
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 {
//在滾動過程中及時獲得滑塊所處位置
var nowPosition : Number = Math.floor(pole_sprite.y);
//使文本隨滾動條滾動,這里為什么要加1，可見scroll屬性值應該是取正的，也就是說它會刪除小數部分，而非采用四舍五入制？
scrollText.scrollV = (scrollText.maxScrollV - 1) * (nowPosition - poleStartY) / totalPixels 2;
//誤差校正
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);
}
/**
* 滑塊背景點擊
*/
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;
}
}
/**
* 下滾動按鈕
*/
private function downBtn(event : MouseEvent) : void {
scrollText.scrollV ;
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
//當鼠標在按鈕上按下的時間大于設定時間時，連續滾動
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);
}
/**
* 上滾動按鈕
*/
private function upBtn(event : MouseEvent) : void {
scrollText.scrollV--;
pole_sprite.y = Math.floor(poleStartY totalPixels * (scrollText.scrollV - 1) / (scrollText.maxScrollV - 1));
//當鼠標在按鈕上按下的時間大于設定時間時，連續滾動
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);
}
/**
* 鼠標滾輪事件
*/
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));
}
}
}