文本框滚动缓冲效果

效果如下:

今天写了这个效果的代码
用在主页的diary里
觉得以前用scroll对象来控制文本框，滚动起来比较生硬

其中drag为滚动条名字
block为文本框
b_up,b_down为上下滚动按钮

主要方法是用block始终跟随drag的位置变化而滚动
而b_up,b_down还有鼠标滚轮都是直接控制drag的位置变化的，从而间接控制文本框的滚动

            // JTL
            // http://www.hartech.cn
            // e-mail: jtl.zheng@gmail.com
            //初始化函数
            function Var() {
            //滚动条与上下按钮的间隙
            space = 31;
            //上下按钮的滚动速度
            updown_speed = 5;
            //文本框的滚动范围
            block_range = block._height-mark._height;
            //文本框的初始位置
            block_origin = block._y;
            //滚动条的滚动范围
            drag_range = b_down._y-b_up._y-2*space;
            //滚动条的初始位置
            drag_origin = b_up._y+space;
            //初始化滚动条位置
            drag._y = drag_origin;
            //滚动缓冲系数
            k = .1;
            }
           Var();
           //block为文本框，始终跟随滚动条（drag）变化
            block.onEnterFrame = function() {
            //pos为文本框目标位置
            pos = block_origin-(drag._y-drag_origin)*block_range/drag_range;
            //缓冲效果
            this._y += (pos-this._y)*k;
            };
           drag.onPress = function() {
            this.startDrag(false, this._x, drag_origin, this._x, (drag_origin+drag_range));
            };
           drag.onRelease = function() {
            this.stopDrag();
            };
           //up_down按钮
            b_up.onPress = function() {
            onEnterFrame = function () {
            if (drag._y<=drag_origin) {
            drag._y = drag_origin;
            } else {
            drag._y -= updown_speed;
            }
            };
            };
            b_up.onRelease = function() {
            onEnterFrame = null;
            };
            b_down.onPress = function() {
            onEnterFrame = function () {
            if (drag._y>=drag_origin+drag_range) {
            drag._y = drag_origin+drag_range;
            } else {
            drag._y += updown_speed;
            }
            };
            };
            b_down.onRelease = function() {
            onEnterFrame = null;
            };
            //侦听mouse滚轮
            mouseListener = new Object();
            mouseListener.onMouseWheel = function(delta) {
            if (delta>0) {
            drag._y -= updown_speed*2;
            }
            if (delta<0) {
            drag._y += updown_speed*2;
            }
            if (drag._y<=drag_origin) {
            drag._y = drag_origin;
            }
            if (drag._y>=drag_origin+drag_range) {
            drag._y = drag_origin+drag_range;
            }
            };
            Mouse.addListener(mouseListener);
           

建立文本框代码

		   loadVariables("text/diary.txt", this);
		   myTextFormat = new TextFormat();
		   myTextFormat.font = "宋体";
		   myTextFormat.size = 12;
		   myTextFormat.leading = 3;
		   createTextField("test_txt", 10, 0, 0, 210, 10);
		   test_txt.multiline = true;
		   test_txt.wordWrap = true;
		   test_txt.autoSize = true;
		   test_txt.html = true;
		   test_txt.htmlText = text;
		   test_txt.setTextFormat(myTextFormat);
		   test_txt.type = "Static";
		   // 演示地址：
		   // http://www.hartech.cn/blog/blogview.asp?logID=45