帮忙看下错误：null 为空或不是对象（谢谢）

Question

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="pro.ascx.cs" Inherits="ascx_pro" %>
<style type="text/css"> 
.rollBox{width:421px;overflow:hidden;padding:0;} 
.LeftBotton{height:106px;width:10px;background:url(images/a/y.gif) no-repeat 0 0;overflow:hidden;float:left;display:inline;margin:0 5px 0 5px;cursor:pointer;} 
.RightBotton{height:106px;width:10px;background:url(images/a/z.gif) no-repeat 0 0;overflow:hidden;float:left;display:inline;margin:0 0 0 0;cursor:pointer;} 
.rollBox .Cont{width:800px;overflow:hidden;float:left;} 
.rollBox .ScrCont{width:1000px;} 
.rollBox #List1,.rollBox #List2{float:left;} 
</style>
<script language="javascript" type="text/javascript"> 
<!--//--><![CDATA[//><!-- 
//图片滚动列表 mengjia 070816 
var Speed = 10; //速度(毫秒) 
var Space = 5; //每次移动(px) 
var PageWidth = 327; //翻页宽度 
var fill = 0; //整体移位 
var MoveLock = false; 
var MoveTimeObj; 
var Comp = 0; 
var AutoPlayObj = null; 
GetObj("List2").innerHTML = GetObj("List1").innerHTML; 
GetObj('ISL_Cont').scrollLeft = fill; 
GetObj("ISL_Cont").onmouseover = function(){clearInterval(AutoPlayObj);} 
GetObj("ISL_Cont").onmouseout = function(){AutoPlay();} 
AutoPlay(); 
function GetObj(objName){if(document.getElementById){return eval('document.getElementById("'+objName+'")')}else{return eval('document.all.'+objName)}} 
function AutoPlay(){ //自动滚动 
 clearInterval(AutoPlayObj); 
 AutoPlayObj = setInterval('ISL_GoDown();ISL_StopDown();',3000); //间隔时间 
} 
function ISL_GoUp(){ //上翻开始 
 if(MoveLock) return; 
 clearInterval(AutoPlayObj); 
 MoveLock = true; 
 MoveTimeObj = setInterval('ISL_ScrUp();',Speed); 
} 
function ISL_StopUp(){ //上翻停止 
 clearInterval(MoveTimeObj); 
 if(GetObj('ISL_Cont').scrollLeft % PageWidth - fill != 0){ 
  Comp = fill - (GetObj('ISL_Cont').scrollLeft % PageWidth); 
  CompScr(); 
 }else{ 
  MoveLock = false; 
 } 
 AutoPlay(); 
} 
function ISL_ScrUp(){ //上翻动作 
 if(GetObj('ISL_Cont').scrollLeft <= 0){GetObj('ISL_Cont').scrollLeft = GetObj('ISL_Cont').scrollLeft + GetObj('List1').offsetWidth} 
 GetObj('ISL_Cont').scrollLeft -= Space ; 
} 
function ISL_GoDown(){ //下翻 
 clearInterval(MoveTimeObj); 
 if(MoveLock) return; 
 clearInterval(AutoPlayObj); 
 MoveLock = true; 
 ISL_ScrDown(); 
 MoveTimeObj = setInterval('ISL_ScrDown()',Speed); 
} 
function ISL_StopDown(){ //下翻停止 
 clearInterval(MoveTimeObj); 
 if(GetObj('ISL_Cont').scrollLeft % PageWidth - fill != 0 ){ 
  Comp = PageWidth - GetObj('ISL_Cont').scrollLeft % PageWidth + fill; 
  CompScr(); 
 }else{ 
  MoveLock = false; 
 } 
 AutoPlay(); 
} 
function ISL_ScrDown(){ //下翻动作 
 if(GetObj('ISL_Cont').scrollLeft >= GetObj('List1').scrollWidth){GetObj('ISL_Cont').scrollLeft = GetObj('ISL_Cont').scrollLeft - GetObj('List1').scrollWidth;} 
 GetObj('ISL_Cont').scrollLeft += Space ; 
} 
function CompScr(){ 
 var num; 
 if(Comp == 0){MoveLock = false;return;} 
 if(Comp < 0){ //上翻 
  if(Comp < -Space){ 
   Comp += Space; 
   num = Space; 
  }else{ 
   num = -Comp; 
   Comp = 0; 
  } 
  GetObj('ISL_Cont').scrollLeft -= num; 
  setTimeout('CompScr()',Speed); 
 }else{ //下翻 
  if(Comp > Space){ 
   Comp -= Space; 
   num = Space; 
  }else{ 
   num = Comp; 
   Comp = 0; 
  } 
  GetObj('ISL_Cont').scrollLeft += num; 
  setTimeout('CompScr()',Speed); 
 } 
} 
//--><!]]>
</script>
<table width="483" height="106" border="0" align="center" cellpadding="0" cellspacing="0">
              <tr>
                <td width="31"><div class="RightBotton" onmousedown="ISL_GoDown()" onmouseup="ISL_StopDown()" onmouseout="ISL_StopDown()"></div></td>
                <td width="421" valign="top">
                <div class="rollBox"><div class="Cont" id="ISL_Cont"><div class="ScrCont"><div id="List1">
                            <asp:DataList ID="MyDatas" runat="server" BorderWidth="0px" CellPadding="0" GridLines="Both" RepeatDirection="Horizontal" RepeatColumns="100">
    <ItemTemplate>                <table width="118" height="105" border="0" cellspacing="0" cellpadding="0">
                  <tr>
                    <td valign="top"><table width="50" height="16" border="0" cellspacing="0" cellpadding="0">
                        <tr>
                          <td>&nbsp;</td>
                        </tr>
                      </table>
                        <table width="85" height="65" border="0" cellpadding="0" cellspacing="1" bgcolor="#cfcac0">
                          <tr>
                            <td align="center" bgcolor="#FFFFFF"><img src="images/a/cp.gif" width="83" height="63" /></td>
                          </tr>
                        </table>
                      <table width="85" height="22" border="0" cellspacing="0" cellpadding="0">
                          <tr>
                            <td align="center" valign="bottom" style="color:#77674a">如意聚宝盆</td>
                          </tr>
                      </table></td>
                  </tr>
                </table>
                  </ItemTemplate>
</asp:DataList></div><div id="List2"></div></div></div></div>                </td>
                <td width="31" align="right"><div class="LeftBotton" onmousedown="ISL_GoUp()" onmouseup="ISL_StopUp()" onmouseout="ISL_StopUp()"></div></td>
              </tr>
            </table>
 

Answer 1

把你的js脚本全部移到table的下面，你在获取List2的时候，页面还没加载！自然会取得null，应该如下：<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
 <HEAD>
  <TITLE> New Document </TITLE>
  <META NAME="Generator" CONTENT="EditPlus">
  <META NAME="Author" CONTENT="">
  <META NAME="Keywords" CONTENT="">
  <META NAME="Description" CONTENT="">
  <style type="text/css"> 
.rollBox{width:421px;overflow:hidden;padding:0;} 
.LeftBotton{height:106px;width:10px;background:url(images/a/y.gif) no-repeat 0 0;overflow:hidden;float:left;display:inline;margin:0 5px 0 5px;cursor:pointer;} 
.RightBotton{height:106px;width:10px;background:url(images/a/z.gif) no-repeat 0 0;overflow:hidden;float:left;display:inline;margin:0 0 0 0;cursor:pointer;} 
.rollBox .Cont{width:800px;overflow:hidden;float:left;} 
.rollBox .ScrCont{width:1000px;} 
.rollBox #List1,.rollBox #List2{float:left;} 
</style> 
 </HEAD> <BODY><table width="483" height="106" border="0" align="center" cellpadding="0" cellspacing="0"> 
              <tr> 
                <td width="31"> <div class="RightBotton" onmousedown="ISL_GoDown()" onmouseup="ISL_StopDown()" onmouseout="ISL_StopDown()"> </div> </td> 
                <td width="421" valign="top"> 
                <div class="rollBox"> <div class="Cont" id="ISL_Cont"> <div class="ScrCont"> <div id="List1"> 
                            <asp:DataList ID="MyDatas" runat="server" BorderWidth="0px" CellPadding="0" GridLines="Both" RepeatDirection="Horizontal" RepeatColumns="100"> 
    <ItemTemplate>                 <table width="118" height="105" border="0" cellspacing="0" cellpadding="0"> 
                  <tr> 
                    <td valign="top"> <table width="50" height="16" border="0" cellspacing="0" cellpadding="0"> 
                        <tr> 
                          <td>&nbsp; </td> 
                        </tr> 
                      </table> 
                        <table width="85" height="65" border="0" cellpadding="0" cellspacing="1" bgcolor="#cfcac0"> 
                          <tr> 
                            <td align="center" bgcolor="#FFFFFF"> <img src="images/a/cp.gif" width="83" height="63" /> </td> 
                          </tr> 
                        </table> 
                      <table width="85" height="22" border="0" cellspacing="0" cellpadding="0"> 
                          <tr> 
                            <td align="center" valign="bottom" style="color:#77674a">如意聚宝盆 </td> 
                          </tr> 
                      </table> </td> 
                  </tr> 
                </table> 
                  </ItemTemplate> 
</asp:DataList> </div> <div id="List2"> </div> </div> </div> </div>                 </td> 
                <td width="31" align="right"> <div class="LeftBotton" onmousedown="ISL_GoUp()" onmouseup="ISL_StopUp()" onmouseout="ISL_StopUp()"> </div> </td> 
              </tr> 
            </table> 
<script language="javascript" type="text/javascript"> 
<!--//--> <![CDATA[//> <!-- 
//图片滚动列表 mengjia 070816 
var Speed = 10; //速度(毫秒) 
var Space = 5; //每次移动(px) 
var PageWidth = 327; //翻页宽度 
var fill = 0; //整体移位 
var MoveLock = false; 
var MoveTimeObj; 
var Comp = 0; 
var AutoPlayObj = null; 
GetObj("List2").innerHTML = GetObj("List1").innerHTML; 
GetObj('ISL_Cont').scrollLeft = fill; 
GetObj("ISL_Cont").onmouseover = function(){clearInterval(AutoPlayObj);} 
GetObj("ISL_Cont").onmouseout = function(){AutoPlay();} 
AutoPlay(); 
function GetObj(objName){if(document.getElementById){return eval('document.getElementById("'+objName+'")')}else{return eval('document.all.'+objName)}} 
function AutoPlay(){ //自动滚动 
clearInterval(AutoPlayObj); 
AutoPlayObj = setInterval('ISL_GoDown();ISL_StopDown();',3000); //间隔时间 
} 
function ISL_GoUp(){ //上翻开始 
if(MoveLock) return; 
clearInterval(AutoPlayObj); 
MoveLock = true; 
MoveTimeObj = setInterval('ISL_ScrUp();',Speed); 
} 
function ISL_StopUp(){ //上翻停止 
clearInterval(MoveTimeObj); 
if(GetObj('ISL_Cont').scrollLeft % PageWidth - fill != 0){ 
  Comp = fill - (GetObj('ISL_Cont').scrollLeft % PageWidth); 
  CompScr(); 
}else{ 
  MoveLock = false; 
} 
AutoPlay(); 
} 
function ISL_ScrUp(){ //上翻动作 
if(GetObj('ISL_Cont').scrollLeft <= 0){GetObj('ISL_Cont').scrollLeft = GetObj('ISL_Cont').scrollLeft + GetObj('List1').offsetWidth} 
GetObj('ISL_Cont').scrollLeft -= Space ; 
} 
function ISL_GoDown(){ //下翻 
clearInterval(MoveTimeObj); 
if(MoveLock) return; 
clearInterval(AutoPlayObj); 
MoveLock = true; 
ISL_ScrDown(); 
MoveTimeObj = setInterval('ISL_ScrDown()',Speed); 
} 
function ISL_StopDown(){ //下翻停止 
clearInterval(MoveTimeObj); 
if(GetObj('ISL_Cont').scrollLeft % PageWidth - fill != 0 ){ 
  Comp = PageWidth - GetObj('ISL_Cont').scrollLeft % PageWidth + fill; 
  CompScr(); 
}else{ 
  MoveLock = false; 
} 
AutoPlay(); 
} 
function ISL_ScrDown(){ //下翻动作 
if(GetObj('ISL_Cont').scrollLeft >= GetObj('List1').scrollWidth){GetObj('ISL_Cont').scrollLeft = GetObj('ISL_Cont').scrollLeft - GetObj('List1').scrollWidth;} 
GetObj('ISL_Cont').scrollLeft += Space ; 
} 
function CompScr(){ 
var num; 
if(Comp == 0){MoveLock = false;return;} 
if(Comp < 0){ //上翻 
  if(Comp < -Space){ 
  Comp += Space; 
  num = Space; 
  }else{ 
  num = -Comp; 
  Comp = 0; 
  } 
  GetObj('ISL_Cont').scrollLeft -= num; 
  setTimeout('CompScr()',Speed); 
}else{ //下翻 
  if(Comp > Space){ 
  Comp -= Space; 
  num = Space; 
  }else{ 
  num = Comp; 
  Comp = 0; 
  } 
  GetObj('ISL_Cont').scrollLeft += num; 
  setTimeout('CompScr()',Speed); 
} 
} 
//--> <!]]> 
</script> 
 </BODY>
</HTML>