怎样实现选单连动？？？？？？

Question

是在JSP的网页中吗？好像没法直接实现，除非你在选择第一个下拉框的值后再处发一个提交事件（如一个提交按钮），然后刷新当前页面，从而将从数据库中读取的内容赋到2个下样框中去!

Answer 1

是在jsp页面阿！！不能实现吗？？？？？

Answer 2

http://www.fason.nease.net/samples/bigarea/

Answer 3

先从数据库中把所有数据读出.定义一个二维数组用来保存数据.
<tr bgcolor="#FFFFFF"> 
        <td height="30"> <div align="left">
          <select name="searchC1" onChange="redirect(this.options.selectedIndex)" >
            <option  value="$"> ——请选择——</option>
            <option value="1">餐饮</option>
            <option value="2">零售业</option>
            <option value="4">汽车</option>
            <option value="5">住宿</option>
            <option value="6">休闲</option>
            <option value="7">公共设施</option>
            <option value="8">交通设施</option>
            <option value="9">文化、媒体</option>
            <option value="A">其他</option>
          </select>
        </div></td>
       </tr>
       <tr bgcolor="#FFFFFF"> 
            <td height="27"> <div align="left
                <select name="searchC2">
                  <option value="$">——请选择——</option>
                </select>
              </div></td>
          </tr><script language="JavaScript">
var tmp1=document.roundForm.searchC2;
function redirect(x)
{
   for (j=document.roundForm.searchC2.options.length-1;j>0;j--)
      tmp1.options[j]=null;     
   for (k=0;k<array1[x].length;k++)
     {
       tmp1.options[k]=new Option(array1[x][k].text,array1[x][k].value);
      }
   tmp1.options[0].selected=true;
}
</script>

Answer 4

代码比较复杂。
这是一个已经写成标签的下拉联动。
***********************************************************
package com.kmcrmsoft.business.taglib;import javax.servlet.jsp.tagext.TagSupport;
import javax.servlet.jsp.JspException;
import org.apache.struts.util.ResponseUtils;
import com.kmcrmsoft.database.DBManager;
import com.kmcrmsoft.database.DBResultSet;public class Option extends TagSupport {
    private DBManager db = new DBManager();    public void setDbmanager(DBManager dbmanager) {
        this.db = dbmanager;
    }    public DBManager getDbmanager() {
        return db;
    }    private String valuefield = "ID";
    public String getValuefield() {
        return valuefield;
    }    public void setValuefield(String valuefield) {
        this.valuefield = valuefield;
    }    private String selectedoption = null;
    public String getSelectedoption() {
        return valuefield;
    }    public void setSelectedvalue(String selectedoption) {
        this.selectedoption = selectedoption;
    }    private String textfield = "name";
    public String getTextfield() {
        return textfield;
    }    public void setTextfield(String textfield) {
        this.textfield = textfield;
    }    private String textfield_ex = null;
    public String getTextfield_ex() {
        return textfield_ex;
    }    public void setTextfield_ex(String textfield_ex) {
        this.textfield_ex = textfield_ex;
    }    private String tablename = "dual";
    public String getTablename() {
        return tablename;
    }    public void setTablename(String tablename) {
        this.tablename = tablename;
    }    private String where = null;
    public String getWhere() {
        return where;
    }    public void setWhere(String where) {
        this.where = where;
    }    public String getP_id_field() {
        return p_id_field;
    }    public void setP_id_field(String p_id_fieldValue) {
        this.p_id_field = p_id_fieldValue;
    }    public String getP_table_name() {
        return p_table_name;
    }    public void setP_table_name(String p_table_nameValue) {
        this.p_table_name = p_table_nameValue;
    }    public void setVar_perfix(String var_perfixValue) {
        this.var_perfix = var_perfixValue;
    }    public String getVar_perfix() {
        return var_perfix;
    }    public void setSub_function_name(String function_nameValue) {
        this.sub_function_name = function_nameValue;
    }    public String getSub_function_name() {
        return sub_function_name;
    }    public void setFather_function_name(String father_function_nameValue) {
        this.father_function_name = father_function_nameValue;
    }    public String getFather_function_name() {
        return father_function_name;
    }    public void setExt_field_name(String[] ext_field_nameValue) {
        this.ext_field_name = ext_field_nameValue;
    }    public String[] getExt_field_name() {
        return ext_field_name;
    }    public void setControl_name(String[] control_nameValue) {
        this.control_name = control_nameValue;
    }    public String[] getControl_name() {
        return control_name;
    }    public void setP_object_name(String p_object_nameValue) {
        this.p_object_name = p_object_nameValue;
    }    public String getP_object_name() {
        return p_object_name;
    }    public void setSub_object_name(String sub_object_nameValue) {
        this.sub_object_name = sub_object_nameValue;
    }    public String getSub_object_name() {
        return sub_object_name;
    }    public void setSet_val_function_name(String set_val_function_nameValue) {
        this.set_val_function_name = set_val_function_nameValue;
    }    public String getSet_val_function_name() {
        return set_val_function_name;
    }    public void setExt_perfix(String[] ext_perfixValue) {
        this.ext_perfix = ext_perfixValue;
    }    public String[] getExt_perfix() {
        return ext_perfix;
    }    public void setAdd_all(boolean add_allValue) {
        this.add_all = add_allValue;
    }    private String[] control_name; //要被賦值的控件名称
    private String[] ext_field_name; //要给控件付值的字段名称 control_name与control_name的长度必须相同
    private String[] ext_perfix; //用于选择控件的数组变量前缀    private String p_id_field = null ; //
    private String p_table_name = null; //
    private String var_perfix = ""; //数组变量前缀
    private String sub_function_name = "selectSubItem"; //函数名称
    private String father_function_name = "selectFatherItem"; //函数名称
    private String sub_object_name = null; //被选择的控件名
    private String p_object_name = null; //父的控件名
    private String set_val_function_name = "setVal"; //给控件赋值的函数名称
    private boolean add_all = false; //如果希望在selectSubItem中增加"全部"option,那就将此值设为true

Answer 5

public int doStartTag() throws JspException {
        String strSql = "";
        String strOutput = "\n";
        String strIsSelected = "";
        String strTempID = null;
        if (sub_object_name == null || sub_object_name.length() <= 0)
            sub_object_name = valuefield;
        if (p_object_name == null || p_object_name.length() <= 0)
            p_object_name = p_id_field;
            //组织sql语句
        strSql = "select " + valuefield + "," + textfield+","+p_id_field;
        if (ext_field_name != null && ext_field_name.length > 0) {
            for (int index = 0; index < ext_field_name.length; index++) {
                strSql = strSql + "," + ext_field_name[index];
            }
        }
        /*以下 行代码只适合oracle数据库 看表中是否有“DELETED”字段**********/
        DBManager dbC = new DBManager();
        String sql = "select count(*) c from col  where TNAME='" +
            tablename.toUpperCase() + "' and CNAME='DELETED'";
        DBResultSet rsC = dbC.Query(sql);
        String strDel = "";
        if (rsC.getInt("c") > 0) {
            strDel = " and deleted<>1 ";
        }
        rsC.close();
        /****************************************************************/        strSql = strSql + " from " +
            tablename +
            " where 1=1 " + strDel + (where == null ? "" : " and " + where);
        /*按照名称排序*/
        strSql = strSql +
            (where == null || where.indexOf("order by") < 0 ?
             " order by " + textfield : "");
        DBResultSet rs = db.Query(strSql);        String strContrl="";
        String strSelect="";
        int i = 0;
        int i2=0;
        rs.beforeFirst();
        String strTempName="";
        while (rs.next()) {
            //生成option标签
            strTempID = rs.getString(1);
            strIsSelected = " ";
            if((!strTempName.equals(rs.getString(2)))){//如果重名就不显示了                if (strTempID.equals(selectedoption))
                    strIsSelected = " selected ";
                strOutput = strOutput + "<option value=\"" + rs.getString(1) +
                    "\" " +
                    strIsSelected + ">" + rs.getString(2) + "</option> \n";
            }
            strTempName=rs.getString(2);
            //生成更改控件内容的数组
            if (control_name != null) {
                strContrl = strContrl + "    " + var_perfix + "_array[" +
                    i + "]=\"" +
                    rs.getString(1) +
                    "\"; \n";
                for (int index = 0; index < ext_field_name.length; index++) { //为每个扩展字段生成数组
                    strContrl = strContrl +
                        "    " +
                        (ext_perfix == null ? ext_field_name[index] :
                         ext_perfix[index]) + "_array[" + i +
                        "] =\"" + rs.getString(ext_field_name[index]) +
                        "\";\n";
                }
                i++;
            }
            //生成下拉选择的数组
            if (p_id_field != null && p_id_field.length() > 0) {
                strSelect = strSelect + "    " + var_perfix + "_tag_p_code[" +
                    i2 + "]=\"" +
                    rs.getString(3) +
                    "\"; " +
                    "    " + var_perfix + "_tag_item_id[" + i2 + "] =\"" +
                    rs.getString(1) + "\";\n" +
                    "    " + var_perfix + "_tag_item_name[" + i2 + "] =\"" +
                    rs.getString(2) + "\";\n";
                i2++;
            }
        }
        if (control_name != null) {
            strOutput = strOutput
                + "<script>\n"
                + "    //这个script中的代码是根据下拉框选择的值来更改指定控件的内容 的\n"
                + "    var " + var_perfix + "_array = new Array();\n";
            for (int index = 0; index < ext_field_name.length; index++) { //为每个扩展字段生成数组
                strOutput = strOutput
                    + "    var " +
                    (ext_perfix == null ? ext_field_name[index] :
                     ext_perfix[index]) +
                    "_array = new Array();\n";
            }
            strOutput+=strContrl;

Answer 6

strOutput = strOutput
                + "    function " + set_val_function_name + "(id) {\n"
                + "      for (jj = 0; jj < " + i + "; jj++) {\n"
                + "            if (" + var_perfix +
                "_array[jj] == id) {\n";            for (int index = 0; index < ext_field_name.length; index++) {
                strOutput = strOutput
                    +
                    "                document.all." + control_name[index] +
                    ".value=" +
                    (ext_perfix == null ? ext_field_name[index] :
                     ext_perfix[index]) + "_array[jj];\n";
            }
            strOutput = strOutput
                + "jj=" + i
                + "                }\n"
                + "        }\n"
                + "    }\n";            strOutput = strOutput + "</script>\n";        }        //如果有子项目
        if (p_id_field != null && p_id_field.length() > 0) {
            strOutput = strOutput
                + "<script>\n"
                + "    //这个script中的代码是选择子项目用的\n"
                + "    var " + var_perfix + "_tag_p_code = new Array();\n"
                + "    var " + var_perfix + "_tag_item_id = new Array();\n"
                + "    var " + var_perfix + "_tag_item_name = new Array();\n";            strOutput+=strSelect;            strOutput = strOutput
                + "    function " + father_function_name + "(id) {\n"
                + "        for (y = 0; y < " + i2 + ";y++){\n"
                + "            if(" + var_perfix + "_tag_item_id[y]==id){\n"
                + "                p_id_val=" + var_perfix +
                "_tag_p_code[y];\n"
                + "                y=" + i2 + "\n"
                + "            }"
                + "        }\n"
                + "        for (w = 0; w < document.all." + p_object_name +
                ".options.length;w++){\n"
                + "            if (document.all." + p_object_name +
                ".options[w].value == p_id_val) {\n"
                + "                document.all." + p_object_name +
                ".options[w].selected=true;\n"
                + "                w=document.all." + p_object_name +
                ".options.length;\n"
                + "            }"
                + "        }\n"
                + "    }\n"
                //+ "    selectSubItem(document.all." + p_id_field +".value);//选择子项\n"
                + "    function " + sub_function_name + "(id) {\n"
                +
                "        for (k = 0; k < document.all." + sub_object_name +
                ".options.length;)\n"
                + "            document.all." + sub_object_name +
                ".remove(0);\n";
            /*如果要增加一个“全部”的option*/
            if (add_all) {
                strOutput = strOutput
                    + "        var objOption = new Option(\"全部\",\"-1\");\n"
                    +
                    "                document.all." + sub_object_name +
                    ".add(objOption);\n";
            }
            strOutput = strOutput
                + "      for (j = 0; j < " + i2 + "; j++) {\n"
                + "            if (id==-1||" + var_perfix +
                "_tag_p_code[j] == id) {\n"
                +
                "                var objOption = new Option(" + var_perfix +
                "_tag_item_name[j], " + var_perfix + "_tag_item_id[j]);\n"
                +
                "                document.all." + sub_object_name +
                ".add(objOption);\n"
                + "                }\n"
                + "        }\n"
                + "        if(document.all." + sub_object_name +
                ".options.length>0)document.all." + sub_object_name +
                ".options[0].selected=true;\n"
                + "    }\n"
                + "</script>\n";        }
        rs.close();
        ResponseUtils.write(pageContext, strOutput);        return (EVAL_BODY_INCLUDE);
    }
}

Answer 7

其实原理就是先从数据库中把
两个下拉筐所需要的数据都从数据库中读取出来。
有value / name 还有就是他们之间关联的值。比如当select1中选中了value=7的
那么，select2先删除所有的数据然后再添加 xx字段=7 的所有数据。
这些功能都是通过javascript实现的。

Answer 8

谢谢  zhonghua2003(爱我中华)，你的方法感觉应该可行。。也感谢 yunxiang(*****) 代码有些看不懂，不过我相信可以实现。。