jQuery EasyUI中的tree使用指南

　　本文记录的是带领成员开发一个小模块功能的时候，需要用到弹出窗口加载树状级联单位选择，最后决定用采用jquery+easyui插件进行开发。但是在使用easyui中tree的插件时，碰到了不少麻烦。为了提供弹出树的显示速度，就采用异步加载数节点值，首先先加载根节点，然后根据点击的节点展开加载子节点。

　　往往结果和预期的都不一样，困惑了几天，展开后子节点是动态加载了，但是收缩后无法清空之前填充的数据；第二次在展开时，子节点又被重复加载了一遍，造成了数据重复显示，并没有提供清除子节点的方法。想尽了各种办法来解决这个问题，只能换另一种形式加载子节点的值了，把每一个节点值保存起来，判断是否已经存在，存在就不在去加载。

　　两种方法见实例：

 

代码如下:

var treetitle = '选择列表';
var treeurl = '../dataashx/gettreenode.ashx?pid=-1';
var nodeexp=false;
var nodekeep="";
var rows;
var noinf=0;
$(function() {
    $('#treewindow').window({
        title: treetitle,
        width: 400,
        height: 400,
        modal: true,
        shadow: false,
        closed: true,
        resizable: false,
        maximizable: false,
        minimizable: false,
        collapsible: false
    });
});
function treewindowopen(name,rowindx) {
    $('#treewindow').window('open');
    nodekeep="";
    nodeexp=false;
    rows=rowindx.tostring();
    $('#basetree').tree({
        checkbox: true,
        animate: true,
        url: treeurl+"&coln="+escape(name.tostring()),
        cascadecheck: true,
        onlyleafcheck: false,
        onbeforeexpand: function(node, param) {
//------------第一种方法：异步加载子节点值-------------
//            $('#basetree').tree('options').url = "../dataashx/gettreenode.ashx?pid=" + node.id+"&coln="+escape(name.tostring());
//------------第二种方法：ajax方法返回子节点json值，使用append方法加载子节点      
        $.ajax({
                type: "post",
                url: "../dataashx/gettreenode.ashx?pid=" + node.id+"&coln="+escape(name.tostring())+"&casn="+escape(node.attributes.cas.tostring()),
                cache: false,
                async: false,
                datatype: "json",
                success: function(data) {
                    if(nodekeep.indexof(node.id)==-1)
                    {
                     append(data, node);
                     nodeexp = true;
                    }
                }
            });
            $("#radcollapse").removeattr("checked");
        },
        onloaderror:function(error)
        {
            $.messager.alert('提示', '查询语句出错', 'error');
            if(nodeexp==false)
            {
                $("#basetree").children().remove();
            }
        },
        onloadsuccess:function(success)
        {
            var child=$("#basetree").children().length;
            noinf++;
            if(child==0&&noinf>1)
            {
                $.messager.alert('提示', '数据不存在', 'info');
            }
        }
    });
}
function treewindowclose() {
    $('#treewindow').window('close');
    nodekeep="";
    nodekeep=false;
}
function treewindowsubmit() {
    var nodes = $('#basetree').tree('getchecked');
    var info = '';
    if (nodes.length > 0) {
        for (var i = 0; i < nodes.length; i++) {
            if (info != '') { info += ','; }
            info += nodes[i].text;
        }
        //alert(json.stringify(nodes));
    }
    else {
        var node = $('#basetree').tree('getselected');
        if (node != null) {
            info = node.text;               
        }
    }
    $("#"+rows).val(info);
    $('#treewindow').window('close');
    nodekeep="";
    nodeexp=false;
}
//全部展开
function collapseall() {
    $("#radcollapse").attr("checked", "checked");
    var node = $('#basetree').tree('getselected');
    if (node) {
        $('#basetree').tree('collapseall', node.target);
    } else {
        $('#basetree').tree('collapseall');
    }
}
//全部收缩
function expandall() {
    var node = $('#basetree').tree('getselected');
    if (node) {
        $('#basetree').tree('expandall', node.target);
    } else {
        $('#basetree').tree('expandall');
    }
}
//增加子节点
function append(datas,cnode) {
    var node = cnode;
    $('#basetree').tree('append', {
        parent: node.target,
        data: datas
    });
    nodekeep+=","+node.id;
}
//重新加载
function reload() {
    var node = $('#basetree').tree('getselected');
    if (node) {
        $('#basetree').tree('reload', node.target);
    } else {
        $('#basetree').tree('reload');
    }
}
//删除子节点
function remove() {
    var node = $('#basetree').tree('getselected');
    $('#basetree').tree('remove',node.target);
}

 

　　页面gettreenode.ashx返回树节点json格式数据：

 

代码如下:

<%@ webhandler language="c#" class="gettreenode" %>
using system;
using system.collections;
using system.data;
using system.linq;
using system.web;
using system.web.services;
using system.web.services.protocols;
using system.xml.linq;
using system.collections.generic;

 

public class gettreenode : ihttphandler, system.web.sessionstate.irequiressessionstate
{
    public void processrequest(httpcontext context)
    {
        context.response.contenttype = "text/plain";
        datatable dt = (datatable)context.session["viewmaintain"];
        string parentid = string.empty;
        string resultstr = string.empty;
        string attributes = string.empty;
        string colname = string.empty;
        string sql = string.empty;
        string casname = string.empty;
        bool colt = false;
        string icon = "icon-profile";
        if (!string.isnullorempty(context.request.querystring["pid"]))
        {
            parentid = context.request.querystring["pid"].tostring();
        }
        if ((!string.isnullorempty(context.request.querystring["coln"])) && (string.isnullorempty(context.request.querystring["casn"])))
        {
            colname = httputility.urldecode(context.request.querystring["coln"].tostring());
            if (dt != null)
            {
                bool pt = true;
                while (pt)
                {
                    for (int i = 0; i < dt.rows.count; i++)
                    {
                        casname = dt.rows[i]["view_colname"].tostring();
                        if (dt.rows[i]["view_colname"].tostring() == colname)
                        {
                            if (dt.rows[i]["view_cas"].tostring() != null&&dt.rows[i]["view_cas"].tostring() !="")
                            {
                                colname = dt.rows[i]["view_cas"].tostring();
                            }
                            else
                            {
                                colt = true;
                                sql = dt.rows[i]["view_sql"].tostring();
                                pt = false;
                            }
                            break;
                        }
                    }
                }
            }
        }
        if ((!string.isnullorempty(context.request.querystring["casn"])) && (!string.isnullorempty(context.request.querystring["coln"])))
        {
           string casnname = httputility.urldecode(context.request.querystring["casn"].tostring());
           colname = httputility.urldecode(context.request.querystring["coln"].tostring());
            if (dt != null)
            {
                for (int i = 0; i < dt.rows.count; i++)
                {
                    casname = dt.rows[i]["view_colname"].tostring();
                    if (dt.rows[i]["view_cas"].tostring() == casnname && casnname != colname)
                    {
                        colt = true;
                        sql = dt.rows[i]["view_sql"].tostring();
                        break;
                    }
                }
            }
        }
        try
        {
            if (parentid != "" && colt == true)
            {
                //此处省略得到数据列表的代码
                list<treeinfo> ltree = dal_treeinfo.getitemvalue(parentid, sql);
                resultstr = "";
                resultstr += "[";
                if (ltree.count > 0)
                {
                    foreach (treeinfo item in ltree)
                    {
                        attributes = "";
                        attributes += "{\"cas\":\"" + casname;
                        attributes += "\",\"val\":\"" + item._text + "\"}";
                        resultstr += "{";
                        resultstr += string.format("\"id\": \"{0}\", \"text\": \"{1}\", \"iconcls\": \"{2}\", \"attributes\": {3}, \"state\": \"closed\"", item._id, item._text, icon, attributes);
                        resultstr += "},";
                    }
                    resultstr = resultstr.substring(0, resultstr.length - 1);
                }
                resultstr += "]";
            }
            else
            {
                resultstr = "[]";
            }
        }
        catch (exception ex)
        {
            resultstr = "出错";
        }
        context.response.write(resultstr);
    }
    public bool isreusable
    {
        get
        {
            return false;
        }
    }
}

 
　　关键性的代码都已经在上面了，目前也就只能想到这种办法来解决了，有时间的话可以给tree扩展一下，添加一个清除子节点的方法，这样应该实现起来会更容易方便。