extjs 说不是构造函数 大神来帮忙看看

 var grid_gxcw = Ext.define('grid_widget_gxcw',{
    extend:'Ext.grid.Panel',
    alias:'widget.gridgxcw',
    initComponent:function(){
        Ext.apply(this,{
            store: store_GXCW,
            id: 'gridGXCW',
            columnLines: true,
            layout: 'fit',
            viewConfig: {forceFit: true},
            columns: [
                {
                    text: '线路名称', dataIndex: 'XLMC', flex: 1, renderer: function (value) {
                    if (value) {
                        return value;
                    } else return '-';
                }
                },
                {
                    text: '安装地址', dataIndex: 'ADDRESS', flex: 1, renderer: function (value) {
                    if (value) {
                        return value;
                    } else return '-';
                }
                },
                {
                    text: '最高温(℃)', dataIndex: 'B_MAX_VALUE', flex: 1, renderer: function (value) {
                    if (value) {
                        return value;
                    } else return '-';
                }
                },
                {
                    text: '当前时间', dataIndex: 'B_CUR_TIME', flex: 1, renderer: function (value) {
                    if (value) {
                        return value;
                    } else return '-';
                }
                },

                {
                    text: '运行编号', dataIndex: 'YXBH', flex: 1, renderer: function (value) {
                    if (value) {
                        return value;
                    } else return '-';
                }
                },
                {
                    text: '备注', dataIndex: 'REMARK', flex: 1, renderer: function (value) {
                    if (value) {
                        return value;
                    } else return '-';
                }
                }
            ]
        });
        this.callParent(arguments);
    },
    listeners: {
        'itemcontextmenu': itemcontextmenu
    }
});

注意作用域，你的grid_gxcw变量要在itemcontextmenu范围内才能访问到，grid_gxcw肯定是超出itemcontextmenu函数的访问范围了