Jqgrid子网格json数据未显示

主网格加载数据很好，但不显示子网格数据。

这是我的java控制器为子网格返回的json数据：

｛"allTrackingNrs"：null，"page"：1，"记录"：[｛"reference"："DGL1008"，"shipUnitType"："CARTON"，"totalOfCartons"：1，"trackingNr"："SLC160759060"："DGL1008"，"shipUnitType"："CARTON"，"totalOfCartons"：1，"trackingNr"："SLC160759060"｝]，"recordsTotal"：4，"rows"：4、"sidx"：null、"sord"："asc"、"total"：1、"trackingNr"："SLC160759060"、"truckId"：null，"truckShipmentComponent"：｛｝｝

这是我的javascript代码

<script type="text/javascript">
    jQuery().ready(function () {
        var grid = jQuery("#shipment_grid");
        var mainGridPrefix = "s_";
        grid.jqGrid({
            url: '${pageContext.request.contextPath}/getTruckShipmentJSONAction?truckId=' + <c:out value="${truckId}" />,
            datatype: "json",
            mtype: 'GET',
            colNames: ['Lead Tracking #'],
            colModel: [
                {name: 'trackingNr', width: 100}
            ],
            rowNum: 10,
            height: "auto",
            width: 850,
            idPrefix: mainGridPrefix,
            autoheight: true,
            rowList: [10, 20, 30],
            pager: jQuery('#shipment_grid_pager'),
            sortname: 'trackingNr',
            emptyrecords: 'No shipments found with the selected filter(s)',
            sortorder: "desc",
            jsonReader: {
                root: "records",
                page: "page",
                total: "total",
                records: "rows",
                repeatitems: false
            },
            viewrecords: true,
            altRows: false,
            gridview: true,
            multiselect:true,
            hidegrid: false,
            shrinkToFit: true,
            forceFit: true,
            idPrefix: mainGridPrefix,
            caption: "Shipments Overview",
            subGrid: true,
            loadComplete: function(data) {
                grid.jqGrid('setColProp', 'trackingNr',{
                    searchoptions: {
                        clearSearch: true,
                        attr: {style: "align:'left'; width:150px;margin-top:1px;"},
                        sopt:['cn'],
                        dataInit: function(elem) {
                            $(elem).autocomplete({
                                source:data.allTrackingNrs,
                                delay:0,
                                minLength:2
                            });
                        }
                    }
                });
                grid.jqGrid('filterToolbar', {autoSearch: true});
                // reduce font size of autocomplete input
                $(".ui-autocomplete.ui-widget").css({fontSize: "11px"});
            },
            subGridRowExpanded: function (subgridDivId, rowId) {
                var rowData = grid.getRowData(rowId);
                var selTrackingNr= rowData['trackingNr'];
                var $subgrid = $("<table id='" + subgridDivId + "_t'></table>");
                   //     pureRowId = $.jgrid.stripPref(mainGridPrefix, rowId),
                    //    subgrids = $(this).jqGrid("getGridParam", "userData");
                $subgrid.appendTo("#" + $.jgrid.jqID(subgridDivId));
                $subgrid.jqGrid({
                    data: "json",
                    mtype: 'GET',
                    url: '${pageContext.request.contextPath}/getTruckShipmentJSONAction?trackingNr=' + selTrackingNr,
                    colNames: ['Ship Type (Pallet / Carton)', 'Ship Unit (Pallet ID / Cone #)', 'Total Cartons'],
                    colModel: [
                        { name: "shipUnitType"},
                        { name: "reference", sorttype: "integer" },
                        { name: "totalOfCartons", sorttype: "integer" }
                    ],
                    cmTemplate: { align: "center" },
                    jsonReader: {
                        root: "records",
                        repeatitems: false
                    },
                    sortname: "reference",
                    sortorder: "desc",
                    height: "100%",
                    rowNum: 10,
                    autowidth: true,
                    autoencode: true,
                    gridview: true,
                    idPrefix: rowId + "_"
                });
            }
        }).navGrid('#shipment_grid_pager', {edit: false, add: false, del: false, search: false, refresh: true})
                .jqGrid("setLabel", "trackingNr", "", {"text-align": "left"}); //align 'Lead Tracking #' column header  to the left;

    });
</script>

如何显示子网格数据？