Chart.js 错误无法读取 null 的属性“长度”

Question

我正在通过 ajax 调用使用

Chart.js

         $.ajax({
         url: 'MenuG.aspx/GetGraphData',
         type: "POST",
         data: "{}",
         dataType: "json",
         contentType: "application/json; charset=utf-8",
         success: loadChart,
         error: function (xhr, status, error) {
             alert("קרתה שגיאה בטעינת הגרף");
         }
     });

 function loadChart(jsonData) {

     var data = jsonData.d;
     if (data != undefined && data != null) {
         if (data.Col1 != null && data.Col2 != null && data.Col3 != null && data.Col4 != null) {
             var labelsToDisplay = [data.Col1.Desc, data.Col2.Desc, data.Col3.Desc, data.Col4.Desc];
             var dataTotal = [parseInt(data.Col1.total), parseInt(data.Col2.total), parseInt(data.Col3.total), parseInt(data.Col4.total)];

             new Chart(document.getElementById("bar-chart"), {
                 type: 'bar',
                 data: {
                     labels: labelsToDisplay,
                     datasets: [
                {
                    //label: "Population (millions)",
                    backgroundColor: ["#3e95cd", "#8e5ea2", "#3cba9f", "#e8c3b9"],
                    data: dataTotal
                }
              ]
                 },
                 options: {
                     legend: { display: false },
                     title: {
                         display: true,
                         text: jsonData.GraphName
                     },
                     animation: { // show each column total on top
                         onComplete: function () {
                             var ctx = this.chart.ctx;
                             ctx.font = Chart.helpers.fontString(Chart.defaults.global.defaultFontFamily, 'normal', Chart.defaults.global.defaultFontFamily);
                             ctx.fillStyle = "black";
                             ctx.textAlign = 'center';
                             ctx.textBaseline = 'bottom';

                             this.data.datasets.forEach(function (dataset) {
                                 for (var i = 0; i < dataset.data.length; i++) {
                                     for (var key in dataset._meta) {
                                         var model = dataset._meta[key].data[i]._model;
                                         ctx.fillText(dataset.data[i], model.x, model.y - 5);
                                     }
                                 }
                             });
                         }
                     }
                 }
             }); //Chart
         }//if
     }// if
 } //loadChart

我创建了 2 个数组

labelsToDisplay

用于条形标签，

dataTotal

用于条形值（我检查过，它们都有 4 个值）。

但是，我得到：-

未捕获类型错误：无法读取 null 的属性“长度”

Uncaught TypeError: Cannot read property 'length' of null
at Object.acquireContext (Chart.min.js:13)
at t.construct (Chart.min.js:11)
at new t (Chart.min.js:12)
at Object.loadChart [as success] (MenuG.aspx?param=1:66)
at j (jquery.js:3148)
at Object.fireWith [as resolveWith] (jquery.js:3260)
at x (jquery.js:9314)
at XMLHttpRequest.b (jquery.js:9718)

Answer 1

我正在使用 Chart.js 库的 CDN，当下载该库并将其放入我的项目时，它以某种方式解决了问题......