使用ajax数据绘制Chart.js并响应.一些问题和疑问

Question

我正在使用Chart.js(http://www.chartjs.org/docs/)进行制图.

我需要从Ajax请求中获取数据并使图表具有响应性.

在我的HTML代码中,我添加了一个画布,如下所示:

<div>
  <canvas id="userscreated" class="plot" data-url="/stats/userscreated"></canvas>
</div>

在我的javascript(JQuery)代码中,我有:

var data2;

$.ajax({
  url: $('#userscreated').data('url'),
  async: true,
  dataType: 'json',
  type: "get",
}).done(function (data) {

    data2 = data;

    // Draw chart
    var context = $('#userscreated').get(0).getContext("2d");
    var wrapper = $('#userscreated').parent();
    var width = $('#userscreated').attr('width', $(wrapper).width());

    new Chart(context).Line(
    {
      labels: data.Dates,
      datasets: [
        { fillColor: #404040, data: data.Users }
      ]
    },
    { animation: false }
  );

});

// Redraw the chart with the same data
$(window).resize(function () {

  var context = $('#userscreated').get(0).getContext("2d");
  var wrapper = $('#userscreated').parent();
  var width = $('#userscreated').attr('width', $(wrapper).width());

  new Chart(context).Line(
    {
      labels: data2.Dates,
      datasets: [
        { fillColor: #404040, data: data2.Users }
      ]
    },
    { animation: false }
  );

});

问题

1. 窗口调整大小时未调整图表大小.
2. 有没有更好的代码来做到这一点？我想我会重复很多代码.
3. 在谷歌,绘图很快.在firefox中有时会挂起一段时间.我的代码有什么问题吗？
4. 该请求应该是异步还是不同步？

Answer 1

您可以使异步AJAX调用没问题.只有在成功回调触发后才设置图表,这一点非常重要.否则,您将无法定义画布上下文的问题.第一次调用respondCanvas进行初始设置,而后续调用进行大小调整.

这对我有用:

var max = 0;
var steps = 10;
var chartData = {};

function respondCanvas() {
    var c = $('#summary');
    var ctx = c.get(0).getContext("2d");
    var container = c.parent();

    var $container = $(container);

    c.attr('width', $container.width()); //max width

    c.attr('height', $container.height()); //max height                   

    //Call a function to redraw other content (texts, images etc)
    var chart = new Chart(ctx).Line(chartData, {
        scaleOverride: true,
        scaleSteps: steps,
        scaleStepWidth: Math.ceil(max / steps),
        scaleStartValue: 0
    });
}

var GetChartData = function () {
    $.ajax({
        url: serviceUri,
        method: 'GET',
        dataType: 'json',
        success: function (d) {
           chartData = {
                labels: d.AxisLabels,
                datasets: [
                    {
                        fillColor: "rgba(220,220,220,0.5)",
                        strokeColor: "rgba(220,220,220,1)",
                        pointColor: "rgba(220,220,220,1)",
                        pointStrokeColor: "#fff",
                        data: d.DataSets[0]
                    }
                ]
            };

            max = Math.max.apply(Math, d.DataSets[0]);
            steps = 10;

            respondCanvas();
        }
    });
};

$(document).ready(function() {
    $(window).resize(respondCanvas);

    GetChartData();
});

如果要在调用之间插入一个小延迟,可以使用超时:

$(document).ready(function() {
    $(window).resize(setTimeout(respondCanvas, 500));

    GetChartData();
});

如果您的图表上有大型数据集,延迟将使您的调整大小更具响应性.

Answer 2

您可以在chart.js中进行设置

new Chart(context, {
  type:"line",
  labels: data.Dates,
  datasets: [
    { fillColor: #404040, data: data.Users }
  ]
  options: { responsive: false }
});

Answer 3

1. 的确
2. 是的，我给你举个例子。
3. 我没有看到任何可能引起问题的东西。除了 window.resize 可能会比您想要的更频繁地渲染新图表。
4. 没有。（我真的不知道为什么，这更像是巧合。）

代码：

window.getVisitCounts = ($canvas) ->
    url = Routes.visits_between_project_path($canvas.data('project-id'), {
        format: "json",
        start: $canvas.data('start'),
        end: $canvas.data('end')
    })


visits = []
days = []

 $.ajax
 url: url,
 async: false,
 dataType: "json",
 type: "GET",
 success: (data) - >
 for point in data.chart.data
 visits.push(point.visits)
 days.push(point.date)

 {
     days: days,
     visits: visits
 }

 window.createChartData = (raw) - > {
     labels: raw.days,
     datasets: [{
         fillColor: "rgba(151,187,205,0.5)",
         strokeColor: "rgba(151,187,205,1)",
         pointColor: "rgba(151,187,205,1)",
         pointStrokeColor: "#fff",
         data: raw.visits,
     }]
 }

 window.setupCanvas = ($canvas, data) - >
     newWidth = $canvas.parent().width()

 $canvas.prop
 width: newWidth
 height: 400

 options = {
     scaleOverride: true,
     scaleSteps: 10,
     scaleStepWidth: Math.ceil(Math.max.apply(Math, data.datasets[0].data) / 10),
     scaleStartValue: 0
 }

 ctx = $canvas.get(0).getContext("2d")
 new Chart(ctx).Line(data, options)

 $ - > @canvas = $("#analytics-canvas")
 if@ canvas.length != 0@ visits = window.createChartData(window.getVisitCounts(@canvas))
 window.setupCanvas(@canvas, @visits)

 $(window).on('resizeEnd', - >
     setupCanvas(document.canvas, document.visits)
 )

 $(window).resize - >
 if (@resizeTO)
     clearTimeout(@resizeTO)

 @resizeTO = setTimeout(- >
     $(this).trigger "resizeEnd"
     500
 )