向Chart.js折线图添加标题

Question

我尝试使用fillText在渲染后的chart.js画布上绘制，但无法成功。我所能做的最好的就是更改图表的字体。以下是我的代码。

var options = {

    //Boolean - If we show the scale above the chart data           
    scaleOverlay: false,

    //Boolean - If we want to override with a hard coded scale
    scaleOverride: false,

    //** Required if scaleOverride is true **
    //Number - The number of steps in a hard coded scale
    scaleSteps: null,
    //Number - The value jump in the hard coded scale
    scaleStepWidth: null,
    //Number - The scale starting value
    scaleStartValue: null,

    //String - Colour of the scale line 
    scaleLineColor: "rgba(0,0,0,.1)",

    //Number - Pixel width of the scale line    
    scaleLineWidth: 1,

    //Boolean - Whether to show labels on the scale 
    scaleShowLabels: true,

    //Interpolated JS string - can access value
    scaleLabel: "<%=value%>",

    //String - Scale label font declaration for the scale label
    scaleFontFamily: "'Arial'",

    //Number - Scale label font size in pixels  
    scaleFontSize: 12,

    //String - Scale label font weight style    
    scaleFontStyle: "normal",

    //String - Scale label font colour  
    scaleFontColor: "#666",

    ///Boolean - Whether grid lines are shown across the chart
    scaleShowGridLines: true,

    //String - Colour of the grid lines
    scaleGridLineColor: "rgba(0,0,0,.05)",

    //Number - Width of the grid lines
    scaleGridLineWidth: 1,

    //Boolean - Whether the line is curved between points
    bezierCurve: true,

    //Boolean - Whether to show a dot for each point
    pointDot: true,

    //Number - Radius of each point dot in pixels
    pointDotRadius: 3,

    //Number - Pixel width of point dot stroke
    pointDotStrokeWidth: 1,

    //Boolean - Whether to show a stroke for datasets
    datasetStroke: true,

    //Number - Pixel width of dataset stroke
    datasetStrokeWidth: 2,

    //Boolean - Whether to fill the dataset with a colour
    datasetFill: true,

    //Boolean - Whether to animate the chart
    animation: false,

    //Number - Number of animation steps
    animationSteps: 60,

    //String - Animation easing effect
    animationEasing: "easeOutQuart",

    //Function - Fires when the animation is complete
    onAnimationComplete: null

}

图表数据标签和点是数组。

                   var chartData = {
                        labels: labels,
                        datasets: [
                            {
                                fillColor: "rgba(220,220,220,0.5)",
                                strokeColor: "rgba(220,220,220,1)",
                                pointColor: "rgba(220,220,220,1)",
                                pointStrokeColor: "#fff",
                                data: points
                            }
                        ]
                    }

                    var ctx = $("#" + item.logon).get(0).getContext("2d");
                    var chart = new Chart(ctx).Line(chartData, options);

这是通过JSON数据完成的，在调用后，我有：

                $("canvas").each(function (i, item) {
                    var context = $(this).get(0).getContext("2d");
                    context.textBaseline = 'top';
                    context.fillText('Test', 0, 0);
                });

这些图表加载时没有显示任何文本。如果我使用 context.font，则会更改每个画布上的所有标签。我已经关闭了加载动画。有什么想法吗？

- Todd Skelton

Answer 1

我不是在画布上绘制，而是在元素周围添加标签

<label for = "idOfCanvas">
Your Label<br />
    <canvas></canvas>
</label>

- 9Deuce

---

是的，这就是我一直在做的。我真的很喜欢能够将图表转换为图像并保存它们。唯一的问题是，除非我在画布上绘制，否则没有标签。 - Todd Skelton

@ToddSkelton 我认为修改代码让标签自动绘制是可行的，不应该是不可能的。 - 9Deuce

Answer 2

您需要在选项部分添加具体的标题，并确保显示设置为true。类似于以下内容：

options: {
    title: {
        display: true,
        text: 'Name of Your Line Chart'
    }
}

Here's a link to the Chartjs documentation

- Jedidiah

---

我不相信在2015年我提出这个问题时文档中有标题可用，但现在知道有了。 - Todd Skelton

Answer 3

在选项中添加此参数。

    multiTooltipTemplate: "<%= datasetLabel %> - <%= value %>"

- Ali