如何在Chart.js v2.0中的标签上添加OnClick事件？

Question

寻找一种在chartjs 2.0中的"label"元素上添加onClick句柄的方法因为只要点击Char.js V2.0 RadarChart中的任何一个标签属性,使用下面的方法将在console.log中返回"undifined".

var data = {
    // below line is the labels 
    labels: ["Eating", "Drinking", "Sleeping", "Designing", "Coding", "Cycling", "Running"],
    datasets: [
        {
            label: "My First dataset", //this only shows as legend, not label.

            backgroundColor: "rgba(179,181,198,0.2)",
            borderColor: "rgba(179,181,198,1)",
            pointBackgroundColor: "rgba(179,181,198,1)",
            pointBorderColor: "#fff",
            pointHoverBackgroundColor: "#fff",
            pointHoverBorderColor: "rgba(179,181,198,1)",
            data: [65, 59, 90, 81, 56, 55, 40]
        },
       ....

//Below is how to OnClick on chart points in chart.js V2, 
//However, it didn't apply to labels, will return "undifined" .   
$('#ChartV2').click(function(e) {
                var activePoints = myRadarChart.getElementsAtEvent(e);                  
                var firstPoint = activePoints[0];
                console.log(firstPoint);
                if (firstPoint !== undefined){
                   alert(firstPoint._index);                        
                }
 });

Answer 1

在chart.js 2.5(甚至可能更早)中,您可以在选项中添加onClick:

'legend' : {
    'onClick' : function (evt, item) {
                    console.log ('legend onClick', evt, item);
                },
    'display' : true,
    'labels' : ...

Answer 2

getElementsAtEvent仅检查图表的主要元素(条形图,点,扇区......).如果您也想考虑标签,则必须重新实现标签的功能.

您需要的大多数代码已在Chart.js库代码中以不同方法提供.只需复制粘贴/清理,如下所示.

脚本

你的点击处理应该是

$('#myChart').click(function (e) {
    var helpers = Chart.helpers;

    var eventPosition = helpers.getRelativePosition(e, myRadarChart.chart);
    var mouseX = eventPosition.x;
    var mouseY = eventPosition.y;

    var activePoints = [];
    // loop through all the labels
    helpers.each(myRadarChart.scale.ticks, function (label, index) {
        for (var i = this.getValueCount() - 1; i >= 0; i--) {
            // here we effectively get the bounding box for each label
            var pointLabelPosition = this.getPointPosition(i, this.getDistanceFromCenterForValue(this.options.reverse ? this.min : this.max) + 5);

            var pointLabelFontSize = helpers.getValueOrDefault(this.options.pointLabels.fontSize, Chart.defaults.global.defaultFontSize);
            var pointLabeFontStyle = helpers.getValueOrDefault(this.options.pointLabels.fontStyle, Chart.defaults.global.defaultFontStyle);
            var pointLabeFontFamily = helpers.getValueOrDefault(this.options.pointLabels.fontFamily, Chart.defaults.global.defaultFontFamily);
            var pointLabeFont = helpers.fontString(pointLabelFontSize, pointLabeFontStyle, pointLabeFontFamily);
            ctx.font = pointLabeFont;

            var labelsCount = this.pointLabels.length,
                halfLabelsCount = this.pointLabels.length / 2,
                quarterLabelsCount = halfLabelsCount / 2,
                upperHalf = (i < quarterLabelsCount || i > labelsCount - quarterLabelsCount),
                exactQuarter = (i === quarterLabelsCount || i === labelsCount - quarterLabelsCount);
            var width = ctx.measureText(this.pointLabels[i]).width;
            var height = pointLabelFontSize;

            var x, y;

            if (i === 0 || i === halfLabelsCount)
                x = pointLabelPosition.x - width / 2;
            else if (i < halfLabelsCount)
                x = pointLabelPosition.x;
            else
                x = pointLabelPosition.x - width;

            if (exactQuarter)
                y = pointLabelPosition.y - height / 2;
            else if (upperHalf)
                y = pointLabelPosition.y - height;
            else
                y = pointLabelPosition.y

            // check if the click was within the bounding box
            if ((mouseY >= y && mouseY <= y + height) && (mouseX >= x && mouseX <= x + width))
                activePoints.push({ index: i, label: this.pointLabels[i] });
        }
    }, myRadarChart.scale);

    var firstPoint = activePoints[0];
    if (firstPoint !== undefined) {
        alert(firstPoint.index + ': ' + firstPoint.label);
    }
});

小提琴 - http://jsfiddle.net/1Lngmtz7/