How to move labels' position on Chart.js pie

问题

I'm using Chart.js and I'm trying to move the labels on my Pie chart outside of the pie area (see red X's):

This my code right now:

<div class="container" id="pieContainer">
    <h4 class="title">Title</h4>
    <center><canvas id="pie"></canvas></center>
</div>

<script>                                  
    var pieData = [
    {
        value: 39,
        color:"#335478",
        label: "Blue"
    },
    {
        value : 4,
        color : "#7f7f7f",
        label: "Grey"
    },
    {
        value : 57,
        color : "#99cb55",
        label: "Green"
    }
    ];

    var optionsPie = {
        responsive : true,
        tooltipEvents: [],
        showTooltips: true,
        onAnimationComplete: function() {
             this.showTooltip(this.segments, true);
        },
        tooltipTemplate: "<%= label %> - <%= value %>%"
    };
    new Chart(document.getElementById("pie").getContext("2d")).Pie(pieData, optionsPie);
</script>

I don't want to use legends and I couldn't find a built-in method to move labels. Is there a way to do that without changing chart.js? What's the best way to achieve my goal?

回答1:

Just extend the chart to do this. If your labels are static, it might be simpler to just change the tooltipPosition method instead.

---

Preview

---

Script

Chart.types.Pie.extend({
    name: "PieAlt",
    initialize: function(data){
        Chart.types.Pie.prototype.initialize.apply(this, arguments);

        var requiredSpace = 0;
        for (var i = 0; i < data.length; i++)
            requiredSpace = Math.max(ctx.measureText(Chart.helpers.template(this.options.tooltipTemplate, data[i])).width, requiredSpace);
        this.outerRadius -= (requiredSpace + 20);
    },
    draw: function(data){
        Chart.types.Pie.prototype.draw.apply(this, arguments);

        var self = this;
        ctx.save();
        ctx.font = Chart.helpers.fontString(self.options.scaleFontSize, self.options.scaleFontStyle, self.options.scaleFontFamily);
                ctx.textBaseline = "middle";
        self.segments.forEach(function (segment) {
            var outerEdge = Chart.Arc.prototype.tooltipPosition.apply({
                x: this.chart.width / 2,
                y: this.chart.height / 2,
                startAngle: segment.startAngle,
                endAngle: segment.endAngle,
                outerRadius: segment.outerRadius * 2 + 20,
                innerRadius: 0
            })

            var normalizedAngle = (segment.startAngle + segment.endAngle) / 2;
            while (normalizedAngle > 2 * Math.PI) {
                normalizedAngle -= (2 * Math.PI)
            }

            if (normalizedAngle < (Math.PI * 0.4) || (normalizedAngle > Math.PI * 1.5))
                ctx.textAlign = "start";
            else if (normalizedAngle > (Math.PI * 0.4) && (normalizedAngle < Math.PI * 0.6)) {
                outerEdge.y += 5;
                ctx.textAlign = "center";
            }
            else if (normalizedAngle > (Math.PI * 1.4) && (normalizedAngle < Math.PI * 1.6)) {
                outerEdge.y - 5;
                ctx.textAlign = "center";
            }
            else
                ctx.textAlign = "end";

            ctx.fillText(Chart.helpers.template(self.options.tooltipTemplate, segment), outerEdge.x, outerEdge.y);
        });

        ctx.restore();
    }
});

and then

new Chart(ctx).PieAlt(data, {
    showTooltips: false
});

---

Fiddle - http://jsfiddle.net/h8rggkhp/

回答2:

It looks like you control the x and y position of the tooltips:

var myPieChart = new Chart(ctx).Pie(data, {
    customTooltips: function(tooltip) {

        // tooltip will be false if tooltip is not visible or should be hidden
        if (!tooltip) {
            return;
        }

        // Otherwise, tooltip will be an object with all tooltip properties like:

        // tooltip.caretHeight
        // tooltip.caretPadding
        // tooltip.chart
        // tooltip.cornerRadius
        // tooltip.fillColor
        // tooltip.font...
        // tooltip.text
        // tooltip.x
        // tooltip.y
        // etc...

    };
});

take a look at http://www.chartjs.org/docs/#doughnut-pie-chart-chart-options

回答3:

I recently ran into the same issue, and chartsjs-plugin-labels solved the issue for me.

Example:

import {Chart} from 'chartjs';
import 'chartjs-plugin-labels';

let options = {
  plugins: {
    labels: {
      position: 'outside',
      render: (args) => {
        return `${args.label}: ${args.value}%`;
      }
    }
  }
}

let data = {
  datasets: [
    {
      data: [39, 4, 57],
      labels: ['Blue', 'Gray', 'Green'],
    },
  ],
}

new Chart(ctx, {
  type: 'pie',
  data: data,
  options: options
}

来源：https://stackoverflow.com/questions/36209074/how-to-move-labels-position-on-chart-js-pie