Chart.js 2.0 - 垂直线

Question

谁能告诉我如何扩展 Chart.js v2.0。我需要折线图中的垂直线，我想实现类似于 http://jsfiddle.net/dbyze2ga/ 的东西.

Chart.types.Line.extend({
name: "LineWithLine",
draw: function () {
    Chart.types.Line.prototype.draw.apply(this, arguments);

    var point = this.datasets[0].points[this.options.lineAtIndex]
    var scale = this.scale

    // draw line
    this.chart.ctx.beginPath();
    this.chart.ctx.moveTo(point.x, scale.startPoint + 24);
    this.chart.ctx.strokeStyle = '#ff0000';
    this.chart.ctx.lineTo(point.x, scale.endPoint);
    this.chart.ctx.stroke();

    // write TODAY
    this.chart.ctx.textAlign = 'center';
    this.chart.ctx.fillText("TODAY", point.x, scale.startPoint + 12);
}
});

new Chart(ctx).LineWithLine(data, {
                            datasetFill : false,
                            lineAtIndex: 2
 });

Answer 1

更新 : 见 https://stackoverflow.com/a/45092928/360067使用 Chart Annotations 插件获得更简单、更强大的解决方案。

您可以扩展 line键入以添加对绘制线条的支持

预览



脚本

var originalLineDraw = Chart.controllers.line.prototype.draw;
Chart.helpers.extend(Chart.controllers.line.prototype, {
  draw: function() {
    originalLineDraw.apply(this, arguments);

    var chart = this.chart;
    var ctx = chart.chart.ctx;

    var index = chart.config.data.lineAtIndex;
    if (index) {
      var xaxis = chart.scales['x-axis-0'];
      var yaxis = chart.scales['y-axis-0'];

      ctx.save();
      ctx.beginPath();
      ctx.moveTo(xaxis.getPixelForValue(undefined, index), yaxis.top);
      ctx.strokeStyle = '#ff0000';
      ctx.lineTo(xaxis.getPixelForValue(undefined, index), yaxis.bottom);
      ctx.stroke();
      ctx.restore();
    }
  }
});

进而

var config = {
  type: 'line',
  data: {
    labels: ...
    datasets: [
        ...
    ],
    lineAtIndex: 2
  }
};

fiddle - http://jsfiddle.net/mn8x6fso/