在图表js中鼠标悬停时绘制水平线和垂直线

Question

我在创建折线图时遇到图表 js 问题。我想创建一个包含指定数据的图表，并且在将鼠标悬停在交点上时还需要有水平线和垂直线。我能够在悬停时创建垂直线，但找不到任何可以绘制两条线的解决方案。这是我在悬停时绘制垂直线的代码。

    window.lineOnHover = function(){        
        Chart.defaults.LineWithLine = Chart.defaults.line;
        Chart.controllers.LineWithLine = Chart.controllers.line.extend({
        draw: function(ease) {
          Chart.controllers.line.prototype.draw.call(this, ease);

          if (this.chart.tooltip._active && this.chart.tooltip._active.length) {
             var activePoint = this.chart.tooltip._active[0],
                 ctx = this.chart.ctx,
                 x = activePoint.tooltipPosition().x,
                 topY = this.chart.legend.bottom,
                 bottomY = this.chart.chartArea.bottom;

             // draw line
             ctx.save();
             ctx.beginPath();
             ctx.moveTo(x, topY);
             ctx.lineTo(x, bottomY);
             ctx.lineWidth = 1;
             ctx.setLineDash([3,3]);
             ctx.strokeStyle = '#FF4949';
             ctx.stroke();
             ctx.restore();
          }
        }
        });
    }


//create chart
var backhaul_wan_mos_chart = new Chart(backhaul_wan_mos_chart, {
    type: 'LineWithLine',
    data: {
        labels: ['Aug 1', 'Aug 2', 'Aug 3', 'Aug 4', 'Aug 5', 'Aug 6', 'Aug 7', 'Aug 8'],
        datasets: [{
                label: 'Series 1',
                data: [15, 16, 17, 18, 16, 18, 17, 14, 19, 16, 15, 15, 17],
                pointRadius: 0,
                fill: false,
                borderDash: [3, 3],
                borderColor: '#0F1731',
//                    backgroundColor: '#FF9CE9',
//                    pointBackgroundColor: ['#FB7BDF'],
                borderWidth: 1
            }],
//                lineAtIndex: 2,
    },
    options: {
        tooltips: {
            intersect: false
        },
        legend: {
            display: false
        },
        scales: {
            xAxes: [{
                    gridLines: {
                        offsetGridLines: true
                    },
                    ticks: {
                        fontColor: '#878B98',
                        fontStyle: "600",
                        fontSize: 10,
                        fontFamily: "Poppins"
                    }
                }],
            yAxes: [{
                    display: true,
                    stacked: true,
                    ticks: {
                        min: 0,
                        max: 50,
                        stepSize: 10,
                        fontColor: '#878B98',
                        fontStyle: "500",
                        fontSize: 10,
                        fontFamily: "Poppins"
                    }
                }]
        },
        responsive: true,
    }
});

我的代码输出如下WAN MoS 分数图 --

因此，当我将鼠标悬停在交点（绘制）上时，我希望将水平线与同一垂直线放在一起..

请帮助我的人..提前致谢。

Answer 1

我在我的一个项目的以前的版本中正是这样做的（但只是垂直线）。不幸的是，此功能已被删除，但仍然可以通过我的 github.

访问旧的源代码文件

关键是这段代码：

Chart.defaults.LineWithLine = Chart.defaults.line;
Chart.controllers.LineWithLine = Chart.controllers.line.extend({
   draw: function(ease) {
      Chart.controllers.line.prototype.draw.call(this, ease);

      if (this.chart.tooltip._active && this.chart.tooltip._active.length) {
         var activePoint = this.chart.tooltip._active[0],
             ctx = this.chart.ctx,
             x = activePoint.tooltipPosition().x,
             topY = this.chart.legend.bottom,
             bottomY = this.chart.chartArea.bottom;

         // draw line
         ctx.save();
         ctx.beginPath();
         ctx.moveTo(x, topY);
         ctx.lineTo(x, bottomY);
         ctx.lineWidth = 0.5;
         ctx.strokeStyle = '#A6A6A6';
         ctx.stroke();
         ctx.restore();
      }
   }
});

另一个警告是上面的代码适用于 Chart.js 2.8，我知道 Chart.js 的当前版本是 3.1。我还没有阅读关于更新的官方手册，但我个人的经验是，这个更新不是 100% 向后兼容的——所以如果你需要 Chart.js，我不确定它是否仍然有效 3.（但你肯定可以首先尝试 2.8，如果可行，您可以通过某种方式调整代码以使其在 3.1 上运行)

Answer 2

您可以为从工具提示获得的 y 坐标添加第二个绘图块，首先移动到 chartArea 的左侧，您可以获得底部和顶部的相同方式，然后移动到右上同Y

Chart.defaults.LineWithLine = Chart.defaults.line;
Chart.controllers.LineWithLine = Chart.controllers.line.extend({
  draw: function(ease) {
    Chart.controllers.line.prototype.draw.call(this, ease);

    if (this.chart.tooltip._active && this.chart.tooltip._active.length) {
      var activePoint = this.chart.tooltip._active[0],
        ctx = this.chart.ctx,
        x = activePoint.tooltipPosition().x,
        y = activePoint.tooltipPosition().y,
        topY = this.chart.legend.bottom,
        bottomY = this.chart.chartArea.bottom,
        left = this.chart.chartArea.left,
        right = this.chart.chartArea.right;


      // Set line opts
      ctx.save();
      ctx.lineWidth = 1;
      ctx.setLineDash([3, 3]);
      ctx.strokeStyle = '#FF4949';

      // draw vertical line      
      ctx.beginPath();
      ctx.moveTo(x, topY);
      ctx.lineTo(x, bottomY);
      ctx.stroke();

      // Draw horizontal line
      ctx.beginPath();
      ctx.moveTo(left, y);
      ctx.lineTo(right, y);
      ctx.stroke();

      ctx.restore();
    }
  }
});

var options = {
  type: 'LineWithLine',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
        label: '# of Votes',
        data: [12, 19, 3, 5, 2, 3],
        borderWidth: 1
      },
      {
        label: '# of Points',
        data: [7, 11, 5, 8, 3, 7],
        borderWidth: 1
      }
    ]
  },
  options: {
  }
}

var ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);

<body>
  <canvas id="chartJSContainer" width="600" height="400"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.js"></script>
</body>

编辑：

您应该为此使用自定义插件，因为您不会在每次移动光标时都绘制，您可以使用自定义插件强制执行此操作：

const options = {
  type: 'line',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
        label: '# of Votes',
        data: [12, 19, 3, 5, 2, 3],
        borderWidth: 1
      },
      {
        label: '# of Points',
        data: [7, 11, 5, 8, 3, 7],
        borderWidth: 1
      }
    ]
  },
  options: {
    plugins: {
      corsair: {
        dash: [2, 2],
        color: 'red',
        width: 3
      }
    }
  },
  plugins: [{
    id: 'corsair',
    afterInit: (chart) => {
      chart.corsair = {
        x: 0,
        y: 0
      }
    },
    afterEvent: (chart, evt) => {
      const {
        chartArea: {
          top,
          bottom,
          left,
          right
        }
      } = chart;
      const {
        x,
        y
      } = evt;
      if (x < left || x > right || y < top || y > bottom) {
        chart.corsair = {
          x,
          y,
          draw: false
        }
        chart.draw();
        return;
      }

      chart.corsair = {
        x,
        y,
        draw: true
      }

      chart.draw();
    },
    afterDatasetsDraw: (chart, _, opts) => {
      const {
        ctx,
        chartArea: {
          top,
          bottom,
          left,
          right
        }
      } = chart;
      const {
        x,
        y,
        draw
      } = chart.corsair;

      if (!draw) {
        return;
      }

      ctx.lineWidth = opts.width || 0;
      ctx.setLineDash(opts.dash || []);
      ctx.strokeStyle = opts.color || 'black'

      ctx.save();
      ctx.beginPath();
      ctx.moveTo(x, bottom);
      ctx.lineTo(x, top);
      ctx.moveTo(left, y);
      ctx.lineTo(right, y);
      ctx.stroke();
      ctx.restore();
    }
  }]
}

const ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);

<body>
  <canvas id="chartJSContainer" width="600" height="400"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.js"></script>
</body>

编辑：

v3 的更新答案

const options = {
  type: 'line',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
        label: '# of Votes',
        data: [12, 19, 3, 5, 2, 3],
        borderWidth: 1
      },
      {
        label: '# of Points',
        data: [7, 11, 5, 8, 3, 7],
        borderWidth: 1
      }
    ]
  },
  options: {
    plugins: {
      corsair: {
        dash: [2, 2],
        color: 'red',
        width: 3
      }
    }
  },
  plugins: [{
    id: 'corsair',
    afterInit: (chart) => {
      chart.corsair = {
        x: 0,
        y: 0
      }
    },
    afterEvent: (chart, evt) => {
      const {
        chartArea: {
          top,
          bottom,
          left,
          right
        }
      } = chart;
      const {
        event: {
          x,
          y
        }
      } = evt;
      if (x < left || x > right || y < top || y > bottom) {
        chart.corsair = {
          x,
          y,
          draw: false
        }
        chart.draw();
        return;
      }

      chart.corsair = {
        x,
        y,
        draw: true
      }

      chart.draw();
    },
    afterDatasetsDraw: (chart, _, opts) => {
      const {
        ctx,
        chartArea: {
          top,
          bottom,
          left,
          right
        }
      } = chart;
      const {
        x,
        y,
        draw
      } = chart.corsair;

      if (!draw) {
        return;
      }

      ctx.lineWidth = opts.width || 0;
      ctx.setLineDash(opts.dash || []);
      ctx.strokeStyle = opts.color || 'black'

      ctx.save();
      ctx.beginPath();
      ctx.moveTo(x, bottom);
      ctx.lineTo(x, top);
      ctx.moveTo(left, y);
      ctx.lineTo(right, y);
      ctx.stroke();
      ctx.restore();
    }
  }]
}

const ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);

<body>
  <canvas id="chartJSContainer" width="600" height="400"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.4/Chart.js"></script>
</body>

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