如何在 Angular 图表的圆环图中添加标题?

How to add title inside doughnut chart in Angular Chart?

我正在使用 doughnut chart in Angular Chart. I want to place some text in the center of the doughnut. I've read this question's 个答案,但其中 none 个对我有用,因为我有工具提示,并且出于某种原因,当您将鼠标悬停在图表上时,文本会消失。此外,我需要提供来自 "outside" 的文本 - 自定义文本,例如一个标题。

所以,我的想法是:

var options = {
    innerTitle = "This should be placed in the center of the doughnut"
}

有什么想法吗?

编辑: 我添加了 JS Bin by changing a few lines of this answer.

我会尝试一下。这种方法只是将标签绝对定位在 canvas 之上。唯一的缺点是您必须同时设置 #canvas-holdercanvas 的高度和宽度。我创建了一个 plunkr 来演示:http://plnkr.co/edit/kT63Ur5ebNm1A6bQWSlO

<!-- css -->
#canvas-holder {
  height: 100px;
  width: 100px;
  position: relative;
}

.chart-title {
  position: absolute;
  left: 0;
  right: 0;
  margin: 0 auto;
  top: 50%;
  transform: translateY(-50%);
  width: 100%;
  text-align: center;
}

<!-- canvas -->
<div id="canvas-holder">
    <label class="chart-title">My Chart Title</label>
    <canvas id="chart-area" height="100" width="100" />
</div>

这个我也试了一下。此方法基于@RYUUSEiiSTAR 的方法和您创建的 link。仍然需要进行正确的计算以使文本居中。
我创建了一个 plunkr 来演示:https://jsfiddle.net/onoc2wmx/(新 Link)。

更新
经过几个小时的黑客攻击,我更新了代码,以便您可以修改字体大小,现在它可以响应了。现在它看起来像这样:

var options = { 
  showTooltips : true,
  animation: true,
  percentageInnerCutout : 70,
  onAnimationComplete: innerTextFunction
};

var chartCtx = $("#canvas").get(0).getContext("2d");
var textCtx = $("#text").get(0).getContext("2d");
var chart = new Chart(chartCtx).Doughnut(doughnutData, options);


function innerTextFunction() {
  var canvasWidthvar = $('#canvas').width();
  var canvasHeight = $('#canvas').height();
  var constant = 114;
  var fontsize = (canvasHeight/constant).toFixed(2);
  textCtx.font = fontsize + "em Verdana";
  textCtx.textBaseline="middle"; 
  var total = 0;
  $.each(doughnutData,function() {
    total += parseInt(this.value,10);
  });
  var tpercentage = ((doughnutData[0].value/total)*100).toFixed(2)+"%";
  var textWidth = textCtx.measureText(tpercentage).width;
  var txtPosx = Math.round((canvasWidthvar - textWidth)/2);
  textCtx.fillText(tpercentage, txtPosx, canvasHeight/4);
}     


<div style="position: relative;">
    <canvas id="text" style="z-index: 1; position: absolute; 
                   left: 0px; top: 0px; width: 300px; height: 300px;"></canvas>
    <canvas id="canvas" style="z-index: 2; position: absolute; 
                   left: 0px; top: 0px; width: 300px; height: 300px;"></canvas>
</div>

只需调整 bottomfont-size css

上的 %
<div class="row charDonut">
   <div class="chartTitle">
     {{vm.totalTask}}<br>
     {{vm.chartTitle}}
   </div>
   <canvas id="doughnut" class="chart chart-doughnut">
   </canvas>
</div>

.row.charDonut{
  position: relative;
}

.chartTitle{
  position: absolute;
  left: 0;
  right: 0;
  bottom: 36%; <<----
  text-align: center;
  font-size: 2em; <<----
}