title: How to display data value of an item on click inside flutter charts
body: <p>I'm using charts_flutter library on one of my projects and I would like to display the data value on clicking on each Bar chart item. Is it possible?</p>
  
  <pre><code>var data = [
    new ClicksPerYear('2016', 12, Colors.red),
    new ClicksPerYear('2017', 42, Colors.blue),
    new ClicksPerYear('2018', counter, Colors.green),
  ];
  
  var series = [
    new charts.Series(
      id: 'Clicks',
      data: data,
      domainFn: (ClicksPerYear clickData, _) =&gt; clickData.year,
      measureFn: (ClicksPerYear clickData, _) =&gt; clickData.clicks,
      colorFn: (ClicksPerYear clickData, _) =&gt; clickData.color,
    )
  ];
  var barChart = new charts.BarChart(
        series,
        animate: true,
  );
  </code></pre>