anchor.diff:      btnCharts =$['btnCharts'];
       startDate =$['startDate'];
       endDate =$['endDate'];
  -    //mainChart.on['google-chart-select'].listen(sendMessage);
  +
       selectPair.on['tap'].listen(loadChartDialog);
       btnCharts.on['tap'].listen(loadChart);
       loadCurrencyPairs();
  
positive.code: 
  
      mainChart.rows= await dailyValues(startDate.value,endDate.value,pair);
  
    }
  
  
negative.code:   }
    sendMessage(Event e)
    {
  
      window.alert(mainChart.selection[0]["row"].toString());
    }
  
    loadChartDialog(Event e)
  