Ionic using multiple chart.js canvas in the same page

Question

Does anyone have an example for using multiple canvas in the same page?

I have something like this in the HTML:

<div style="height: 138px" *ngFor="let item of listItems; let i = index">
    <canvas #pieCanvas id="pieCanvas{{i}}" style="width: 100px !important; height: 100px !important"></canvas>
  </div>

In the .ts file:

@ViewChild("pieCanvas") pieCanvas: ElementRef;

for (var j = 0; j < chartcount; j++)
{

   let htmlRef = document.getElementById('pieCanvas'+j);
   this.pieCanvas = new Chart(htmlRef, piechartdata);

}

Getting always null is not an object (evaluating 'item.length') error.

With only one chart it works perfect, but there I use sth. like

this.barCanvas = new Chart(this.barCanvas.nativeElement......

I Googled, but couldn't find a solution.

Thanks for your help!

Answer 1

I have found the solution....finally!!!

In html:

<canvas #barCanvas id="barCanvaslist{{i}}"></canvas>

Then in ts: @ViewChildren('barCanvas') Canvaslist: QueryList; charts: any;

and afterwards:

this.Canvaslist.changes.subscribe(c => 
{ c.toArray().forEach(item => 
  { 
    this.Canvaslist = new Chart(item.nativeElement, pieData[j]);
    j = j+1;
  }) 
});

this does the trick