How do I fix this error: Offset argument contained a NaN value. 'dart:ui/painting.dart': Failed assertion: line 43: '<optimized out>'

Question

I am trying to create a time series chart with tooltips in flutter, but I can't manage to overcome this error message. "Offset argument contained a NaN value. 'dart:ui/painting.dart': Failed assertion: line 43: ''". https://github.com/google/charts/issues/58 is where I got this code from, but nobody else seems to have this issue. The same error message always appears when trying other types of charts and different blocks of code found on that github page. Here is the relevant code:

import 'package:charts_flutter/flutter.dart' as charts;
import 'package:flutter/material.dart';
import 'dart:math';
import 'package:charts_flutter/flutter.dart';
import 'package:charts_flutter/src/text_element.dart' as text;
import 'package:charts_flutter/src/text_style.dart' as style;

class CustomMeasureTickCount extends StatelessWidget {
  final List<charts.Series> seriesList;
  final bool animate;
  static String pointerValue;
  CustomMeasureTickCount(this.seriesList, {this.animate});

  factory CustomMeasureTickCount.withSampleData() {
    return new CustomMeasureTickCount(
      _createSampleData(),
      animate: false,
    );
  }

  @override
  Widget build(BuildContext context) {
    return new charts.TimeSeriesChart(seriesList,
        animate: animate,
        behaviors: [
          LinePointHighlighter(symbolRenderer: CustomCircleSymbolRenderer())
        ],
        selectionModels: [
          SelectionModelConfig(changedListener: (SelectionModel model) {
            if (model.hasDatumSelection)
              pointerValue = model.selectedSeries[0]
                  .measureFn(model.selectedDatum[0].index)
                  .toString();
          })
        ],

        /// Customize the measure axis to have 10 ticks
        primaryMeasureAxis: new charts.NumericAxisSpec(
            tickProviderSpec:
                new charts.BasicNumericTickProviderSpec(desiredTickCount: 10)));
  }

  /// Create one series with sample hard coded data.
  static List<charts.Series<MyRow, DateTime>> _createSampleData() {
    final data = [
      new MyRow(new DateTime(2017, 9, 25), 6),
      new MyRow(new DateTime(2017, 9, 26), 8),
      new MyRow(new DateTime(2017, 9, 27), 6),
      new MyRow(new DateTime(2017, 9, 28), 9),
      new MyRow(new DateTime(2017, 9, 29), 11),
      new MyRow(new DateTime(2017, 9, 30), 15),
      new MyRow(new DateTime(2017, 10, 01), 25),
      new MyRow(new DateTime(2017, 10, 02), 33),
      new MyRow(new DateTime(2017, 10, 03), 27),
      new MyRow(new DateTime(2017, 10, 04), 31),
      new MyRow(new DateTime(2017, 10, 05), 23),
    ];

    return [
      new charts.Series<MyRow, DateTime>(
        id: 'Cost',
        domainFn: (MyRow row, _) => row.timeStamp,
        measureFn: (MyRow row, _) => row.cost,
        data: data,
        colorFn: (_, __) => charts.MaterialPalette.indigo.shadeDefault,
      )
    ];
  }
}

/// Sample time series data type.
class MyRow {
  final DateTime timeStamp;
  final int cost;
  MyRow(this.timeStamp, this.cost);
}

class CustomCircleSymbolRenderer extends CircleSymbolRenderer {
  @override
  void paint(ChartCanvas canvas, Rectangle bounds,
      {List dashPattern,
      Color fillColor,
      FillPatternType fillPattern,
      Color strokeColor,
      double strokeWidthPx}) {
    super.paint(canvas, bounds,
        dashPattern: dashPattern,
        fillColor: fillColor,
        fillPattern: fillPattern,
        strokeColor: strokeColor,
        strokeWidthPx: strokeWidthPx);
    canvas.drawRect(
        Rectangle(bounds.left - 5, bounds.top - 30, bounds.width + 10,
            bounds.height + 10),
        fill: Color.white);
    var textStyle = style.TextStyle();
    textStyle.color = Color.black;
    textStyle.fontSize = 15;
    canvas.drawText(
        text.TextElement(CustomMeasureTickCount.pointerValue, style: textStyle),
        (bounds.left).round(),
        (bounds.top - 28).round());
  }
}

Answer 1

The error occurs because of an new event occuring like navigating to a new page while the textfield is in foccus. To fox the issue just simply remove focuss from the textfield.

For example FocusScope.of(context).requestFocus(new FocusNode());