当使用charts_flutter包时，我如何使用从提供程序文件中获得的值来设置条形图的颜色

Question

我一直在尝试用提供者文件中的值设置条形图中条形图的颜色，这样我就可以更改其他活动的颜色。如果我直接把颜色值像这个

colorFn: (Kpi kpi, _) => charts.ColorUtil.fromDartColor(Color(0xff000000)),

它是有效的。

但是试着像这样做

colorFn: (Kpi kpi, _) => charts.ColorUtil.fromDartColor(Color(context.watch<Providers>().colorAlpha)),

它不起作用。

我收到以下错误

I/flutter ( 1999): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter ( 1999): The following NoSuchMethodError was thrown during performLayout():
I/flutter ( 1999): The method '&' was called on null.
I/flutter ( 1999): Receiver: null
I/flutter ( 1999): Tried calling: &(4294967295)
I/flutter ( 1999):
I/flutter ( 1999): The relevant error-causing widget was:
I/flutter ( 1999):   ChartContainer<String>
I/flutter ( 1999):   file:///C:/flutter/.pub-cache/hosted/pub.dartlang.org/charts_flutter-0.9.0/lib/src/base_chart_state.dart:89:32
I/flutter ( 1999): 
I/flutter ( 1999): When the exception was thrown, this was the stack:
I/flutter ( 1999): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
I/flutter ( 1999): #1      new Color (dart:ui/painting.dart:109:42)
I/flutter ( 1999): #2      _AnalyticspageState.build.<anonymous closure> (package:GapHub/screens/analyticspage.dart:86:42)
I/flutter ( 1999): #3      new Series.<anonymous closure> (package:charts_common/src/data/series.dart:143:56)
I/flutter ( 1999): #4      DomainHighlighter._updateColorFunctions.<anonymous closure>.<anonymous closure> (package:charts_common/src/chart/common/behavior/domain_highlighter.dart:53:40)
I/flutter ( 1999): #5      BaseBarRenderer.update.<anonymous closure> (package:charts_common/src/chart/bar/base_bar_renderer.dart:407:31)
I/flutter ( 1999): #6      List.forEach (dart:core-patch/growable_array.dart:302:8)
I/flutter ( 1999): #7      BaseBarRenderer.update (package:charts_common/src/chart/bar/base_bar_renderer.dart:342:23)
I/flutter ( 1999): #8      BaseChart.onPostLayout.<anonymous closure> (package:charts_common/src/chart/common/base_chart.dart:584:37)
I/flutter ( 1999): #9      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:377:8)
I/flutter ( 1999): #10     BaseChart.onPostLayout (package:charts_common/src/chart/common/base_chart.dart:583:10)
I/flutter ( 1999): #11     CartesianChart.onPostLayout (package:charts_common/src/chart/cartesian/cartesian_chart.dart:428:11)
I/flutter ( 1999): #12     BaseChart.layout (package:charts_common/src/chart/common/base_chart.dart:398:7)
I/flutter ( 1999): #13     ChartContainerRenderObject.performLayout (package:charts_flutter/src/chart_container.dart:215:12)

Answer 1

我这样做的方法是

return charts.Color.fromHex(
code: "#${Colors.primaries[Random().nextInt(Colors.primaries.length)].value}");