我遇到很多“ NoSuchMethodError：”“ 错误。
我有一个带有角度的大型Web应用程序。现在我正在使用dart 2.6.1。
首先，我有一个案例，其中定义了一个static const变量（例如static Duration period = Duration(seconds: 30);）。
使用此变量导致该错误。删除const关键字，一切似乎都可以正常工作。 但是后来我从一个角度组件中得到了同样的错误。
我有很多依赖关系，恐怕这会给编译器造成一些奇怪的问题。
有任何提示吗？
我不知道const变量是否有内存限制，在这种情况下，如何检查该限制（或增加该限制）？ 我可以做些什么来验证问题所在？ 以下是堆栈跟踪的一部分：
Error_handler: reason NoSuchMethodError: '<Unexpected Null Value>'
method not found
Receiver: null
Arguments: [], exception, NoSuchMethodError: '<Unexpected Null Value>'
method not found
Receiver: null
Arguments: [], stack dart:sdk_internal createTimer
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 210:25 [_createTimer]
dart:sdk_internal new
package:angular_components/material_popup/material_popup.dart 510:25 [_onPopupOpened]
package:angular_components/material_popup/material_popup.dart 472:11 <fn>
package:stack_trace <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 144:18 <fn>
dart:sdk_internal runUnary
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 141:18 [_runUnary]
dart:sdk_internal add
package:angular_components/material_popup/material_popup.dart 862:29 <fn>
package:stack_trace <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 144:18 <fn>
dart:sdk_internal runUnary
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 141:18 [_runUnary]
package:stack_trace <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 144:18 <fn>
dart:sdk_internal runUnary
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 141:18 [_runUnary]
package:stack_trace <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 132:18 <fn>
dart:sdk_internal run
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 129:18 [_run]
dart:sdk_internal <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 117:11 <fn>
package:stack_trace <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 132:18 <fn>
dart:sdk_internal run
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 129:18 [_run]
dart:sdk_internal listen
package:angular_components/material_popup/material_popup.dart 468:50 [_open]
package:stack_trace <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 132:18 <fn>
dart:sdk_internal run
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 129:18 [_run]
dart:sdk_internal <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 117:11 <fn>
package:stack_trace <fn>
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 132:18 <fn>
dart:sdk_internal run
package:angular/src/core/change_detection/..%5Czone%5Cng_zone.dart 129:18 [_run]
dart:sdk_internal scheduleMicrotask
package:angular_components/material_popup/material_popup.dart 338:9 set visible
编辑1：
我移回2.5.2，一切工作正常。 然后我安装了2.6.1，问题再次出现。 所以，我认为这与2.6.1有关