Flutter / Dart 错误：无法将参数类型“Null Function(Key)”分配给参数类型“void Function(Object)”答案

【问题标题】：Flutter / Dart Error: The argument type 'Null Function(Key)' can't be assigned to the parameter type 'void Function(Object)'Flutter / Dart 错误：无法将参数类型“Null Function(Key)”分配给参数类型“void Function(Object)”
【发布时间】：2020-05-15 00:55:35
【问题描述】：

Android Studio：在 iPhone 11 Pro Max 上以调试模式启动 lib/main.dart...

Compiler message:
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_flex.dart:727:18: Error: The argument type 'Null Function(Key)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Key' is from 'package:flutter/src/foundation/key.dart' ('/Users/[User]/Development/flutter/packages/flutter/lib/src/foundation/key.dart').
 - 'Object' is from 'dart:core'.
        onLeave: (Key leaving) {},
                 ^
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_wrap.dart:951:18: Error: The argument type 'Null Function(int)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Object' is from 'dart:core'.
        onLeave: (int leaving) {},
                 ^
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_wrap.dart:957:18: Error: The argument type 'Null Function(int)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Object' is from 'dart:core'.
        onLeave: (int leaving) {},
                 ^
/Users/[User]/.pub-cache/hosted/pub.dartlang.org/reorderables-0.2.12/lib/src/widgets/reorderable_sliver.dart:842:18: Error: The argument type 'Null Function(int)' can't be assigned to the parameter type 'void Function(Object)'.
 - 'Object' is from 'dart:core'.
        onLeave: (int leaving) {},
                 ^
Target kernel_snapshot failed: Exception: Errors during snapshot creation: null
Failed to build bundle.
Error launching application on iPhone 11 Pro Max.

无法通过这个问题得到答案，任何帮助将不胜感激☃

【问题讨论】：

尝试清除缓存
感谢@Doc 清除缓存通常会有所帮助，这次不行

标签： android-studio flutter dart compiler-errors

【解决方案1】：

Simon Binder 通过 dart-lang/TALK-general 回答：

这是您可能依赖的 reorderables 包中的错误。报告和解决方法在这里：hanshengchiu/reorderables#52

pubspec.yaml 中的更改：

#  reorderables: ^0.2.12
  reorderables:
    git:
      url: git://github.com/hanshengchiu/reorderables.git

【讨论】：