升级到 flutter 3.0.0 后，运行应用程序时开始出现问题，
\n（该应用程序可以运行，但终端中出现错误（警告））。
\n这似乎是一个绑定问题。
\n错误（警告）说：\n警告：null 感知操作 \'!\' 的操作数具有类型 \'WidgetsBinding\'，其中排除 null。
\n: Warning: Operand of null-aware operation \'!\' has type \'WidgetsBinding\' which excludes null.\n../\xe2\x80\xa6/src/keyboard_visibility.dart:21\n- \'WidgetsBinding\' is from \'package:flutter/src/widgets/binding.dart\' (\'../../../fvm/versions/3.0.0/packages/flutter/lib/src/widgets/binding.dart\').\npackage:flutter/\xe2\x80\xa6/widgets/binding.dart:1\n WidgetsBinding.instance!.addObserver(this);\n\n ^\n: Warning: Operand of null-aware operation \'!\' has type \'WidgetsBinding\' which excludes null.\n../\xe2\x80\xa6/src/keyboard_visibility.dart:37\n- \'WidgetsBinding\' is from \'package:flutter/src/widgets/binding.dart\' (\'../../../fvm/versions/3.0.0/packages/flutter/lib/src/widgets/binding.dart\').\npackage:flutter/\xe2\x80\xa6/widgets/binding.dart:1\n WidgetsBinding.instance!.removeObserver(this);\n ^\n: Warning: Operand of null-aware operation \'!\' has type \'WidgetsBinding\' which excludes null.\n../\xe2\x80\xa6/src/bot_toast_init.dart:15\n- \'WidgetsBinding\' is from \'package:flutter/src/widgets/binding.dart\' (\'../../../fvm/versions/3.0.0/packages/flutter/lib/src/widgets/binding.dart\').\npackage:flutter/\xe2\x80\xa6/widgets/binding.dart:1\n WidgetsBinding.instance!.addObserver(this);\n ^\n: Warning: Operand of null-aware operation \'!\' …