Some of the newer version (since 0.5.3) of extended_image has some BREAKING CHANGES that any SDK version below current stable cannot use this package normally.

So in order to use the package below the stable SDK version (such as 1.12), you must specific your pubspec.yaml with extended_image and extended_image_library to a fixed version, as the code below。
Though, we STRONGLY SUGGEST you to use the latest stable version of Flutter SDK.

较新的extended_image（自0.5.3起）的部分版本，包含了一些非向前兼容的改动，使得该依赖无法在Flutter SDK版本低于当前稳定版本的环境下使用。

若您需要在低于SDK版本（比如1.12.13）的环境下使用该依赖，必须在pubspec.yaml内同时指定extended_image和extended_image_library为指定或更低的版本，如代码所示。
我们仍然强烈建议您使用最新的稳定渠道的Flutter SDK。

dependencies:
  extended_image: 0.7.2
  extended_image_library: 0.2.1