AWS Amplify for Flutter：已提示登录却无法获取当前用户的冲突问题

• Amplify Auth维护了两层校验逻辑：本地持久化缓存的登录状态标记、服务端实际有效session状态。你遇到的冲突是两层校验不同步导致的：本地残留了旧用户的登录标记，调用signIn时触发本地校验抛出「已存在登录用户」异常；但该标记对应的session实际已过期，调用getCurrentUser时校验session有效性失败，返回已登出提示。
• 原有代码存在逻辑漏洞：调用signOut时未强制清空本地所有缓存状态，且未确认状态完全清理完成就执行后续登录操作，容易残留无效状态。

1. 强制清理本地Auth缓存 #

调用signOut时传入全局登出配置，强制清空本地所有残留的Auth状态，避免状态不同步：

await Amplify.Auth.signOut(options: const SignOutOptions(globalSignOut: true));

2. 增加InvalidStateException异常的兼容逻辑 #

调用signIn时如果遇到该异常，先强制清理缓存，再重试一次登录操作。

3. 完整修改后的代码 #

signIn(String password, void Function(String, String) onSuccess,
      Future<void> Function(String) onFailure) async {
    AuthUser? currentUser;
    _isSignIn = false;

    try {
      currentUser = await Amplify.Auth.getCurrentUser();
      if (currentUser.username == _username) {
        _isSignIn = true;
      } else {
        // 强制全局登出，清空所有本地缓存
        await Amplify.Auth.signOut(options: const SignOutOptions(globalSignOut: true));
        // 增加短延迟等待状态同步，可适配低性能设备
        await Future.delayed(const Duration(milliseconds: 200));
      }
    } on Exception catch (e) {
      _isSignIn = false;
      // 无有效登录用户时也尝试清一次缓存，避免残留无效标记
      try {
        await Amplify.Auth.signOut(options: const SignOutOptions(globalSignOut: true));
      } catch (_) {}
    }

    try {
      SignInResult res;
      if (!_isSignIn) {
        try {
          res = await Amplify.Auth.signIn(
            username: _username,
            password: password,
          );
        } on InvalidStateException catch (_) {
          // 遇到状态异常先清缓存重试一次
          await Amplify.Auth.signOut(options: const SignOutOptions(globalSignOut: true));
          await Future.delayed(const Duration(milliseconds: 200));
          res = await Amplify.Auth.signIn(
            username: _username,
            password: password,
          );
        }
        if (res.isSignedIn) {
          _isSignIn = res.isSignedIn;
          currentUser = await Amplify.Auth.getCurrentUser();
        }
      }

      if (_isSignIn && currentUser != null) {
        List<AuthUserAttribute> attributes =
            await Amplify.Auth.fetchUserAttributes();

        onSuccess(
            currentUser.userId,
            attributes
                .firstWhere(
                    (attribute) => attribute.userAttributeKey == 'email')
                .value);

        _isEmailVerified = attributes
                .firstWhere((attribute) =>
                    attribute.userAttributeKey == 'email_verified')
                .value ==
            'true';
      }
    } on NotAuthorizedException catch (notAuthorizedException) {
      await onFailure(notAuthorizedException.message);
    } on AuthException catch (e) {
      print(e);
      try {
        await Amplify.Auth.getCurrentUser();
      } catch (_) {}
      await onFailure(e.message);
    }
  }

内容的提问来源于stack exchange，提问作者Ben