感谢科林，最终答案是:

bool isIOS = Theme.of(context).platform == TargetPlatform.iOS;

if (Platform.isAndroid) {
  // Android-specific code/UI Component
} else if (Platform.isIOS) {
  // iOS-specific code/UI Component
}

不要忘记导入IO库。

import 'dart:io';

如果你使用导入'dart:html';那么你必须指定平台定义，因为两个库都有“平台”的定义

在这种情况下，使用如下所示的平台特定代码:

import 'dart:io' as IO;
import 'dart:html';

if (IO.Platform.isAndroid) {
  // Android-specific code/UI Component
} else if (IO.Platform.isIOS) {
  // iOS-specific code/UI Component
}

如果你正在寻找合适的平台集成，我建议在Flutter网站上使用完整的示例: https://flutter.dev/docs/development/platform-integration/platform-channels

您可以使用通用平台包:

https://pub.dev/packages/universal_platform

import 'package:universal_platform/universal_platform.dart';

bool isIos = UniversalPlatform.isIOS;
bool isAndroid = UniversalPlatform.isAndroid;
bool isWeb = UniversalPlatform.isWeb;
print('iOS: $isIos');
print('Android: $isAndroid');
print('Web: $isWeb');

所以这里有一个小工具，我用来检测平台和操作系统的反应适当。

import'dart:io' show Platform;
import 'package:flutter/foundation.dart' show kIsWeb;

class Util {

  os getPlatform() {
    if (kIsWeb) {
      return os.Web;
    } else if (Platform.isIOS) {
      return os.IOS;
    } else if (Platform.isAndroid) {
      return os.Android;
    } else if (Platform.isFuchsia) {
      return os.Fuchsia;
    } else if (Platform.isLinux) {
      return os.Linux;
    } else if (Platform.isMacOS) {
      return os.MacOS;
    } else if (Platform.isWindows) {
      return os.Windows;
    }
    return os.Unknown;
  }

  bool isWeb() {
    return (getPlatform()==os.Web);
  }

  bool isMobile() {
    os platform = getPlatform();
    return (platform == os.Android || platform == os.IOS || platform== os.Fuchsia);
  }

  bool isComputer() {
    os platform = getPlatform();
    return (platform == os.Linux || platform == os.MacOS || platform== os.Windows);
  }

}

enum os { Unknown, Web, Android, Fuchsia, IOS, Linux, MacOS, Windows }

import 'dart:io' show Platform;

if (Platform.isAndroid) {
  // Android-specific code
} else if (Platform.isIOS) {
  // iOS-specific code
}else if (Platform.isFuchsia) {
  // Fuchsia-specific code
}else if (Platform.isLinux) {
  // Linux-specific code
}else if (Platform.isMacOS) {
  // MacOS-specific code
}else if (Platform.isWindows) {
  // Windows-specific code
}else if (Platform.isWindows) {
  // Windows-specific code
}

网络

import 'package:flutter/foundation.dart' show kIsWeb;

if (kIsWeb) {
  // running on the web!
} else {
  // NOT running on the web! You can check for additional platforms here.
}

import 'dart:io' show Platform;  //at the top

String os = Platform.operatingSystem; //in your code
print(os);