如果你同时导入"dart:io"和"dart:html"，它不知道要导入哪个平台并给出错误。导入其中一个。

import 'dart:io';
Platform.isIOS ? CupertinoWidget() : MaterialWidget()

最“扑”的答案如下:

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

//...

if(Theme.of(context).platform == TargetPlatform.android)
    //do sth for Android
else if(Theme.of(context).platform == TargetPlatform.iOS)
    //do sth else for iOS
else if(Theme.of(context).platform == TargetPlatform.fuchsia)
    //even do sth else for Fuchsia OS

import 'dart:io' show Platform;

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

所有选项包括:

Platform.isAndroid
Platform.isFuchsia
Platform.isIOS
Platform.isLinux
Platform.isMacOS
Platform.isWindows

你也可以使用kIsWeb来检测你是否在web上运行，kIsWeb是一个全局常量，指示应用程序是否被编译为在web上运行:

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.
}

平台文档:https://api.flutter.dev/flutter/dart-io/Platform-class.html kIsWeb文档:https://api.flutter.dev/flutter/foundation/kIsWeb-constant.html

**multiple platform you check and run your code according specific platform **

bool isIOS = Theme.of(context).platform == TargetPlatform.iOS;
bool isAndroid = Theme.of(context).platform == TargetPlatform.android;
bool islinux = Theme.of(context).platform == TargetPlatform.linux;
bool isfuchsia = Theme.of(context).platform == TargetPlatform.fuchsia;
bool isMacOS = Theme.of(context).platform == TargetPlatform.macOS;
bool iswindows = Theme.of(context).platform == TargetPlatform.windows;

为更简单的方式为网络和应用程序。试试这个

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


var platformName = '';
if (kIsWeb) {
  platformName = "Web";
} else {
  if (Platform.isAndroid) {
    platformName = "Android";
  } else if (Platform.isIOS) {
    platformName = "IOS";
  } else if (Platform.isFuchsia) {
    platformName = "Fuchsia";
  } else if (Platform.isLinux) {
    platformName = "Linux";
  } else if (Platform.isMacOS) {
    platformName = "MacOS";
  } else if (Platform.isWindows) {
    platformName = "Windows";
  }
}
print("platformName :- "+platformName.toString());

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