平台精确的代码和访问本地API。在Windows的情况下，您可以使用Win32 API来获取有关活动窗口及其进程ID的统计信息。为此，您可以使用Dart的FFI（外部函数接口）来命名来自动态超链接库（DLL）的功能，如user32.Dll和psapi.Dll。
这里有一个例子

import 'dart:ffi' as ffi;

class Psapi {
  static final ffi.DynamicLibrary psapi = ffi.DynamicLibrary.open('psapi.dll');

  static int GetWindowThreadProcessId(
      ffi.IntPtr hwnd, ffi.Pointer<ffi.Uint32> lpdwProcessId) {
    return psapi
        .lookupFunction<
            ffi.Uint32 Function(
                ffi.IntPtr hwnd, ffi.Pointer<ffi.Uint32> lpdwProcessId),
            int Function(ffi.IntPtr hwnd,
                ffi.Pointer<ffi.Uint32> lpdwProcessId)>('GetWindowThreadProcessId')(
      hwnd,
      lpdwProcessId,
    );
  }
}

class User32 {
  static final ffi.DynamicLibrary user32 = ffi.DynamicLibrary.open('user32.dll');

  static ffi.IntPtr GetForegroundWindow() {
    return user32
        .lookupFunction<ffi.IntPtr Function(), ffi.IntPtr Function()>(
            'GetForegroundWindow')();
  }
}

void main() {
  ffi.Pointer<ffi.Uint32> pidPointer = ffi.allocate<ffi.Uint32>();
  ffi.IntPtr hwnd = User32.GetForegroundWindow();

  Psapi.GetWindowThreadProcessId(hwnd, pidPointer);

  int pid = pidPointer.value;

  print('Process ID of the active window: $pid');

  ffi.free(pidPointer);
}

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我终于找到了解决办法。

import 'dart:ffi' as ffi;
import 'package:ffi/ffi.dart';
import 'package:win32/win32.dart';

void main() {
    ffi.Pointer<ffi.Uint32> pidPointer = calloc();
    int hwnd = GetForegroundWindow();

    GetWindowThreadProcessId(hwnd, pidPointer);

    int pid = pidPointer.value;

    print('Process ID of the active window: $pid');
    free(pidPointer);
}

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