最近刚好有个功能，需要这个逻辑，话不多说，上代码。

struct handle_data {
	unsigned long process_id;
	HWND best_handle;
};

BOOL IsMainWindow(HWND handle)
{   
	return GetWindow(handle, GW_OWNER) == (HWND)0 && IsWindowVisible(handle);
}


HWND FindMainWindow(unsigned long process_id)
{
	handle_data data;
	data.process_id = process_id;
	data.best_handle = 0;
	EnumWindows(EnumWindowsCallback, (LPARAM)&data);
	return data.best_handle;
}

BOOL CALLBACK EnumWindowsCallback(HWND handle, LPARAM lParam)
{
	handle_data& data = *(handle_data*)lParam;
	unsigned long process_id = 0;
	GetWindowThreadProcessId(handle, &process_id);
	if (data.process_id != process_id || !IsMainWindow(handle)) {
		return TRUE;
	}
	data.best_handle = handle;
	return FALSE;   
}

然后main函数，这样调用即可，

HWND hwnd = FindMainWindow(uProcessID);

这个uProcessID就是任务管理器里PID一列的内容，你也可以写个函数用进程名来获取。