开放标签<wx-open-launch-app>中的冷启动extinfo数据获取不到？

- (void)onReq:(BaseReq*)req 
{
    //获取开放标签传递的extinfo数据逻辑
	if ([req isKindOfClass:[LaunchFromWXReq class]]) 
	{
		WXMediaMessage *msg = req.message;
		NSString *openID = req.openID;
		NSString *extinfo = req.msg.messageExt;
		// handle...
	}
}io