一，在controll重写add方法

/**
 * 添加
 */
public function add()
{
    if ($this->request->isPost()) {
        $params = $this->request->post("row/a");
        if ($params) {
            $params = $this->preExcludeFields($params);

            if ($this->dataLimit && $this->dataLimitFieldAutoFill) {
                $params[$this->dataLimitField] = $this->auth->id;
            }
            $result = false;
            Db::startTrans();
            try {
                //是否采用模型验证
                if ($this->modelValidate) {
                    $name = str_replace("\\model\\", "\\validate\\", get_class($this->model));
                    $validate = is_bool($this->modelValidate) ? ($this->modelSceneValidate ? $name . '.add' : $name) : $this->modelValidate;
                    $this->model->validateFailException(true)->validate($validate);
                }
                $result = $this->model->allowField(true)->save($params);
                Db::commit();
                //添加方法
                if($result){
                    //通过save后获取自增的ID，传进获取二维码方法，生成跳转指定小程序页面的二维码，保存到数据表中
                    $this->getEwm($this->model->getData('id'));
                }
            } catch (ValidateException $e) {
                Db::rollback();
                $this->error($e->getMessage());
            } catch (PDOException $e) {
                Db::rollback();
                $this->error($e->getMessage());
            } catch (Exception $e) {
                Db::rollback();
                $this->error($e->getMessage());
            }
            if ($result !== false) {
                $this->success();
            } else {
                $this->error(__('No rows were inserted'));
            }
        }
        $this->error(__('Parameter %s can not be empty', ''));
    }
    return $this->view->fetch();
}

2、自定义getEwm方法

   public function getEwm($id){
        $access_token = $this->getWxAccessToken();
//        p($access_token);die;
        //构建请求二维码参数
        //path是扫描二维码跳转的小程序路径，可以带参数?id=xxx
        //width是二维码宽度
        $qcode ="https://api.weixin.qq.com/cgi-bin/wxaapp/createwxaqrcode?access_token=".$access_token;

        $data = array();
        $data['scene'] =  'type=qrcode';
        $data['path'] = "pages/actDetails/actDetails?id=".$id;
        $data = json_encode($data);
//     $data = json_encode(array("path"=>"pages/index/index?aOpenid=".$openid,"width"=> 150));

        $jpg = $this->get_http_array($qcode,$data);
        $imgDir = 'uploads/zshd/';
//        $filename="ewm.jpg";///要生成的图片名字
        $filename = 'zshdact'.$id.'.jpg';
        $file = fopen("./".$imgDir.$filename,"w");//打开文件准备写入
        fwrite($file,$jpg);//写入
        fclose($file);//关闭

        $imgUrl = constant("URL").'/uploads/zshd/'.$filename;

//更新二维码图片到活动表中
        ZshdActivityModel::where('id',$id)->update(['ewmImage'=>$imgUrl]);
//        return json($imgUrl);
    }
    public function get_http_array($url,$post_data) {
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);   //没有这个会自动输出，不用print_r();也会在后面多个1
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
        $output = curl_exec($ch);

        return $output;
    }

    /**
     * 获取小程序access_token
     */
    public function getWxAccessToken(){
        $appId = constant('appidZshd');
        $appSecret = constant('secretZshd');
        $access_token = Cache::get('wx_access_token:'.$appId);
        if($access_token){
            return $access_token;
        }else{
            //1.请求url地址
            $url = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=".$appId."&secret=".$appSecret;
            $res = $this->curl($url);
            if(isset($res['errcode']) && $res['errcode']!=0){
                return ('获取access_token出错');
            }
            $access_token = $res['access_token'];

            Cache::set('wx_access_token:'.$appId,$access_token,5400);
            return $access_token;
        }
    }
    public function curl($url,$data = null){
//        p($data);die;
        $curl = curl_init();
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($curl, CURLOPT_TIMEOUT, 500);
        // 为保证第三方服务器与微信服务器之间数据传输的安全性，所有微信接口采用https方式调用，必须使用下面2行代码打开ssl安全校验。
        // 如果在部署过程中代码在此处验证失败，请到 http://curl.haxx.se/ca/cacert.pem 下载新的证书判别文件。
        curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
        curl_setopt($curl, CURLOPT_URL, $url);
        if (!empty($data)){
            curl_setopt($curl, CURLOPT_POST, 1);
//            curl_setopt($curl, CURLOPT_POSTFIELDS, http_build_query($data));
            curl_setopt($curl, CURLOPT_POSTFIELDS, $data);
        }

        $res = curl_exec($curl);
        curl_close($curl);
        $json_obj = json_decode($res,true);
//        p($json_obj);die;
        return $json_obj;
    }