//文章模型关联用户

    public function user(){

        return $this->belongsTo(User::class, 'user_id', 'id');

    }

//ExcelExporter.php

<?php

namespace App\Admin\Extensions;

use Encore\Admin\Grid;

use Encore\Admin\Grid\Exporters\AbstractExporter;

use Maatwebsite\Excel\Facades\Excel;

class ExcelExpoter extends AbstractExporter

{

    protected $head = [];

    protected $body = [];

    public function setAttr($head, $body){

        $this->head = $head;

        $this->body = $body;

    }

    public function export()

    {

        Excel::create('Filename', function($excel) {

            $excel->sheet('Sheetname', function($sheet) {

                // 这段逻辑是从表格数据中取出需要导出的字段

                $head = $this->head;

                $body = $this->body;

                $bodyRows = collect($this->getData())->map(function ($item)use($body) {

                    foreach ($body as $keyName){

                        $arr[] = array_get($item, $keyName);

                    }

                    return $arr;

                });

                $rows = collect([$head])->merge($bodyRows);

                $sheet->rows($rows);

            });

        })->export('xls');

    }

}

            $excel = new ExcelExpoter();

            $excel->setAttr(['id', '标题', '作者'], ['id', 'title', 'user.username']);

            $grid->exporter($excel);