How to start a download in Magento 2?

Question

I have following code:

<?php
namespace UV\Bestellung\Controller\Adminhtml\Index;

use Magento\Framework\App\Action\Action;
use Magento\Framework\Controller\ResultFactory;

class Index extends Action
{

    public function generateBestellschein() {
        $pdf = new Zend("Bestellschein.pdf");

        return $pdf;
    }

    public function execute()
    {
        return generateBestellschein();
    }
}

I am creating a PDF via

generateBestellschein();

and

execute();

is executed when custom button is clicked. I want it to start a download of the PDF.

How do I do that?

Answer 1

Sample code for download file.

you can create your controller action by extending \Magento\Backend\App\Action for backend or \Magento\Framework\App\Action\Action for frontend.
and make it look like this:

<?php 
namespace Your\Namespace\Here;

class ClassName extends \Magento\Backend\App\Action 
{
    public function __construct(
        \Magento\Framework\Controller\Result\RawFactory $resultRawFactory,
        \Magento\Framework\App\Response\Http\FileFactory $fileFactory,
        \Magento\Backend\App\Action\Context $context
    ) {
        $this->resultRawFactory      = $resultRawFactory;
        $this->fileFactory           = $fileFactory;
        parent::__construct($context);
    }
    public function execute()
    {
        //do your custom stuff here
        $fileName = 'file name for download here';
        $this->fileFactory->create(
            $fileName,
            null, //content here. it can be null and set later 
            base dir of the file to download here
            'application/octet-stream', //content type here
            content lenght here...can be null
        );
        $resultRaw = $this->resultRawFactory->create();
        $resultRaw->setContents(contents of file here); //set content for download file here
        return $resultRaw;
    }
}

Answer 2

Should see good examples:

vendor/magento/module-sales/Controller/Adminhtml/Order/Pdfinvoices.php
vendor/magento/module-sales/Controller/Adminhtml/Order/Pdfshipments.php

We should use \Magento\Framework\App\Response\Http\FileFactory to declare headers and content file in response for file download.

But, the Pdf content renderer is not easy. You should take a look at some existing code lines. You can use some PDF libraries.