如何将pdf文件从node / express app发送到Flutter应用程序？

Question

I have a nodejs code where I can download a pdf file since browser when I send 2 arguments in post request: fname and lname.

I am using express and pdfmake package in the backend.

const express = require('express');
const router = express.Router();

const pdfMake = require('../pdfmake/pdfmake');
const vfsFonts = require('../pdfmake/vfs_fonts');

pdfMake.vfs = vfsFonts.pdfMake.vfs;
router.post('/pdf', (req, res, next) => {
    //res.send('PDF');

    const fname = req.body.fname;
    const lname = req.body.lname;

    var documentDefinition = {
        content: [{
                image: 'data:image/png;base64 more code',
                width: 200,
                alignment: 'center'
            },
            { text: '\nGrupo de inspecciones predictivas', style: 'header', alignment: 'center' },
            { text: 'Reporte de inspección\n\n', style: 'subheader', alignment: 'center' },
            'El siguiente reporte tiene como objetivo describir los resultados encontrados a partir de la inspección en la fecha específica.',
            { text: 'Resumen del reporte', style: 'subheader' },
            {
                style: 'tableExample',
                table: {
                    widths: ['*', 'auto'],
                    body: [
                        ['Inspector:', { text: `${ fname }`, noWrap: true }],
                        ['Flota:', { text: '', noWrap: true }],
                        ['Número de flota:', { text: '', noWrap: true }],
                        ['Técnica:', { text: '', noWrap: true }],
                        ['Fecha de inicio:', { text: '', noWrap: true }],
                    ]
                }
            },
        ],
        styles: {
            header: {
                fontSize: 18,
                bold: true,
                margin: [0, 0, 0, 10]
            },
            subheader: {
                fontSize: 16,
                bold: true,
                margin: [0, 10, 0, 5]
            },
            tableExample: {
                margin: [0, 5, 0, 15]
            },
            tableHeader: {
                bold: true,
                fontSize: 13,
                color: 'black'
            }
        },
        defaultStyle: {
            // alignment: 'justify'
        }
    };

    const pdfDoc = pdfMake.createPdf(documentDefinition);
    pdfDoc.getBase64((data) => {
        res.writeHead(200, {
            'Content-Type': 'application/pdf',
            'Content-Disposition': 'attachment;filename="filename.pdf"'
        });

        const download = Buffer.from(data.toString('utf-8'), 'base64');
        res.end(download);
    });

});

However, as I mentioned above, this code apparently only return de pdf to browsers.

I need to download the pdf file to the Android/IOS storage in the Flutter app.

Answer 1

A good way to accomplish this would be to create a simple URL endpoint that returns the file directly. In your flutter app, you can use the file downloader to download the file directly to the app using something like this:

final taskId = await FlutterDownloader.enqueue(
  url: 'your download link',
  savedDir: 'the path of directory where you want to save downloaded files',
  showNotification: true, // show download progress in status bar (for Android)
  openFileFromNotification: true, // click on notification to open downloaded file (for Android)
);

You can find details on how to set up an endpoint for that here .

Answer 2

I have used google cloud platform to store the pdf generated by nodeJS. You can do it following the next articles: https://mzmuse.com/blog/how-to-upload-to-firebase-storage-in-node https://github.com/googleapis/google-cloud-node/issues/2334

    pdfDoc.getBase64((data) => {
        const keyFilename = "./myGoogleKey.json";
        const projectId = "my-name-project";
        const bucketName = `${projectId}.appspot.com`;
        var GoogleCloudStorage = require('@google-cloud/storage');

        const gcs = GoogleCloudStorage({
            projectId,
            keyFilename
        });

        const bucket = gcs.bucket(bucketName);
        const gcsname = 'reporte.pdf';
        const file = bucket.file(gcsname);
        var buff = Buffer.from(data.toString('utf-8'), 'base64');

        const stream = file.createWriteStream({
            metadata: {
                contentType: 'application/pdf'
            }
        });
        stream.on('error', (err) => {
            console.log(err);
        });
        stream.on('finish', () => {
            console.log(gcsname);
        });
        stream.end(buff);

        res.status(200).send('Succesfully.');
    });
});

This will generate a URL and you can follow the last answer given by Esh above.