在哪里生成Firebase数据库数据的PDF移动应用程序，或Firebase托管web应用程序

Question

我有一个Android应用程序和一个网络应用程序（托管在Firebase Hosting上）。Android 应用会生成数据并将其保存到 Firebase 实时数据库中。Android 应用和 Web 应用都可以查看数据。

从Firebase数据库生成数据PDF的最佳位置是哪里——Android应用程序还是Web应用程序（通过JavaScript，例如jsPDF）？它将保存在Firebase存储中。

我以为Android应用程序可以调用后端来生成PDF，并且PDF的链接将被发送回Android应用程序。但是，Firebase是一种无服务器架构，因此似乎最好的解决方案是在Android应用程序上创建PDF，然后将其上传到Firebase Storage...？

Answer 1

由于有Firebase Functions（Firebase简介），您可以使用NodeJS创建PDfs，例如使用pdfkit（PDFKit）。下面的示例描述了在Account tCreation（事件）上生成PDF、将其保存到存储并通过邮件发送给用户的方法。所有这些都发生在Firebase服务器上。对于所有使用过的Librarys，不要忘记npm安装它们并将它们包含到package.json.一个棘手的部分是将Firebase Admin SDK添加到您的服务器。此外，这也很有帮助。

const functions = require('firebase-functions');
const admin = require("firebase-admin");

const nodemailer = require('nodemailer');
const pdfkit = require('pdfkit');

const gmailEmail = '[e-mail]'
const gmailPassword = 'test123.ThisisNoTSave'
const mailTransport = nodemailer.createTransport( `smtps://${gmailEmail}:${gmailPassword}@smtp.gmail.com`);

const serviceAccount = require("./youradminsdk.json");
//Save this file to your functions Project

// Your company name to include in the emails
const APP_NAME = 'My App';
const PROJECT_ID = "google-testproject";

admin.initializeApp({
    credential: admin.credential.cert(serviceAccount),
    databaseURL: `https://${PROJECT_ID}.firebaseio.com`,
    storageBucket: `${PROJECT_ID}.appspot.com`
});

var config = {
    projectId: `${PROJECT_ID}`,
    keyFilename: './youradminsdk.json'
};

const storage = require('@google-cloud/storage')( config);
const datastore= require('@google-cloud/datastore')(config);

// [START onCreateTrigger]
exports.sendPDFMail = functions.auth.user().onCreate(event => {
// [END onCreateTrigger]

       // [START eventAttributes]
       const doc = new pdfkit;
       const user = event.data; // The Firebase user.
       const email = user.email; // The email of the user.
       const displayName = user.displayName; // The display name of the user.
       // [END eventAttributes]

       const bucket = storage.bucket(`${PROJECT_ID}.appspot.com`); 
       console.log(bucket);
       const filename =  Date.now() + 'output.pdf';                       
       const file = bucket.file(filename);
       const stream = file.createWriteStream({resumable: false});

      // Pipe its output to the bucket
       doc.pipe(stream);              
       doc.fontSize(25).text('Some text with an embedded font!', 100, 100);           
       doc.end();        
       stream.on('finish', function () {                   
             return sendPDFMail(email, displayName, doc);
       });

       stream.on('error', function(err) {
            console.log(err);
       });        
      })
    ;
    // [END sendPDFMail]


    // Sends a welcome email to the given user.
    function sendPDFMail(email, displayName, doc) {
        const mailOptions = {
            from: '"MyCompany" <[e-mail]>',
            to: email,        
        };

        mailOptions.subject = `Welcome to ${APP_NAME}!`;
        mailOptions.text = `Hey ${displayName}!, Welcome to ${APP_NAME}. I hope you will enjoy our service.`;
        mailOptions.attachments =  [{filename: 'meinPdf.pdf', content: doc, contentType: 'application/pdf'  }];        

        return mailTransport.sendMail(mailOptions).then(() => {
            console.log('New welcome email sent to:', email);
        });
    }