Generated PDF invalid file format when opening on android

Question

I am using Ionic 4, Capacitor and pdfMake to generate a pdf and open on an android emulator. Since the Capacitor file write does not support blob I am sending it as base64.

Note: I tried using a Cordova plugin to save as a blob but it doesn't work properly with capacitor. Also I have the solution working fine in a Cordova only project but I need to use Capacitor.

However when I open the pdf on the device it says it is in an invalid format. Any ideas what I am doing wrong here?

if (this.plt.is('cordova')) {
  this.pdfObj.getBase64((data) => {
    this.pdfBase64 = data;
    console.log(this.pdfBase64);
  });


downloadPdf() {
const { Filesystem } = Plugins;

if (this.plt.is('cordova')) {
  console.log('3');
    // Save the PDF to the data Directory of our App
    const fileName = 'defectreport.pdf';
    try {
      Filesystem.writeFile({
        path: fileName,
        data: this.pdfBase64,
        directory: FilesystemDirectory.Data,
        encoding: FilesystemEncoding.ASCII
      }).then((writeFileResult) => {
        console.log('File Written');
        Filesystem.getUri({
            directory: FilesystemDirectory.Data,
            path: fileName
        }).then((getUriResult) => {
            console.log(getUriResult);
            const path = getUriResult.uri;
            this.fileOpener.open(path, 'application/pdf')
            .then(() => console.log('File is opened'))
            .catch(error => console.log('Error openening file', error));
        }, (error) => {
            console.log(error);
        });
      });
      console.log('writeFile complete');
    } catch (error) {
      console.error('Unable to write file', error);
    }

Answer 1

The documentation for the Capacitor fileSystem is misleading. If you pass the encoding parameter to Filesystem.writeFile it assumes that it is a plain text file. If you do not provide it it assumes base64. The code below works.

 Filesystem.writeFile({
        path: fileName,
        data: this.pdfBase64,
        directory: FilesystemDirectory.Documents