Service in ionic 4 to provide method for downloading and opening a pdf file

pdf-viewer.service.ts

import { File } from "@ionic-native/file/ngx";
import { FileTransfer } from "@ionic-native/file-transfer/ngx";
import { FileOpener } from "@ionic-native/file-opener/ngx";
import { Injectable } from "@angular/core";

@Injectable({
  providedIn: "root"
})
export class PdfViewerService {
  fileTransfer: FileTransferObject;
  constructor(
    private fileOpener: FileOpener,
    private transfer: FileTransfer,
    private file: File
  ) {}

  download(url: string, title: string) {
    this.fileTransfer = this.transfer.create();
    this.fileTransfer
      .download(url, this.file.dataDirectory + title + ".pdf")
      .then(entry => {
        console.log("download complete: " + entry.toURL());
        this.fileOpener
          .open(entry.toURL(), "application/pdf")
          .then(() => console.log("File is opened"))
          .catch(e => console.log("Error opening file", e));
      });
  }
}