Load pdf stream and show it in ionic app.

documentViewer.ts

import {File} from '@ionic-native/file';
import { DocumentViewer } from '@ionic-native/document-viewer';

export class DocumentViewer
{
  constructor(private file : File, private documentViewer: DocumentViewer)
  {
  }

  public openDocument(document: Document)
  {
    if (!document)
    {
      this.showError("Document selected is null");
      return;
    }
    
    let path "documents/"+databaseId;
    let headers = new Headers({
    'Accept': 'application/pdf'
    });
    let options = new RequestOptions({headers, responseType: ResponseContentType.ArrayBuffer});
    let observableResponse = this.http.get(appConstants.apiUrl+
    path, options);

    observableResponse.subscribe((response: Response) => {
      this.showDocument(response, document);      
    }, (error: any) => {
      
    });
  }

  private showDocument(response: Response, document: Document)
  {
    let buffer = response.arrayBuffer();
    let pdfBlob = new Blob([buffer], {type: 'application/pdf'});
    this.file.writeFile(this.file.dataDirectory, document.databaseId+".pdf", pdfBlob, {replace: true}).then(c => {

      this.documentViewer.viewDocument(this.file.dataDirectory+document.databaseId+".pdf", "application/pdf",
        {print: {enabled: true}, bookmarks: {enabled: true}, email: {enabled: true}, title: document.title});
    });
  }
}