Ionic and jsPDF , using FILE Transfer to download pdf not working

Hello guys, i want to use jsPDF library with IONIC3 to download PDF , i have created a simple document and when i try to download it with the default function from jsPDF doc.Save() it work in my browser , but in a real device won’t work.
So i decided to use FileTransfer Plugins from IONIC native , i have firstly created a blob File from jsPDF output , then i tried to use the writeFile() function from IONIC FILE plugin to create a new file from the blob , then i tried to download that file using Download() function from FileTransfer , Here is my code :

    const fileTransfer: FileTransferObject = this.transfer.create();
    //Initialize jsPdf
    let doc = new jsPDF();
    doc.text('Testing PDFs', 20, 20);
    //"example.pdf") This is the default way to download pdf In jsPDF , but it's not working in ionic
    // So Here i create new File from the blob
    let blob = doc.output('blob', {type: 'application/pdf'});
              console.log("File created successfly" + value);
              // if The file successfuly created , i want to download it
     this.file.dataDirectory+"example.pdf" ,this.file.dataDirectory+"example.pdf")
                  console.log("Download Success : " , entry);
                      console.log("Error when downloading file : " ,error);
      console.log("Error creating File");


if i look to my output console everything work ok , but nothing Happen !!

[19:50:26] console.log: File created successfly{“isFile”:true,“isDirectory”:false,“name”:“example.pdf”,“fullPath”:"/example.pdf",“filesystem”:"<FileSystem:

[19:50:26] console.log: Download Success :

Look at this solution =>
it work for me using FileOpener