Ionic 2 How to Download a file to local android storage from a url

Question

I need to create an android app to download a file when we give the url of the file and after press a button.I tried the steps on cordova file transfer page and also some stacks like Here but its not working. Here is my code for download in home.ts file

download() {
    this.presentToast('started');
    this.loader.present();

      const fileTransfer: FileTransferObject = this.transfer.create();

      const url = 'http://www.africau.edu/images/default/sample.pdf';

      fileTransfer.download(url, this.file.dataDirectory 
      +'file.pdf').then((entry) => {
        console.log('download complete: ' + entry.toURL());
        this.presentToast('download complete:' + entry.toURL());

        this.loader.dismiss();

      }, (error) => {
        // handle error
        this.presentToast(error);
        this.loader.dismiss();
      });

  }