Saving a file into phone

Ionic Framework ionic-v3
1

I’m new with ionic. trying build a simple app. App needs to download a video than play it. Here is my codes. What is wrong with it?


async indirOynat(){
   
      this.file.checkFile(this.file.dataDirectory, 'vidyo.mp4').then(_ => this.sadeceoynat()).catch(err => this.indir());
 
 
}
indir()
{
   
   let alert = this.alertCtrl.create({
    title: 'UYARI',
    subTitle: "1 mb'lık bir video telefonunuza indirilecektir.",
    buttons: ['TAMAM']
     });
      alert.present();

  const url = 'http://www.sample-videos.com/video/mp4/720/big_buck_bunny_720p_1mb.mp4';
    const fileTransfer: TransferObject = this.transfer.create();
  fileTransfer.download(url, this.file.dataDirectory + 'vidyo.mp4').then((entry) => {
     this.videoOption ={
  volume : 0.7
}
 
this.vp.play(this.file.dataDirectory + 'vidyo.mp4',this.videoOption);
  }, (error) => {
    // handle error
  });
}
sadeceoynat()
{
   let alert = this.alertCtrl.create({
    title: 'UYARI',
    subTitle: "bu dosya telefonunuzda mevcut, indirmeden oynatılacaktır.",
    buttons: ['TAMAM']
     });
      alert.present();

  this.videoOption ={
  volume : 0.7
}
 
this.vp.play(this.file.dataDirectory + 'vidyo.mp4',this.videoOption);
}

and also it works too slow.