你可以通过使用像这样的onProgress函数来显示progressBar

You can show progressBar by using onProgress function like this

public   fileTransfer: TransferObject = this.transfer.create();
public upload(path,folder) 
{
  url="http://www.axmag.com/download/pdfurl-guide.pdf";
  var trustHosts = true;
  this.presentLoading("Loading");
  //**Progress Bar**
  this.fileTransfer.onProgress((e)=>
  {
    let prg=(e.lengthComputable) ?  Math.round(e.loaded / e.total * 100) : -1;  
    console.log("progress:"+prg);
  });

  this.fileTransfer.upload(file_path, api_endpoint, options, data).then((entry) => {
//handle success        
console.log('upload complete: ' );
  },
  (error) => {
    this.loader.dismiss();
    alert('uploading faild: ');
    console.log(error);
  //handle error
  });
}

现在你可以调用upload（）函数来上传文件

Now you can call upload() function to upload a file