错误下载:无法读取ionic4中未定义的属性‘TypeError’

Question

我正在尝试使用cordova-plugin- file -transfer下载pdf文件，但它捕获到以下错误"Cannot read property ' download‘of undefined“

app.module.ts导入：

import { File } from '@ionic-native/file/ngx';
import { FileTransfer } from '@ionic-native/file-transfer/ngx';

提供程序文件，FileTransfer

通过console.log，我检查到url工作正常，但下载方法不工作

let path = null;

if (this.plateform.is('ios')) {
  path = this.file.documentsDirectory;
} else {
  path = this.file.dataDirectory;
}

this.fileTransfer.download(url, path + 'file.pdf').then( data => {
 alert('download Complete');

Answer 1

用法：https://ionicframework.com/docs/native/file-transfer#usage

import { FileTransfer, FileUploadOptions, FileTransferObject } from '@ionic-native/file-transfer/ngx';
import { File } from '@ionic-native/file';

constructor(private transfer: FileTransfer, private file: File) { }

...

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

// Upload a file:
fileTransfer.upload(..).then(..).catch(..);

// Download a file:
fileTransfer.download(..).then(..).catch(..);

// Abort active transfer:
fileTransfer.abort();

// full example
upload() {
  let options: FileUploadOptions = {
     fileKey: 'file',
     fileName: 'name.jpg',
     headers: {}
     .....
  }

  fileTransfer.upload('<file path>', '<api endpoint>', options)
   .then((data) => {
     // success
   }, (err) => {
     // error
   })
}

download() {
  const url = 'http://www.example.com/file.pdf';
  fileTransfer.download(url, this.file.dataDirectory + 'file.pdf').then((entry) => {
    console.log('download complete: ' + entry.toURL());
  }, (error) => {
    // handle error
  });
}

Answer 2

您需要在使用前创建一个传输对象，即

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

transfer.download(url, path + 'file.pdf').then( data => {
 alert('download Complete');