Ionic file download not working

问题:

I am building an ionic app for wallpapers.

In the app,there is an image stored in www/assets/img displayed.I have build 2 buttons below,for downloading and retrieving the displayed image to the mobile device memory.

When i click download button,a dialog is shown,saying "Download Succeeded!Pug.jpg was successfully downloaded to: filepath".But when i check the phone memory no such file is there.Also when i click "Retrieve"Button it's showing dialog saying"File retrieval succeed!Pug.jpg was successfully retrieved from: filepath""even though file is not present in the phone memory.

This is home.ts code

import {Component} from '@angular/core';
import {NavController, Platform, AlertController} from 'ionic-angular';
import {Transfer, TransferObject} from '@ionic-native/transfer';
import {File} from '@ionic-native/file';

declare var cordova: any;

@Component({
  selector: 'page-home',
  templateUrl: 'home.html',
  providers: [Transfer, TransferObject, File]
})

export class HomePage {

  storageDirectory: string = '';

  constructor(public navCtrl: NavController, public platform: Platform, private transfer: Transfer, private file: File, public alertCtrl: AlertController) {
    this.platform.ready().then(() => {
      // make sure this is on a device, not an emulation (e.g. chrome tools device mode)
      if(!this.platform.is('cordova')) {
        return false;
      }

      if (this.platform.is('ios')) {
        this.storageDirectory = cordova.file.documentsDirectory;
      }
      else if(this.platform.is('android')) {
        this.storageDirectory = cordova.file.dataDirectory;
      }
      else {
        // exit otherwise, but you could add further types here e.g. Windows
        return false;
      }
    });
  }

  downloadImage(image) {

    this.platform.ready().then(() => {

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

      const imageLocation = `${cordova.file.applicationDirectory}www/assets/img/${image}`;

      fileTransfer.download(imageLocation, this.storageDirectory + image).then((entry) => {

        const alertSuccess = this.alertCtrl.create({
          title: `Download Succeeded!`,
          subTitle: `${image} was successfully downloaded to: ${entry.toURL()}`,
          buttons: ['Ok']
        });

        alertSuccess.present();

      }, (error) => {

        const alertFailure = this.alertCtrl.create({
          title: `Download Failed!`,
          subTitle: `${image} was not successfully downloaded. Error code: ${error.code}`,
          buttons: ['Ok']
        });

        alertFailure.present();

      });

    });

  }

  retrieveImage(image) {

    this.file.checkFile(this.storageDirectory, image)
      .then(() => {

        const alertSuccess = this.alertCtrl.create({
          title: `File retrieval Succeeded!`,
          subTitle: `${image} was successfully retrieved from: ${this.storageDirectory}`,
          buttons: ['Ok']
        });

        return alertSuccess.present();

      })
      .catch((err) => {

        const alertFailure = this.alertCtrl.create({
          title: `File retrieval Failed!`,
          subTitle: `${image} was not successfully retrieved. Error Code: ${err.code}`,
          buttons: ['Ok']
        });

        return alertFailure.present();

      });
  }

}

This is home.html code

<ion-header>
  <ion-navbar>
    <ion-title>
      File Transfer Example
    </ion-title>
  </ion-navbar>
</ion-header>

<ion-content padding>
  <ion-card>
    <ion-card-header>
      Ionic 3 File Transfer Example
    </ion-card-header>
    <ion-card-content>
      <img src="assets/img/pug.jpg" alt="Cute Pug">
      <button ion-button (click)="downloadImage('pug.jpg')" color="secondary">Download image</button>
      <button ion-button (click)="retrieveImage('pug.jpg')" color="secondary">Retrieve downloaded image</button>
    </ion-card-content>
  </ion-card>
</ion-content>

I build this ionic app based on this Github code example

I actually want the ionic app to first create a folder(app named folder) in internal memory and put all images there.So users can access files in that folder.For example,if app name is "Appsample" then all images should be in Appsample folder in internal memory.

How can i develop for above purpose?

Thanks.

回答1:

I just posted an answer to nearly the same question, see:

Download not working using filetransfer plugin.

The main problem here is that you are using the following directory to save your file:

 else if(this.platform.is('android')) {
        this.storageDirectory = cordova.file.dataDirectory;
 }

As stated in the cordova docs (https://cordova.apache.org/docs/en/latest/reference/cordova-plugin-file/#where-to-store-files), "cordova.file.dataDirectory" is the persistent and private data storage within the application's sandbox using internal memory.

Use cordova.file.externalDataDirectory to fit your purpose. Then the file should be placed somewhere here: "file:///storage/emulated/0/Android/data/subdomain.domainname.toplevdomain/files/...".

On Android, external storage directories always exist. If the device doesn't have a physical card, Android will emulate it.

回答2:

I Have the same issue when i wrote my download code it worked but i couldn't see the file on my phone

   1. Write download method
   2.  Write Permission method, Call Permission method
   3.  Call download method inside Permission, the phone will pop up and ask for permission for file read if it has not been set.
   4.  After download you might not be able to see where the file is on phone, you will now use photoViewer to view it on phone if it is 
image or use document viewer if it is pdf or other document related.

The plugins needed

private transfer: FileTransfer,
private fileTransfer: FileTransferObject,
private file: File,
private androidPermissions: AndroidPermissions,
private photoViewer: PhotoViewer,

getPermission() {
    // get permission from device to save 
    this.androidPermissions.checkPermission(this.androidPermissions.PERMISSION.READ_EXTERNAL_STORAGE).then(
        result =>//,
            err => this.androidPermissions.requestPermission(this.androidPermissions.PERMISSION.READ_EXTERNAL_STORAGE)
    );

    // get permission from device to save 
    this.androidPermissions.hasPermission(this.androidPermissions.PERMISSION.WRITE_EXTERNAL_STORAGE)
        .then(status => {
            if (status.hasPermission) {
                this.download('k');
            }
            else {
                this.androidPermissions.requestPermission(this.androidPermissions.PERMISSION.WRITE_EXTERNAL_STORAGE)
                    .then(status => {
                        if (status.hasPermission) {
                            this.download('');
                        }
                    });
            }
        });
}
public download() {
    let url = encodeURI(this.imgUrl);
    var imagePath = this.file.dataDirectory + "myDP.png";
    const fileTransfer = this.transfer.create();
    fileTransfer.download(url, imagePath).then((entry) => {
        this.generalProvider.showToast('download completed: ' + imagePath);
        this.photoViewer.show(entry.toURL());
    }, (error) => {
    });
}