[GitHub] [cordova-plugin-file-transfer] the-other-sunny opened a new issue, #374: `download` method failing on cordova / android platform with `java.lang.NullPointerException` error.

[via GitHub]

the-other-sunny opened a new issue, #374:
URL: https://github.com/apache/cordova-plugin-file-transfer/issues/374

   Hi !
   I'm currently unable to make the plugin work properly.
   `FileTransfer.download` is failing with an error code 3 
(`FileTransferError.CONNECTION_ERR`) and an exception 
`java.lang.NullPointerException`.
   
   ## Minimal example
   
   ```sh
   cordova create . com.example.my_app "My App"
   cordova platform add android
   cordova plugin add cordova-plugin-file-transfer
   ```
   
   Add this child to the `widget` element in `config.xml`.
   
   ```xml
   <access origin="*" />
   ```
   
   Add a call to the `demo` function below from within `onDeviceReady`.
   
   ```js
   function demo() {
       window.requestFileSystem(window.PERSISTENT, 5 * 1024 * 1024,
           fs => fs.root.getFile('cordova_bot.png', { create: true, exclusive: 
false },
               fileEntry => ft_approach(fileEntry),
               error => console.log(`file creation error: ${error}`)
           ),
           (error) => console.log(`fs loading error: ${error}`)
       );
   }
   
   function ft_approach(fileEntry) {
       const fileTransfer = new FileTransfer();
       
       fileTransfer.download(
           'https://cordova.apache.org/static/img/cordova_bot.png',
           fileEntry.toURL(),
           () => window.alert('download complete'),
           error => console.log(`download error: ${JSON.stringify(error, 
undefined, 2)}`),
           false,
       );
   }
   ```
   
   Run the app on the Android Studio `emulator` and attach Chrome DevTools . 
   The output should be something like:
   
   ```
   download error: {
     "code": 3,
     "source": "https://cordova.apache.org/static/img/cordova_bot.png";,
     "target": "https://localhost/__cdvfile_persistent__/cordova_bot.png";,
     "http_status": 200,
     "body": null,
     "exception": "java.lang.NullPointerException"
   }
   ```
   
   ## Workaround
   
   Using web APIs.
   Replacing `ft_approach` with the `xhr_approach` function below works, 
although not idea for large files.
   
   ```js
   function xhr_approach(fileEntry) {
       const xhr = new XMLHttpRequest();
   
       xhr.open('GET', 'https://cordova.apache.org/static/img/cordova_bot.png', 
true);
       xhr.responseType = 'blob';
       xhr.onload = function () {
           const blob = xhr.response;
           if (xhr.status != 200) {
               console.error(`request error ${xhr.status}: ${xhr.statusText}`);
               return;
           }
           fileEntry.createWriter(function (fileWriter) {
               fileWriter.onwriteend = () => window.alert('download complete');
               fileWriter.onerror = error => console.log(`file writing error: 
${error}`);
               fileWriter.write(blob);
           });
       };
       xhr.onerror = function() {
           console.log('request error')
       }
       xhr.send();
   }
   ```
   
   ## Versions
   
   ```
   Windows 10 Home
   Node 18.17.1
   Cordova 12.0.0
   cordova-android 12.0.1
   cordova-plugin-file 8.0.0
   cordova-plugin-file-transfer 2.0.0
   Android SDK 33
   Gradle 8.3
   ```


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