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Forum Discussion
tfrysinger
7 years agoExplorer | Level 4
Cancelling a file upload or download using Java 2 API
I have implemented a file upload and download capability in my Android app using the example approaches posted on GitHub. However, I need a way to interrupt the process to support the notion of 'canc...
Greg-DB
Dropbox Community Moderator
7 years agoWhen using the Dropbox API v2 Java SDK, you can cancel an in-progress upload by using the DbxUploader.abort method. That's available on its sub-classes for various use cases, such as UploadUploader, UploadSessionStartUploader, UploadSessionAppendV2Uploader, and UploadSessionFinishUploader.
For example, you can get the UploadUploader from upload or UploadBuilder.start (as opposed to directly chaining on uploadAndFinish).
That would look something like this: first, set up and save your uploader:
UploadUploader uploader = dbxClient.files().uploadBuilder(path)
.withMode(WriteMode.OVERWRITE)
.withClientModified(new Date(localFile.lastModified()))
.start();
Then, start the upload (maybe on another thread):
fileMetadata = uploader.uploadAndFinish(in, progressListener);
And if/when you need to cancel that upload:
if (someCondition) {
uploader.abort();
}
The DbxDownloader class doesn't offer an abort method, but you can use DbxDownloader.getInputStream to get an InputStream so you can more directly control if/when/how much data to read from it.
Hope this helps!
- tfrysinger7 years agoExplorer | Level 4
Hi - that helps a lot on the upload area.
For the download, I'm not sure I follow how getting a reference to the InputStream helps here. I suppose if I could read from it in "chunks" similar to upload, I could check every "chunk" to see if a cancel had been indicated, but I'm not sure how to do that.
Do you have a small code example to share?
Thanks!
- tfrysinger7 years agoExplorer | Level 4
Is something like this appropriate?
DbxDownloader<FileMetadata> downloader = dbxClient.files().downloadBuilder(dropboxPath + "/" + localFile) .start(); InputStream inputStream = downloader.getInputStream(); int count; long bytesWritten = 0; boolean keepGoin = true; byte data[] = new byte[WRITE_BUFFER]; while ( keepGoin && ((count = inputStream.read(data, 0, WRITE_BUFFER)) != -1)) { outputStream.write(data, 0, count); bytesWritten += count; progressListener.onProgress(bytesWritten); if ( listener != null ) { keepGoin = listener.cancelFileOperation(); } } if ( bytesWritten != size) { // Means we were interrupted throw new UserCancelException(InTouch.getInstance().getString(R.string.interrupted_exception_cancel_xfer)); }- Greg-DB7 years ago
Dropbox Community Moderator
Apologies I didn't have a code sample for that handy, but yes, what you just shared looks like what I had in mind.
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