How to get progress of a file being downloaded from google drive using REST API?

问题

I'm using this method to download a file from Google Drive.

My code:

        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        driveService.files().export(remoteFiles[0].getId(),"text/plain").executeMediaAndDownloadTo(byteArrayOutputStream);


        FileOutputStream fileOutputStream= new FileOutputStream(new File(downloadsDirectory,remoteFiles[0].getName()));


        byteArrayOutputStream.writeTo(fileOutputStream);

        byteArrayOutputStream.flush();

        byteArrayOutputStream.close();
        fileOutputStream.close();

Is there a way to get the progress of the file download?

回答1:

Answering my own question,found it on this page.

//custom listener for download progress
class DownloadProgressListener implements MediaHttpDownloaderProgressListener{


    @Override
    public void progressChanged(MediaHttpDownloader downloader) throws IOException {
        switch (downloader.getDownloadState()){

            //Called when file is still downloading
            //ONLY CALLED AFTER A CHUNK HAS DOWNLOADED,SO SET APPROPRIATE CHUNK SIZE
            case MEDIA_IN_PROGRESS:
                //Add code for showing progress
                break;
            //Called after download is complete
            case MEDIA_COMPLETE:
                //Add code for download completion
                break;
         }
    }
}


//create a Drive.Files.Get object,
//set a ProgressListener
//change chunksize(default chunksize seems absurdly high)
Drive.Files.Get request = driveService.files().get(remoteFiles[0].getId());
request.getMediaHttpDownloader().setProgressListener(new DownloadProgressListener()).setChunkSize(1000000);
request.executeMediaAndDownloadTo(outputStream);

回答2:

The first thing that I can think of is wrapping the FileOutputStream in a custom Stream that overrides the write method to additionally notify a listener for the amount of bytes written. Like this:

public class ProgressOutputStream extends OutputStream {
    IProgressListener _listener;
    OutputStream _stream;
    int _position;

    public ProgressOutputStream(OutputStream stream, IProgressListener listener) {
        _stream = stream;
        _listener = listener;
    }

    @Override
    public void write(byte[] b, int offset, int len) {
        _stream.write(b, offset, len);
        _position += len;
        reportProgress();
    }

    private void reportProgress() {
        _listener.onProgressUpdate(_position);
    }

    @Override
    public void write(int b) {
        _stream.write(b);
    }
}

interface IProgressListener {
    void onProgressUpdate(int progress);
}

The rest is to know the size of the file so that you can calculate the progress in percentages in your progress listener.

来源：https://stackoverflow.com/questions/39369580/how-to-get-progress-of-a-file-being-downloaded-from-google-drive-using-rest-api