Java-在Google云端硬盘上下载和删除文件

Question

I have an Android app that at some point, needs to create and delete some text files on Google Drive as well as download / grab the content of those files to display it in an activity. So I've been trying for some time to find a way to do this using only the file's name but I seem to be having a lot of problem finding some info on how to do it. Moreover, not being a Java dev does not make things easier.

I managed to create a file inside the root folder:

private void createFile()
{
    println("CreateFileActivity > createFile");

    final Task<DriveFolder> rootFolderTask = getDriveResourceClient().getRootFolder();
    final Task<DriveContents> createContentsTask = getDriveResourceClient().createContents();
    Tasks.whenAll(rootFolderTask, createContentsTask)
            .continueWithTask(task -> {
                DriveFolder parent = rootFolderTask.getResult();
                DriveContents contents = createContentsTask.getResult();
                OutputStream outputStream = contents.getOutputStream();

                try (Writer writer = new OutputStreamWriter(outputStream))
                {
                    writer.write("SOME_TEXT_HERE");
                }

                MetadataChangeSet changeSet = new MetadataChangeSet.Builder()
                                                      .setTitle("MyFile.txt")
                                                      .setMimeType("text/plain")
                                                      .setStarred(true)
                                                      .build();

                return getDriveResourceClient().createFile(parent, changeSet, contents);
            })
            .addOnSuccessListener(this,
                    driveFile -> {
                        System.out.println("File created");

                        Intent resultActvityIntent = new Intent(getApplicationContext(), ResultActivity.class);
                        startActivity(resultActvityIntent);
                    })
            .addOnFailureListener(this, e -> {
                Toast.makeText(this, "Unable to create file", Toast.LENGTH_SHORT).show();
                System.out.println("Unable to create file");
                Log.e(TAG, "Unable to create file", e);

                Intent resultActvityIntent = new Intent(getApplicationContext(), ResultActivity.class);
                startActivity(resultActvityIntent);
            });
}

To my surprise however, it creates a new file with the same name every time instead of overwriting it.

Also, I cannot seem to be able to delete the file or download it / grad the content using only the file name. I found a lot of info on how to delete the file using the file ID and I also found an example provided by Google but it's not really what I need.

@Override
protected void onDriveClientReady() 
{
    pickTextFile()
            .addOnSuccessListener(this,
                    driveId -> deleteFile(driveId.asDriveFile()))
            .addOnFailureListener(this, e -> {
                Log.e(TAG, "No file selected", e);
                showMessage(getString(R.string.file_not_selected));
                finish();
            });
}
private void deleteFile(DriveFile file) 
{
    // [START delete_file]
    getDriveResourceClient()
            .delete(file)
            .addOnSuccessListener(this,
                    aVoid -> {
                        showMessage(getString(R.string.file_deleted));
                        finish();
                    })
            .addOnFailureListener(this, e -> {
                Log.e(TAG, "Unable to delete file", e);
                showMessage(getString(R.string.delete_failed));
                finish();
            });
    // [END delete_file]
}

Any ideas on how to do this or where to start looking? Or it's not possible to delete the file directly from within an app?

Answer 1

This is how the Google drive API works. Everything uses the file id. What you should be doing is a file.list sending the q parameters to search for files with the correct name and file type. You will then have the file id to be able to update the file.

Google drive API doesn't prevent you from creating more than one file with the same name.

Answer 2

Following @DalmTo's suggestion, here's my solution for deleting a file on Google Drive. The example below skips trash and deletes the file permanently.

private static final String fileName = "MyAppsTextFile.txt";

private void deleteExistingFile()
{
    println("DeleteFileActivity > deleteExistingFile");

    Query query = new Query.Builder()
            .addFilter(Filters.eq(SearchableField.TITLE, fileName))
            .build();

    Task<MetadataBuffer> queryTask = getDriveResourceClient().query(query);

    queryTask.addOnSuccessListener( this,
            new OnSuccessListener<MetadataBuffer>()
            {
                @Override
                public void onSuccess(MetadataBuffer metadataBuffer)
                {
                    System.out.println("Success. File/s found!");

                    for(Metadata m : metadataBuffer)
                    {
                        DriveResource driveResource = m.getDriveId().asDriveResource();

                        System.out.println("Deleting file " + fileName + " with DriveID m.getDriveId()");
                        getDriveResourceClient().delete(driveResource);
                    }
                }
            })
            .addOnFailureListener(this, new OnFailureListener()
            {
                @Override
                public void onFailure(@NonNull Exception e)
                {
                    System.out.println("ERROR: File not found!");
                }
            });
}

And since the thread title is Download and Delete, here's the code to get the file content from Google drive:

private static final String fileName = "MyAppsTextFile.txt";

private void getFiles()
{
    System.out.println("GetGoogleDriveFile > getFiles");

    Query query = new Query.Builder()
            .addFilter(Filters.eq(SearchableField.TITLE, fileName))
            .build();

    Task<MetadataBuffer> queryTask = getDriveResourceClient().query(query);

    queryTask
            .addOnSuccessListener(this,
                    new OnSuccessListener<MetadataBuffer>()
                    {
                        @Override
                        public void onSuccess(MetadataBuffer metadataBuffer)
                        {
                            System.out.println("On SUCCESS");

                            for( Metadata m : metadataBuffer )
                            {
                                DriveFile driveFile = m.getDriveId().asDriveFile();
                                getFileContents(driveFile);
                            }
                        }
                    })
            .addOnFailureListener(this, new OnFailureListener()
            {
                @Override
                public void onFailure(@NonNull Exception e)
                {
                    System.out.println("On FAILURE");
                }
            });
}

private void getFileContents(DriveFile myFile)
{
    System.out.println("GetGoogleDriveFile > getFileContents");

    Task<DriveContents> openFileTask =
            getDriveResourceClient().openFile(myFile, DriveFile.MODE_READ_ONLY);

    openFileTask
            .continueWithTask(new Continuation<DriveContents, Task<Void>>()
            {
                @Override
                public Task<Void> then(@NonNull Task<DriveContents> task) throws Exception
                {
                    DriveContents contents = task.getResult();

                    try (BufferedReader reader = new BufferedReader(
                            new InputStreamReader(contents.getInputStream())))
                    {
                        StringBuilder builder = new StringBuilder();
                        String line;

                        while ((line = reader.readLine()) != null)
                        {
                            builder.append(line).append("\n");
                        }

                        userData = builder.toString();
                    }

                    System.out.println("We have the file content!");

                    Task<Void> discardTask = getDriveResourceClient().discardContents(contents);
                    return discardTask;
                }
            })
            .addOnFailureListener(new OnFailureListener()
            {
                @Override
                public void onFailure(@NonNull Exception e)
                {
                    System.out.println("Unable to read file!");
                }
            });
}

I'm pretty sure this can be improved but I guess it's a start for anyone looking for a solution.