private void createFileInAppFolder() {
    final Task<DriveFolder> appFolderTask = getDriveResourceClient().getAppFolder();
    final Task<DriveContents> createContentsTask = getDriveResourceClient().createContents();
    Tasks.whenAll(appFolderTask, createContentsTask)
            .continueWithTask(new Continuation<Void, Task<DriveFile>>() {
                @Override
                public Task<DriveFile> then(@NonNull Task<Void> task) throws Exception {
                    DriveFolder parent = appFolderTask.getResult();
                    DriveContents contents = createContentsTask.getResult();
                    OutputStream outputStream = contents.getOutputStream();
                    try (Writer writer = new OutputStreamWriter(outputStream)) {
                        writer.write("Hello World!");
                    }

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

                    return getDriveResourceClient().createFile(parent, changeSet, contents);
                }
            })
            .addOnSuccessListener(this,
                    new OnSuccessListener<DriveFile>() {
                        @Override
                        public void onSuccess(DriveFile driveFile) {
                            showMessage(getString(R.string.file_created,
                                    driveFile.getDriveId().encodeToString()));
                            finish();
                        }
                    })
            .addOnFailureListener(this, new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    Log.e(TAG, "Unable to create file", e);
                    showMessage(getString(R.string.file_create_error));
                    finish();
                }
            });
}

private fun syncListToDrive() {
        val appFolderTask = mDriveResourceClient?.appFolder
        val createContentsTask = mDriveResourceClient?.createContents()
        Tasks.whenAll(appFolderTask, createContentsTask)
                .continueWithTask(com.google.android.gms.tasks.Continuation<Void, Task<DriveFile>>() {

                })
    }

@Override
public Task<DriveFile> then(@NonNull Task<Void> task) throws Exception {}