我试图列出在谷歌驱动器文件夹中找到的所有文件，查询似乎工作，但当我试图使用.getFiles()获得文件列表的列表是空的。

private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();
    private static final String CREDENTIALS_FILE_PATH = "/serv_acc.json";
    private static final String SERVICE_ACCOUNT = "xxxxxxxxx.iam.gserviceaccount.com";

    private static final String APPLICATION_NAME = "ZZZ-bco-eXXX_oo";
    private static final List<String> SCOPES = Arrays.asList(DriveScopes.DRIVE);
    private static final String ROOT_FOLDER = "XXXXXXXXXXXXXX";

    private static final String projection = "nextPageToken, files(id, name)";
    
    private static Drive driveService;
 

public static void buildApiService() throws IOException, GeneralSecurityException {
        final NetHttpTransport HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
        InputStream resourceAsStream = GoogleDriveApplication.class.getResourceAsStream(CREDENTIALS_FILE_PATH);
        HttpRequestInitializer requestInitializer = new HttpCredentialsAdapter(
                ServiceAccountCredentials.fromStream(resourceAsStream).createScoped(SCOPES).createDelegated(SERVICE_ACCOUNT));
        driveService = new Drive.Builder(HTTP_TRANSPORT, JSON_FACTORY,                       requestInitializer).setApplicationName(APPLICATION_NAME).build();
    }

public static List<File> getChildren(String id) throws IOException {

        String query = "'" + id + "'" + " in parents";

        FileList directChildren = driveService.files().list()
                .setQ(query).setFields(projection).execute();

        System.out.println(directChildren.isEmpty()); // False
        System.out.println(directChildren.size()); // 3
        System.out.println(directChildren.getFiles().isEmpty()); // True
        ...
    }

public static void main(String[] args) throws GeneralSecurityException, IOException {

        buildApiService();
       ....
    }

该文件夹如下所示：
1个子文件夹，1个zip（1，63 Go），1个Xlsx（200Kb）!
请注意：
。当其他进程使用相同的凭据时，相同的凭据在相同的文件夹中起作用（Python代码）
。相同的Java代码可用于其他文件夹
编辑2：我用Python编写了同样的代码。没有对证书或Google驱动器文件夹（权限，权限等）进行任何更改，它工作正常。

# The needed import for service account credentials:
from oauth2client.service_account import ServiceAccountCredentials
from googleapiclient.http import MediaIoBaseDownload
from apiclient.discovery import build
from getfilelistpy import getfilelist
import io
import flatdict
import os
scope = ['https://www.googleapis.com/auth/drive']
# Parsing JSON credentials for a service account:
credentials = ServiceAccountCredentials.from_json_keyfile_name('C:/serv_acc.json', scope)
service = build('drive', 'v3', credentials=credentials)
topFolderId = 'XXXXXXXXXXXXXX'  
resource = {
    "service_account": credentials,
    "id": topFolderId,
    "fields": "files(id,name)",
}
res = getfilelist.GetFileList(resource)
print(dict(res))

服务帐户是有权访问对外部用户打开的文件夹的用户组的一部分。