HarmonyOS abstract抽象类实现问题

代码：

//DownloadDataManager.ets
import { DownLoadDataManagerImpl } from './DownLoadDataManagerImpl'
export abstract class DownloadDataManager {
  static create(): DownloadDataManager {
    return new DownLoadDataManagerImpl()
  }
}

//DownLoadDataManagerImpl.ets
import { DownloadDataManager } from './DownloadDataManager';
export class DownLoadDataManagerImpl extends DownloadDataManager {
}

结果报错(错误信息)：

Error message:DownloadDataManager is not initialized
SourceCode:
export class DownLoadDataManagerImpl extends DownloadDataManager {
  ^
  Stacktrace:
    at func_main_0 (entry/src/main/ets/DownLoadDataManagerImpl.ets:4:46)