使用https://pub.dartlang.org/packages/flutter_downloader。不要忘记进行平台配置。

基本上，这就是您应该使用软件包的方式。链接中有一个详细的详细示例。

final taskId = await FlutterDownloader.enqueue(
  url: 'your download link',
  savedDir: 'the path of directory where you want to save downloaded files',
  showNotification: true, // show download progress in status bar (for Android)
  openFileFromNotification: true, // click on notification to open downloaded file (for Android)
);