Google Drive Integration In Flutter (Upload, Download And List Files)

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^0.1.2
  firebase_auth: ^0.15.2
  google_sign_in: ^4.1.0
  flutter_secure_storage: ^3.3.1+1
  googleapis: ^0.54.0
  googleapis_auth: ^0.2.11
  path_provider: ^1.5.1
  file_picker: ^1.3.8

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

class GoogleHttpClient extends IOClient {
  Map<String, String> _headers;

  GoogleHttpClient(this._headers) : super();

  @override
  Future<http.StreamedResponse> send(http.BaseRequest request) =>
      super.send(request..headers.addAll(_headers));

  @override
  Future<http.Response> head(Object url, {Map<String, String> headers}) =>
      super.head(url, headers: headers..addAll(_headers));
}

Step 7. Following is the programming implementation of Google Plus login, logout, file upload to Google Drive, file download, and listing of uploaded files on Google Drive.

Google Login

Future<void> _loginWithGoogle() async {
  signedIn = await storage.read(key: "signedIn") == "true" ? true : false;
  googleSignIn.onCurrentUserChanged
      .listen((GoogleSignInAccount googleSignInAccount) async {
    if (googleSignInAccount != null) {
      _afterGoogleLogin(googleSignInAccount);
    }
  });
  if (signedIn) {
    try {
      googleSignIn.signInSilently().whenComplete(() => () {});
    } catch (e) {
      storage.write(key: "signedIn", value: "false").then((value) {
        setState(() {
          signedIn = false;
        });
      });
    }
  } else {
    final GoogleSignInAccount googleSignInAccount =
        await googleSignIn.signIn();
    _afterGoogleLogin(googleSignInAccount);
  }
}

Future<void> _afterGoogleLogin(GoogleSignInAccount gSA) async {
  googleSignInAccount = gSA;
  final GoogleSignInAuthentication googleSignInAuthentication =
      await googleSignInAccount.authentication;

  final AuthCredential credential = GoogleAuthProvider.getCredential(
    accessToken: googleSignInAuthentication.accessToken,
    idToken: googleSignInAuthentication.idToken,
  );

  final AuthResult authResult = await _auth.signInWithCredential(credential);
  final FirebaseUser user = authResult.user;

  assert(!user.isAnonymous);
  assert(await user.getIdToken() != null);

  final FirebaseUser currentUser = await _auth.currentUser();
  assert(user.uid == currentUser.uid);

  print('signInWithGoogle succeeded: $user');

  storage.write(key: "signedIn", value: "true").then((value) {
    setState(() {
      signedIn = true;
    });
  });
}

Google Logout

void _logoutFromGoogle() async {
  googleSignIn.signOut().then((value) {
    print("User Sign Out");
    storage.write(key: "signedIn", value: "false").then((value) {
      setState(() {
        signedIn = false;
      });
    });
  });
}

Upload File to Google Drive

_uploadFileToGoogleDrive() async {
  var client = GoogleHttpClient(await googleSignInAccount.authHeaders);
  var drive = ga.DriveApi(client);
  ga.File fileToUpload = ga.File();
  var file = await FilePicker.getFile();
  fileToUpload.parents = ["appDataFolder"];
  fileToUpload.name = path.basename(file.absolute.path);
  var response = await drive.files.create(
    fileToUpload,
    uploadMedia: ga.Media(file.openRead(), file.lengthSync()),
  );
  print(response);
}

List Uploaded Files to Google Drive

Future<void> _listGoogleDriveFiles() async {
  var client = GoogleHttpClient(await googleSignInAccount.authHeaders);
  var drive = ga.DriveApi(client);
  drive.files.list(spaces: 'appDataFolder').then((value) {
    setState(() {
      list = value;
    });
    for (var i = 0; i < list.files.length; i++) {
      print("Id: ${list.files[i].id} File Name:${list.files[i].name}");
    }
  });
}

Download Google Drive File

Future<void> _downloadGoogleDriveFile(String fName, String gdID) async {
  var client = GoogleHttpClient(await googleSignInAccount.authHeaders);
  var drive = ga.DriveApi(client);
  ga.Media file = await drive.files
      .get(gdID, downloadOptions: ga.DownloadOptions.FullMedia);
  print(file.stream);

  final directory = await getExternalStorageDirectory();
  print(directory.path);
  final saveFile = File('${directory.path}/${DateTime.now().millisecondsSinceEpoch}$fName');
  List<int> dataStore = [];
  file.stream.listen((data) {
    print("DataReceived: ${data.length}");
    dataStore.insertAll(dataStore.length, data);
  }, onDone: () {
    print("Task Done");
    saveFile.writeAsBytes(dataStore);
    print("File saved at ${saveFile.path}");
  }, onError: (error) {
    print("Some Error");
  });
}

Step 8. Great -- we are done with Google Drive Integration in Flutter. Please check my full source code for it on Git.

In the above source code google-services.json file is not included, you need to set up your own Firebase project and put it in the Android ->app folder.

Conclusion

We have learned how to integrate Google Drive in Flutter and perform upload, download, and list operations.

• Git Repo