Importing Existing Sqlite Database in Flutter

Question

I have this Sqlite database file inside the device's 'Documents' folder named backup.db. Now I have written function that should be able to import that database, but I am getting some weird asynchronous errors, not sure what I am doing wrong here, might need to add something. Here's the code for importing the existing file:

    class DbHelper {
  Future initDb() async {
    final dbPath = await ExtStorage.getExternalStoragePublicDirectory(
        ExtStorage.DIRECTORY_DOCUMENTS);
    final path = join(dbPath, '/backup.db');
    final exist = await databaseExists(path);
    if (exist) {
      print('db imported');
      await openDatabase(path);
    } else {
      print('creating copy of database');
      //try {
        //await Directory(dirname(path)).create(recursive: true);
      //} catch (_) {}
      //ByteData data = await rootBundle.load(join(dbPath, '/backup.db'));
      //List<int> bytes =
         // data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
     // await File(path).writeAsBytes(bytes, flush: true);
    }
    await openDatabase(path);
  }
}

As far as I got, it gets the 'documents' directory, merges the path with backup.db file that already exists in Documents, then it should just import it if it exists. Let me know if there is anything I am doing wrong. I am using the ext_storage library to locate the documents folder and sqlite of course to be able to import the database.

And in another screen I call this function like this:

DbHelper dbHelper = new DbHelper();

onTap: () => dbHelper.initDb(),

Here's the stacktrace:

    [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: Unable to load asset: /backup.db
E/flutter (22458): #0      PlatformAssetBundle.load
package:flutter/…/services/asset_bundle.dart:225
E/flutter (22458): <asynchronous suspension>
E/flutter (22458): #1      DbHelper.initDb
package:CWCFlutter/db/import_database.dart:21
E/flutter (22458): <asynchronous suspension>
E/flutter (22458): #2      _FoodListState.build.<anonymous closure>
package:CWCFlutter/food_list.dart:919
E/flutter (22458): #3      GestureRecognizer.invokeCallback
package:flutter/…/gestures/recognizer.dart:183
E/flutter (22458): #4      TapGestureRecognizer.handleTapUp
package:flutter/…/gestures/tap.dart:598
E/flutter (22458): #5      BaseTapGestureRecognizer._checkUp
package:flutter/…/gestures/tap.dart:287
E/flutter (22458): #6      BaseTapGestureRecognizer.acceptGesture
package:flutter/…/gestures/tap.dart:259
E/flutter (22458): #7      GestureArenaManager.sweep
package:flutter/…/gestures/arena.dart:157
E/flutter (22458): #8      GestureBinding.handleEvent
package:flutter/…/gestures/binding.dart:362
E/flutter (22458): #9      GestureBinding.dispatchEvent
package:flutter/…/gestures/binding.dart:338
E/flutter (22458): #10     RendererBinding.dispatchEvent
package:flutter/…/rendering/binding.dart:267
E/flutter (22458): #11     GestureBinding._handlePointerEvent
package:flutter/…/gestures/binding.dart:295
E/flutter (22458): #12     GestureBinding._flushPointerEventQueue
package:flutter/…/gestures/binding.dart:240
E/flutter (22458): #13     GestureBinding._handlePointerDataPacket
package:flutter/…/gestures/binding.dart:213
E/flutter (22458): #14     _rootRunUnary (dart:async/zone.dart:1206:13)
E/flutter (22458): #15     _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter (22458): #16     _CustomZone.runUnaryGuarded (dart:async/zone.dart:1005:7)
E/flutter (22458): #17     _invoke1 (dart:ui/hooks.dart:265:10)
E/flutter (22458): #18     _dispatchPointerDataPacket (dart:ui/hooks.dart:174:5)

updated code

  class DbHelper {
  Future<void> initDB() async {
    Directory documentsDirectory = await getApplicationDocumentsDirectory();
    String newPath = join(documentsDirectory.path, '/backup.db');
    final exist = await databaseExists(newPath);
    print("This print works.");
    if (!exist) {
      try {
        final dbPath = await ExtStorage.getExternalStoragePublicDirectory(
            ExtStorage.DIRECTORY_DOCUMENTS);
        final path = join(dbPath, '/backup.db');
        File(path).copySync(newPath);
        print("This print doesn't work.");
      } catch (_) {}
    }
  }

  Future<Database> openDB() async {
    Directory documentsDirectory = await getApplicationDocumentsDirectory();
    String path = join(documentsDirectory.path, '/backup.db');

    await initDB();
    Database db = await openDatabase(path);

    return db;
  }
}

Answer 1

ByteData data = await rootBundle.load(join(dbPath, '/backup.db'));

You are trying to load "/backup.db" from the asset bundle adding dbPath to the key.

You need to add the backup.db to the assets folder if you want to load the database this way.

If you know the location of the .db file and it's not in the assets then why do you need to import it? Just open it.

You can copy the database to another location using File(path).copy(String newPath)

Future<void> initDB() async {
    Directory documentsDirectory = await getApplicationDocumentsDirectory();
    String newPath = join(documentsDirectory.path, '/backup.db');
    final exist = await databaseExists(newPath);
    if (!exists) {
        try {
            final dbPath = await ExtStorage.getExternalStoragePublicDirectory(
            ExtStorage.DIRECTORY_DOCUMENTS);
            final path = join(dbPath, '/backup.db');
            File(path).copySync(newPath);
        } catch (_) {}
     }
}

Future<Database> openDB() async {
    Directory documentsDirectory = await getApplicationDocumentsDirectory();
    String path = join(documentsDirectory.path, '/backup.db');
    await initDB();
    Database db = await openDatabase(path);
    return db;
}