flutter_sqlite_crud

A small Flutter example that demonstrates CRUD operations using the sqflite package and a simple Dish model.

This project is intended as a learning/demo app. It shows how to open and use an SQLite database with a DbHelper class, a minimal UI to create/read/update/delete records, and a few common layout fixes.

Quick links

• Database helper: lib/database/db_helper.dart
• Model: lib/model/dish.dart
• App entry point / UI: lib/main.dart

Requirements

• Flutter SDK (stable channel)
• Platform-specific tooling for Android/iOS if you want to run on device/emulator

Dependencies

The app uses these packages (see pubspec.yaml):

• sqflite — SQLite plugin for Flutter
• path — for building platform-independent file paths

Install dependencies:

flutter pub get

Run the app

Run on a connected device or emulator:

flutter run

Database: DbHelper (explanation)

lib/database/db_helper.dart exposes a small helper class to manage the SQLite database and provides convenience CRUD methods.

Key points:

• Lazy initialization: the db getter (a Future<Database> get db) opens the database on first access and caches the Database instance in a private _db field so subsequent calls reuse the same connection.
• initDb() builds the database path using getDatabasesPath() and join(...), then calls openDatabase(...) and creates the Dishes table if it doesn't exist.
• CRUD methods call the getter then execute SQL using rawInsert, rawUpdate, rawQuery, rawDelete.

Example: get a usable Database instance (from anywhere in the code):

final dbHelper = DbHelper();
final database = await dbHelper.db; // the getter opens/returns the DB
// now use `database` with sqflite APIs

Note: using the helper's convenience methods is recommended (e.g. createDish, readAllDishes) rather than calling SQL directly from UI code.

Schema used in this project

The project creates a single table named Dishes with the following columns:

• name: TEXT
• description: TEXT
• price: DOUBLE

Tip: if you need an id primary key, change the SQL in onCreate to include id INTEGER PRIMARY KEY AUTOINCREMENT.

UI notes and common fixes

The lib/main.dart file contains a minimal UI used to test the DB operations. A few important points and fixes are documented here so you won't run into layout crashes:

• Do not place Expanded (or other flex children) directly inside a SingleChildScrollView's Column. The scroll view provides unbounded height, which causes flex widgets to fail with an error like RenderFlex children have non-zero flex but incoming height constraints are unbounded.

  • Fix: replace Expanded with fixed-height containers or use Wrap / IntrinsicHeight / sized Containers, or move the scrollable to a smaller subtree.

• To show the newest log entries on top, prepend instead of append. Currently log = newEntry + log; will ensure newest messages appear first.

Example usage of the UI helpers

• Create a dish (from main.dart):

final dbHelper = DbHelper();
final dish = Dish('Pizza', 'Cheesy', 9.5);
await dbHelper.createDish(dish);

• Read a dish by name:

final dish = await dbHelper.readDish('Pizza');
print(dish.description);

• Read all dishes:

final list = await dbHelper.readAllDishes();

Troubleshooting

• If you change the table schema you will need to handle migrations (increase the version argument to openDatabase and provide an onUpgrade callback) or uninstall the app to clear the old DB during development.
• If rawQuery returns an empty list, your lookup returned no rows — methods in DbHelper will throw or return empty lists accordingly.

Contributing

Small fixes and improvements welcome. If you add features (like an id primary key, more fields, or migrations), please update DbHelper and the README schema section.

License & notes

This project is an educational example. Use it as a starting point — production apps should use parameterized queries to avoid SQL injection and add proper error handling and migrations.