Tutorial: Demo Project

Learn how to build a simple note-taking app with ObjectBox.

This tutorial will walk you through a simple note-taking app explaining how to do basic operations with ObjectBox. To just integrate ObjectBox into your project, look at the Getting Started page.

You can check out the example code from GitHub. This allows you to run the code and explore it in its entirety. It is a simple app for taking notes where you can add new notes by typing in some text and delete notes by clicking on an existing note.

git clone https://github.com/objectbox/objectbox-examples.git
cd objectbox-examples/android-app

git clone https://github.com/objectbox/objectbox-examples.git
cd objectbox-examples/android-app-kotlin

git clone https://github.com/objectbox/objectbox-dart.git
cd objectbox-dart/objectbox/examples/flutter/objectbox_demo

git clone https://github.com/objectbox/objectbox-python.git
cd objectbox-python

The Note entity and Box class

To store notes there is an entity class called Note (or Task in Python). It defines the structure or model of the data persisted (saved) in the database for a note: its id, the note text and the creation date.

src/Note.java

@Entity
public class Note {
    
    @Id
    long id;
    
    String text;
    String comment;
    Date date;
    
    ...
}

src/Note.kt

@Entity
data class Note(
        @Id var id: Long = 0,
        var text: String? = null,
        var comment: String? = null,
        var date: Date? = null
)

lib/model.dart

@Entity()
class Note {
  int id;
  String text;
  String? comment;
  DateTime date;

  ...
}

example/tasks/main.py

@Entity()
class Task:
    id = Id()
    text = String()
    date_created = Date(py_type=int)
    date_finished = Date(py_type=int)

In general, an ObjectBox entity is an annotated class persisted in the database with its properties. In order to extend the note or to create new entities, you simply modify or create new plain classes and annotate them with @Entity and @Id; in Python opt-in uid argument i.e. @Entity(uid=).

Entity Annotations

Go ahead and build the project, for example by using Build > Make project in Android Studio. This triggers ObjectBox to generate some classes, like MyObjectBox.java, and some other classes used by ObjectBox internally.

Go ahead and build the project, for example by using Build > Make project in Android Studio. This triggers ObjectBox to generate some classes, like MyObjectBox.kt, and some other classes used by ObjectBox internally.

Before running the app, run the ObjectBox code generator to create binding code for the entity classes: flutter pub run build_runner build

Also re-run this after changing the note class.

# Make sure to install objectbox >= 4.0.0
$ pip install --upgrade objectbox
$ ls example
ollama 
tasks
vectorsearch-cities

$ cd tasks
$ python main.py

Welcome to the ObjectBox tasks-list app example. Type help or ? for a list of commands.
>

Inserting notes

To see how new notes are added to the database, take a look at the following code fragments. The Box provides database operations for Note objects. A Box is the main interaction with object data.

NoteActivity.java

@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    notesBox = ObjectBox.get().boxFor(Note.class);
    ...
}

Note: In the example project, ObjectBox is the name of a helper class to set up and keep a reference to BoxStore.

NoteActivity.kt

public override fun onCreate(savedInstanceState: Bundle?) {
    ...
    notesBox = ObjectBox.boxStore.boxFor()
    ...
}

Note: In the example project, ObjectBox is the name of a helper class to set up and keep a reference to BoxStore.

lib/objectbox.dart

class ObjectBox {
  late final Store _store;
  late final Box<Note> _box;
  
  ObjectBox._create(this._store) {
    _noteBox = Box<Note>(_store);
    ...

example/tasks/main.py

class TasklistCmd(Cmd):
    # ...

    def __init__(self):
        # ...
        self._store = Store(directory="tasklist-db")
        self._task_box = self._store.box(Task)

When a user adds a note the method addNote() is called. There, a new Note object is created and put into the database using the Box reference:

NoteActivity.java

private void addNote() {
    ...
    Note note = new Note();
    note.setText(noteText);
    note.setComment(comment);
    note.setDate(new Date());
    notesBox.put(note);
    Log.d(App.TAG, "Inserted new note, ID: " + note.getId());
    ...
}

NoteActivity.kt

private fun addNote() {
    ...
    val note = Note(text = noteText, comment = comment, date = Date())
    notesBox.put(note)
    Log.d(App.TAG, "Inserted new note, ID: " + note.id)
    ...
}

lib/objectbox.dart

Future<void> addNote(String text) => _noteBox.putAsync(Note(text));

example/tasks/main.py

def add_task(self, text: str):
    task = Task(text=text, date_created=now_ms())
    self._task_box.put(task)

Note that the ID property (0 when creating the Note object), is assigned by ObjectBox during a put.

Removing/deleting notes

When the user taps a note, it is deleted. The Box provides remove() to achieve this:

NoteActivity.java

OnItemClickListener noteClickListener = new OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Note note = notesAdapter.getItem(position);
        notesBox.remove(note);
        Log.d(App.TAG, "Deleted note, ID: " + note.getId());
        ...
    }
};

NoteActivity.kt

private val noteClickListener = OnItemClickListener { _, _, position, _ ->
    notesAdapter.getItem(position)?.also {
        notesBox.remove(it)
        Log.d(App.TAG, "Deleted note, ID: " + it.id)
    }
    ...
}

lib/objectbox.dart

Future<void> removeNote(int id) => _noteBox.removeAsync(id);

example/tasks/main.py

def remove_task(self, task_id: int) -> bool:
    is_removed = self._task_box.remove(task_id)
    return is_removed

Querying notes

To query and display notes in a list a Query instance is built once:

NoteActivity.java

@Override
public void onCreate(Bundle savedInstanceState) {
    ...
    // Query all notes, sorted a-z by their text.
    notesQuery = notesBox.query().order(Note_.text).build();
    ...
}

NoteActivity.kt

public override fun onCreate(savedInstanceState: Bundle?) {
    ...
    // Query all notes, sorted a-z by their text.
    notesQuery = notesBox.query {
        order(Note_.text)
    }
    ...
}

lib/objectbox.dart

Stream<List<Note>> getNotes() {
  // Query for all notes, sorted by their date.
  // https://docs.objectbox.io/queries
  final builder = _noteBox.query().order(Note_.date, flags: Order.descending);
  ...

example/tasks/main.py

def __init__(self):
    # ...
    self._query = self._task_box.query().build()

And then executed each time any notes change:

NoteActivity.java

private void updateNotes() {
    List<Note> notes = notesQuery.find();
    notesAdapter.setNotes(notes);
}

NoteActivity.kt

private fun updateNotes() {
    val notes = notesQuery.find()
    notesAdapter.setNotes(notes)
}

lib/objectbox.dart

  ...
  // Build and watch the query,
  // set triggerImmediately to emit the query immediately on listen.
  return builder
      .watch(triggerImmediately: true)
      // Map it to a list of notes to be used by a StreamBuilder.
      .map((query) => query.find());
}

example/tasks/main.py

def find_tasks(self):
    return self._query.find()

You can also use self._task_box.get_all() to get all Task objects without any condition (instead of building a query).

In addition to a result sort order, you can add various conditions to filter the results, like equality or less/greater than, when building a query.

ObjectBox Queries

Updating notes and more

What is not shown in the example, is how to update an existing (== the ID is not 0) note. Do so by just modifying any of its properties and then put it again with the changed object:

note.setText("This note has changed.");
notesBox.put(note);

note.text = "This note has changed."
notesBox.put(note)

note.text = "This note has changed.";
_noteBox.putAsync(note);

task.text = "This task has changed."
self._task_box.put(task)

There are additional methods to put, find, query, count or remove entities. Check out the methods of the Box class in API docs (for Java/Kotlin or Dart) to learn more.

Getting started

Setting up the database

Now that you saw ObjectBox in action, how did we get that database (or store) instance? Typically you should set up a BoxStore or Store once for the whole app. This example uses a helper class as recommended in the Getting Started guide.

Getting started

Remember: ObjectBox is a NoSQL database on its own and thus NOT based on SQL or SQLite. That’s why you do not need to set up “CREATE TABLE” statements during initialization.

Note: it is perfectly fine to never close the database. That’s even recommended for most apps.

The Note entity and Box class

Inserting notes

Removing/deleting notes

Querying notes

Updating notes and more

Setting up the database

More In-Depth Tutorials