Cloud Firestore + Jetpack Compose — CRUD & Real-Time Sync

#android #kotlin #firebase #firestore

Cloud Firestore provides real-time database synchronization with Jetpack Compose.

Firestore Repository with CallbackFlow

class TaskRepository(private val firestore: FirebaseFirestore) {
    fun getTasks(): Flow<List<Task>> = callbackFlow {
        val listener = firestore.collection("tasks")
            .addSnapshotListener { snapshot, error ->
                if (error != null) {
                    close(error)
                    return@addSnapshotListener
                }
                val tasks = snapshot?.documents?.map { doc ->
                    doc.toObject(Task::class.java)!!
                } ?: emptyList()
                trySend(tasks)
            }
        awaitClose { listener.remove() }
    }
}

Real-Time Sync with addSnapshotListener

fun addTask(task: Task) {
    firestore.collection("tasks")
        .add(task)
        .addOnSuccessListener { ref -> task.id = ref.id }
        .addOnFailureListener { e -> Log.e("Firestore", e) }
}

fun updateTask(taskId: String, updates: Map<String, Any>) {
    firestore.collection("tasks").document(taskId).update(updates)
}

fun deleteTask(taskId: String) {
    firestore.collection("tasks").document(taskId).delete()
}

ViewModel Integration

class TaskViewModel(private val repo: TaskRepository) : ViewModel() {
    val tasks: StateFlow<List<Task>> = repo.getTasks()
        .stateIn(viewModelScope, SharingStarted.Lazily, emptyList())

    fun addTask(title: String) {
        viewModelScope.launch {
            repo.addTask(Task(title = title))
        }
    }
}

TaskList Screen

@Composable
fun TaskListScreen(viewModel: TaskViewModel) {
    val tasks by viewModel.tasks.collectAsState()

    LazyColumn {
        items(tasks) { task ->
            TaskItem(task) { viewModel.deleteTask(task.id) }
        }
    }
}