Todo App Backend Template
Android — Schema, API & AI Guide

Key Takeaways

Overview

A Todo app is one of the most common starting points for learning backend development. Under the hood it needs user registration, task CRUD, ownership-based access control, and optionally real-time sync.

The schema below defines two classes — _User (built-in) and Todo — connected by a Pointer. With the Back4app Android SDK, you can interact with this backend from your app — querying, creating, updating, and deleting objects — without writing a custom API layer.

Why Build Your Android Todo Backend with Back4app?

Back4app gives Android apps a typed SDK and offline support so you can focus on UX and performance.

• •Kotlin and coroutines: Use the Parse Android SDK with suspend functions and coroutines; type-safe models and less manual JSON.
• •Offline and sync: Pin Todo objects to the local datastore; query from local when offline and sync when back online.
• •Live Queries: Subscribe to Todo changes for real-time UI updates without polling.

Ideal for Android developers using Kotlin and modern async patterns.

Core Benefits

A production-ready Todo backend so you can ship faster and focus on your app.

Technical Stack

Everything powering this Todo app template at a glance.

ER Diagram

Entity-Relationship diagram for the Android Todo app data model.

erDiagram
    _User {
        String objectId PK
        String username
        String email
        String password
        Date createdAt
        Date updatedAt
    }

    Todo {
        String objectId PK
        String title
        Boolean done
        Date dueDate
        Number priority
        Pointer owner FK
        Date createdAt
        Date updatedAt
    }

    _User ||--o{ Todo : "owns"

Integration Flow

Auth-to-CRUD sequence: how your Android app talks to Back4app — login, then query and create todos.

sequenceDiagram
  participant User
  participant App as Android App
  participant Back4app as Back4app Cloud

  User->>App: Login
  App->>Back4app: ParseUser.logInInBackground(username, password)
  Back4app-->>App: Session token
  App-->>User: Logged in

  User->>App: Load todos
  App->>Back4app: ParseQuery<ParseObject>.findInBackground()
  Back4app-->>App: List of Todo
  App-->>User: Show list

  User->>App: Create todo
  App->>Back4app: todo.saveInBackground()
  Back4app-->>App: Todo (objectId)
  App-->>User: Updated list

Data Dictionary

Complete field reference for every class in the schema.

Security & Permissions

How ownership, ACLs, and class-level permissions protect data in this schema.

Schema (JSON)

Raw JSON schema definition — copy and use in your Back4app app or import via the API.

{
  "classes": [
    {
      "className": "Todo",
      "fields": {
        "objectId": {
          "type": "String",
          "required": false
        },
        "title": {
          "type": "String",
          "required": true
        },
        "done": {
          "type": "Boolean",
          "required": false,
          "defaultValue": false
        },
        "dueDate": {
          "type": "Date",
          "required": false
        },
        "priority": {
          "type": "Number",
          "required": false,
          "defaultValue": 3
        },
        "owner": {
          "type": "Pointer",
          "targetClass": "_User",
          "required": false
        },
        "createdAt": {
          "type": "Date",
          "required": false
        },
        "updatedAt": {
          "type": "Date",
          "required": false
        }
      }
    },
    {
      "className": "_User",
      "fields": {
        "objectId": {
          "type": "String",
          "required": false
        },
        "username": {
          "type": "String",
          "required": true
        },
        "email": {
          "type": "String",
          "required": true
        },
        "password": {
          "type": "String",
          "required": true
        },
        "createdAt": {
          "type": "Date",
          "required": false
        },
        "updatedAt": {
          "type": "Date",
          "required": false
        }
      }
    }
  ]
}

API Playground

Try the REST and GraphQL endpoints for the Todo schema. Responses from the example data above — no Back4app account needed.

Uses the same Todo schema as this template.

Step-by-Step Android Integration

Connect to your Back4app backend from a Android app using the Back4app Android SDK.

1. Step 1: Install Back4app Android SDK

   Add the Back4app SDK for your stack (e.g. npm, pubspec, or package manager).

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   // build.gradle.kts (app)
   dependencies {
       implementation("com.github.parse-community.Parse-SDK-Android:parse:4.1.0")
   }

2. Step 2: Initialize Back4app in your app

   Initialize the Back4app SDK at app startup with your App ID and server URL.

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   // Application class or Activity
   Parse.initialize(
       Parse.Configuration.Builder(context)
           .applicationId("YOUR_APP_ID")
           .clientKey("YOUR_CLIENT_KEY")
           .server("https://parseapi.back4app.com/")
           .build()
   );

3. Step 3: Query all todos

   Use the SDK to fetch all Todo objects, sorted by priority.

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   suspend fun getTodos(): List<ParseObject> = withContext(Dispatchers.IO) {
       val query = ParseQuery.getQuery<ParseObject>("Todo")
       query.orderByAscending("priority")
       query.find()
   }

4. Step 4: Create a todo

   Create a new Todo with title, done, and priority, then save.

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   suspend fun createTodo(title: String, priority: Int = 3) = withContext(Dispatchers.IO) {
       val todo = ParseObject("Todo")
       todo.put("title", title)
       todo.put("done", false)
       todo.put("priority", priority)
       todo.save()
   }

5. Step 5: Update and delete todos

   Update fields and save, or delete the object.

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   // Mark done
   suspend fun markDone(objectId: String) = withContext(Dispatchers.IO) {
       val query = ParseQuery.getQuery<ParseObject>("Todo")
       val todo = query.get(objectId)
       todo.put("done", true)
       todo.save()
   }
   
   // Delete
   suspend fun deleteTodo(objectId: String) = withContext(Dispatchers.IO) {
       val query = ParseQuery.getQuery<ParseObject>("Todo")
       query.get(objectId).delete()
   }

Full Data Model

Copy a complete Todo model for type-safe serialization (e.g. class, interface, or type definition).

// Todo.kt — matches Back4app schema
data class Todo(
    val objectId: String?,
    val title: String,
    val done: Boolean,
    val dueDate: Date?,
    val priority: Int,
    val owner: ParseUser?,
    val createdAt: Date?,
    val updatedAt: Date?
) {
    companion object {
        fun from(obj: ParseObject): Todo = Todo(
            objectId = obj.objectId,
            title = obj.getString("title") ?: "",
            done = obj.getBoolean("done") ?: false,
            dueDate = obj.getDate("dueDate"),
            priority = obj.getInt("priority") ?: 3,
            owner = obj.getParseUser("owner"),
            createdAt = obj.createdAt,
            updatedAt = obj.updatedAt
        )
    }
}

Frequently Asked Questions

Common questions about the Todo app backend template.