Kotlin

Mobile development is hard. Cross-platform mobile development is harder. Kotlin Multiplatform sits in the middle — shared business logic with native UI on each platform. The Gradle configuration alone can take hours. Can Claude handle it? This is the most technically challenging project in the entire series. KMP has expect/actual declarations, platform-specific dependency injection, multiplatform Gradle config, and two completely different UI frameworks (Jetpack Compose for Android, SwiftUI for iOS). ...

This is the hardest project in Part 2. Kotlin Multiplatform has a complex build system, platform-specific code patterns, and a Gradle configuration that can break in surprising ways. Can Claude handle it? I was skeptical going in. KMP projects have dozens of Gradle files, expect/actual declarations, and platform-specific dependencies that need to match exact versions. One wrong version number and nothing compiles. Total time: 4 hours 31 minutes. 6 prompts. Most of the time was fighting Gradle. ...

Mobile development is where AI tools face their toughest test. Android has complex APIs, Jetpack Compose changes fast, and platform-specific patterns do not always match what AI learned from web development tutorials. In this article, you will build a complete notes app with Kotlin and Jetpack Compose. You will use Claude Code as the primary tool (running alongside Android Studio) and Copilot for inline completions. Every prompt, every AI mistake, and every manual fix is shown. ...

Android 16 ships a platform feature called App Functions. It lets an AI assistant — like Google Gemini — discover and call typed functions inside your app from a natural-language request, without the user opening your app. You annotate a suspend fun with @AppFunction. A KSP compiler plugin reads your KDoc and turns it into an XML schema. Android indexes that schema when the app installs. When a user says “set a 10-minute pasta timer,” an assistant like Gemini matches the request to your function and calls it. Your function runs locally, inside your app’s own process. ...

You have built a complete Ktor backend with authentication, database, WebSockets, Docker, and CI/CD. Now it is time to connect everything — a Kotlin backend and a Kotlin client sharing the same data models. In this final tutorial, you will create shared data models, build a Ktor Client that consumes your API, and see how a KMP mobile app connects to your backend. The Full-Stack Kotlin Vision Most full-stack projects look like this: ...

Your API has many endpoints. Other developers need to know how to use them. They need to know the request format, response format, required headers, and possible error codes. Writing documentation by hand is tedious and quickly becomes outdated. In this tutorial, you will add OpenAPI documentation and Swagger UI to your Ktor API. Developers can browse your API at /docs and try out endpoints directly from the browser. What is OpenAPI? OpenAPI (formerly Swagger) is a standard format for describing REST APIs. It is a YAML or JSON file that lists all endpoints, request bodies, response schemas, authentication, and more. ...

Your API has registration and login with email and password. But many users prefer to sign in with their Google account. It is faster and they do not need to remember another password. In this tutorial, you will add Google Sign-In using OAuth 2.0. You will learn how the OAuth flow works, how to handle the callback, and how to link OAuth accounts with existing email accounts. How OAuth 2.0 Works OAuth 2.0 is a protocol that lets users sign in with a third-party provider (Google, GitHub, etc.) without sharing their password with your application. ...

You decided to build a backend with Kotlin. Good choice. But now you face another decision: Ktor or Spring Boot? Both are great frameworks. Both support Kotlin. But they are very different in philosophy, design, and use cases. Let’s compare them honestly. The Big Picture Ktor is a lightweight, modular framework built by JetBrains. It is Kotlin-native, coroutine-based, and you add features as plugins. Spring Boot is a full-featured, batteries-included framework from VMware (now Broadcom). It started as a Java framework and added Kotlin support later. ...

Android development has changed a lot in the past few years. The ecosystem is no longer centered on XML layouts and basic CRUD apps. In 2026, Android development is shaped by AI-native features, Kotlin-first tooling, multiplatform code, and performance engineering. Many developers are still learning patterns that teams are already moving away from. So the real question is no longer: “How do I build Android apps?” The real question is: ...

You have an existing Android app. It works. Users like it. Now the team wants an iOS version. Rewriting from scratch in Swift takes months. Kotlin Multiplatform lets you share the business logic and add iOS on top, without rewriting everything. In this final tutorial, we cover how to migrate an existing Android app to KMP. This is not a “rewrite from scratch” approach. It is a gradual migration — move one layer at a time, keep the Android app working at every step, and add iOS when the shared module is ready. ...