Android Basics with Kotlin

Project Setup

Android Studio, New Project, Empty Activity, language Kotlin, minimum SDK 24+. Run on an emulator or your phone via USB debugging.

Your First Screen (Jetpack Compose)

@Composable
fun Greeting(name: String) {
    Text(text = "Hello, $name!")
}

Compose builds UI from functions: state changes recompose only what changed. No XML layouts needed for new apps.

State in Compose

var count by remember { mutableStateOf(0) }
Button(onClick = { count++ }) { Text("Clicked $count") }

Classic Views (Legacy Codebases)

Older apps use XML layouts with findViewById or View Binding. Read them confidently, write new screens in Compose.

Next Steps After Hello

• Navigation Compose for multi-screen apps.
• ViewModel plus StateFlow for screen state.
• Retrofit plus coroutines for network calls.
• Room for offline-first data.

Key Points

• Compose is the modern default; XML is legacy reading skill.
• State plus recomposition replaces adapters and listeners.
• Coroutines and Flow carry over directly from backend Kotlin.