Why Compose is the modern UI toolkit in Android Kotlin

Introduction

Compose helps you build Android app screens faster and easier with less code. It makes your app look great on any device.

When you want to create a new Android app with a modern look and feel.

When you want to update your app UI quickly without writing a lot of code.

When you want your app to work well on phones, tablets, and foldable devices.

When you want to use a simple way to handle user interactions and animations.

When you want to write UI code that is easy to read and maintain.

Syntax

Android Kotlin

import androidx.compose.material.Text
import androidx.compose.runtime.Composable

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

A @Composable function builds part of the UI and can be reused.

Compose uses Kotlin code directly to describe UI, no XML needed.

Examples

Shows a simple text on the screen.

Android Kotlin

@Composable
fun SimpleText() {
  Text("Welcome to Compose!")
}

Displays a greeting message with a name.

Android Kotlin

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

A button that reacts when clicked.

Android Kotlin

import androidx.compose.material.Button
import androidx.compose.material.Text
import androidx.compose.runtime.Composable

@Composable
fun ButtonExample(onClick: () -> Unit) {
  Button(onClick = onClick) {
    Text("Click me")
  }
}

Sample App

This app shows a simple greeting message using Compose. It uses a Surface with the app's background color and a Text composable to display the message.

Android Kotlin

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable

class MainActivity : ComponentActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContent {
      Greeting("Android")
    }
  }
}

@Composable
fun Greeting(name: String) {
  Surface(color = MaterialTheme.colorScheme.background) {
    Text(text = "Hello, $name! Welcome to Compose.")
  }
}

Important Notes

Compose replaces XML layouts with Kotlin code, making UI easier to write and understand.

It automatically updates the screen when data changes, so you don't have to manage UI state manually.

Compose works well with existing Android code, so you can add it gradually to your app.

Summary

Compose lets you build UI with simple Kotlin functions called composables.

It reduces boilerplate code and improves app performance.

Compose is designed for modern Android devices and future UI needs.