With the growing demand for mobile app development and the need for faster and more efficient development processes, cross-platform mobile app development has become an attractive solution for many companies. But, as we all know, native apps have their own unique UX/UI features that are hard to replicate in hybrid apps. That's where Kotlin Multiplatform comes in – a game-changing technology that enables developers to write specific code for each platform while sharing common business logic.

In this series, I'll be documenting my journey of developing a simple weather app using Kotlin Multiplatform. In Part 1, we'll focus on setting up the project and designing the UI.

Project Setup

To get started, open Android Studio and select File | New | New Project. From the list of project templates, choose Kotlin Multiplatform App and click Next. Give your app a name and click Next again. For the iOS framework distribution, select Regular framework and keep the default names for the application and shared folders.

Once you've completed these steps, you'll be able to view the full structure of your multiplatform project by switching the view from Android to Project. Each Kotlin Multiplatform project includes three modules: shared, androidApp, and iosApp.

Shared Module

The shared module is a Kotlin module that contains logic common for both Android and iOS applications – code you can share between platforms. It uses Gradle as the build system to automate your build process. The shared module builds into an Android library and an iOS framework.

Android App

The androidApp module is also a Kotlin module that builds into an Android application. Like the shared module, it uses Gradle as the build system. This module depends on and uses the shared module as a regular Android library.

iOS App

The iosApp module is an Xcode project that builds into an iOS application. It also depends on and uses the shared module as an iOS framework. The shared module can be used as a regular framework or as a CocoaPods dependency, based on what you've chosen in the previous step.

UI Design for Android

For the UI design of our weather app, we'll use Jetpack Compose to create a simple layout with three texts: place, temperature, and description. We'll start by replacing the default text with WeatherView(). We'll also adjust the typography size and colors in MyApplicationTheme.kt.

Here's the code for WeatherView():

`kotlin

@Composable

fun WeatherView() {

Column(modifier = Modifier.background(color = Color.Black).padding(24.dp)) {

Text("Montreal", style = MaterialTheme.typography.body1)

Text("19°", style = MaterialTheme.typography.h2)

Text("Clear sky", style = MaterialTheme.typography.body1)

}

}

`

UI Design for iOS

For the UI design of our weather app on iOS, we'll use SwiftUI to create a similar layout with three texts. We'll start by replacing the default text with a new UI that contains three lines of String.

Here's the code for ContentView:

`swift

struct ContentView: View {

var body: some View {

Color.black

.ignoresSafeArea()

.overlay(

VStack {

Text("Montreal").foregroundColor(Color.white).font(.largeTitle)

Text("19°")

.foregroundColor(Color.white)

.font(.system(size: 96))

Text("Clear sky")

.foregroundColor(Color.white)

.font(.largeTitle)

}

)

}

}

`

Note that the UI for Android is using Jetpack Compose, while the UI for iOS is using SwiftUI. I'll assume readers are familiar with these two frameworks.

To be continued in Part 2...

Stay Tuned for More Swift App Development Tips and Tricks!

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