Simple Android application

Sure, let's create a simple Android application that displays a "Hello, World!" message when a button is clicked. We'll use Kotlin and Android Studio for development. Here are the steps:

1. **Open Android Studio**: Launch Android Studio and create a new project.

2. **Set up the Project**: Choose "Empty Activity" as the project template and follow the prompts to configure the project details such as name, package name, and language (Kotlin).

3. **Design the Layout**: Open the `activity_main.xml` layout file located in the `res/layout` directory. Design a simple layout with a Button widget in the center of the screen.

```xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity">

    <Button

        android:id="@+id/button"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Click Me"

        android:layout_centerInParent="true"/>

</RelativeLayout>

```

4. **Implement the Logic**: Open the `MainActivity.kt` file located in the `java/com.example.yourappname` directory. Add the code to handle button click events and display the "Hello, World!" message.

```kotlin

package com.example.yourappname

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle

import android.widget.Button

import android.widget.Toast

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {

        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)

        val button = findViewById<Button>(R.id.button)

        button.setOnClickListener {

            Toast.makeText(this, "Hello, World!", Toast.LENGTH_SHORT).show()

        }

    }

}

```

5. **Run the Application**: Connect an Android device or start an emulator and run the application. Click the button, and you should see a toast message displaying "Hello, World!".

That's it! You've created a simple Android application using the Android development framework. This example demonstrates the basics of designing layouts, handling user input, and displaying messages in an Android app. From here, you can explore more advanced topics and build upon this foundation to create more complex applications.