Create Android App

Quick Start Guide

1. Project Overview

We will create a single-screen app to demonstrate the usage of the SDK:
Using Kotlin Compose to create a simple input (amount and reference) and a button to start a transaction.

• The user enters an amount and a transaction reference into a TextField.
• A Button validates the input and starts a transaction.
• A Text label displays a success or error message.

Tested on Android Studio Panda 1 | 2025.3.1

---

2. Implementation Steps

Step 1: Create the Project

1. Open Android Studio and select New Project.
2. Choose Empty Activity (now provides support for Jetpack Compose) or Empty Compose Activity.
3. Name your app (e.g., "HaloInputApp") and ensure the language is Kotlin.
4. Wait for the Gradle sync to finish (watch the bar at the bottom).

Step 2: Add the UI

Open MainActivity.kt. You will see a Greeting function. Replace it with this concise version of your goal:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContent {
        MaterialTheme {
            Surface {
                SimpleInputApp() // implemented below
            }
        }
    }
}

Step 3. The Code (MainActivity.kt)

In a Jetpack Compose project, your UI is defined in Kotlin functions. Replace your setContent block or create a new Composable function:

import androidx.compose.runtime.*
import androidx.compose.material3.*
import androidx.compose.foundation.layout.*
import androidx.compose.ui.*
import androidx.compose.ui.unit.dp

@Composable
fun SimpleInputApp() {
    // 1. State variables to hold input and messages
    var userInput by remember { mutableStateOf("") }
    var resultMessage by remember { mutableStateOf("") }
    var isError by remember { mutableStateOf(false) }

    Column(
        modifier = Modifier
            .fillMaxSize()
            .padding(16.dp),
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Center
    ) {
        // 2. The Input Field
        TextField(
            value = userInput,
            onValueChange = { userInput = it },
            label = { Text("Enter Secret Code") },
            modifier = Modifier.fillMaxWidth()
        )

        Spacer(modifier = Modifier.height(16.dp))

        // 3. The Submit Button
        Button(
            onClick = {
                if (userInput == "1234") {
                    resultMessage = "Success! Access Granted."
                    isError = false
                } else {
                    resultMessage = "Failed! Incorrect Code."
                    isError = true
                }
            },
            modifier = Modifier.fillMaxWidth()
        ) {
            Text("Submit")
        }

        Spacer(modifier = Modifier.height(24.dp))

        // 4. Message Display
        if (resultMessage.isNotEmpty()) {
            Text(
                text = resultMessage,
                color = if (isError) MaterialTheme.colorScheme.error else MaterialTheme.colorScheme.primary,
                style = MaterialTheme.typography.headlineSmall
            )
        }
    }
}

---

Step 4: Run the App

1. Connect an Android device via USB or start an Emulator.
2. Click the Run button (green play icon) in the top toolbar.

---