How to run the main function in KMP?

[prestondavid99]

I'm in Android Studio with my KMP project that targets iOS and Android. When I put the main file into my commonMain folder and I try to run the file, it says "Nothing here". How do I actually run the main sample code for the KMQTT Client that was given to me in this repository?

[davidepianca98]

Hello, you cannot run an arbitrary main function in Android, but you have to follow the Activity Lifecycle. This is one simple example I set up, this is a super basic and useless example but it gives a starting point.

fun runClient() {
    CoroutineScope(Dispatchers.IO).launch {
        val client = MQTTClient(
            MQTTVersion.MQTT5,
            "test.mosquitto.org",
            8081,
            TLSClientSettings(serverCertificate = MOSQUITTO_CA_WS),
            keepAlive = 30,
            webSocket = "/mqtt"
        ) {
            println(it.payload?.toByteArray()?.decodeToString())
        }

        client.subscribe(
            listOf(
                Subscription(
                    "test_sub",
                    SubscriptionOptions(Qos.AT_LEAST_ONCE)
                )
            )
        )
        launch {
            while (true) {
                delay(1000)
                client.publish(
                    false,
                    Qos.AT_MOST_ONCE,
                    "test_publish",
                    "hello1".toByteArray().toUByteArray()
                )
            }
        }
        while (client.isRunning()) {
            client.step()
            delay(100)
        }
    }
}

class MainActivity : ComponentActivity() {
    private fun getTlsFilepath(): String {
        val inputStream = application.resources.openRawResource(R.raw.keystore)
        val file = File.createTempFile("keystore", ".p12", application.cacheDir)
        val outputStream = FileOutputStream(file)
        inputStream.use { input ->
            outputStream.use { output ->
                input.copyTo(output)
            }
        }
        return file.absolutePath
    }

    @ExperimentalUnsignedTypes
    fun runBroker() {
        CoroutineScope(Dispatchers.IO).launch {
            val broker = Broker(
                port = 8883,
                tlsSettings = TLSSettings(
                    keyStoreFilePath = getTlsFilepath(),
                    keyStorePassword = "changeit"
                ),
                authentication = null
            )
            broker.listen()
        }
    }

    @OptIn(ExperimentalUnsignedTypes::class)
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            TestKmqttTheme {
                // A surface container using the 'background' color from the theme
                Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colorScheme.background) {
                    Greeting("Android")
                }
            }
        }

        runClient()// or runBroker()
    }
}

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

@Preview(showBackground = true)
@Composable
fun GreetingPreview() {
    TestKmqttTheme {
        Greeting("Android")
    }
}

[prestondavid99]

Thank you for all your hard work on this repo!