Kotlin Mqtt Client

MqttClient.kt

package br.com.hussan.mqttandroid

import android.content.Context
import android.util.Log
import org.eclipse.paho.android.service.MqttAndroidClient
import org.eclipse.paho.client.mqttv3.IMqttActionListener
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken
import org.eclipse.paho.client.mqttv3.IMqttToken
import org.eclipse.paho.client.mqttv3.MqttCallbackExtended
import org.eclipse.paho.client.mqttv3.MqttClient
import org.eclipse.paho.client.mqttv3.MqttException
import org.eclipse.paho.client.mqttv3.MqttMessage

class MqttClient(private val context: Context) {
    val client by lazy {
        val clientId = MqttClient.generateClientId()
        MqttAndroidClient(context, "tcp://iot.eclipse.org:1883",
                clientId)
    }

    companion object {
        const val TAG = "MqttClient"
    }

    fun connect(topics: Array<String>? = null,
                messageCallBack: ((topic: String, message: MqttMessage) -> Unit)? = null) {
        try {
            client.connect()
            client.setCallback(object : MqttCallbackExtended {
                override fun connectComplete(reconnect: Boolean, serverURI: String) {
                    topics?.forEach {
                        subscribeTopic(it)
                    }
                    Log.d(TAG, "Connected to: $serverURI")
                }

                override fun connectionLost(cause: Throwable) {
                    Log.d(TAG, "The Connection was lost.")
                }

                @Throws(Exception::class)
                override fun messageArrived(topic: String, message: MqttMessage) {
                    Log.d(TAG, "Incoming message from $topic: " + message.toString())
                    messageCallBack?.invoke(topic, message)
                }

                override fun deliveryComplete(token: IMqttDeliveryToken) {

                }
            })


        } catch (e: MqttException) {
            e.printStackTrace()
        }
    }

    fun publishMessage(topic: String, msg: String) {

        try {
            val message = MqttMessage()
            message.payload = msg.toByteArray()
            client.publish(topic, message.payload, 0, true)
            Log.d(TAG, "$msg published to $topic")
        } catch (e: MqttException) {
            Log.d(TAG, "Error Publishing to $topic: " + e.message)
            e.printStackTrace()
        }

    }

    fun subscribeTopic(topic: String, qos: Int = 0) {
        client.subscribe(topic, qos).actionCallback = object : IMqttActionListener {
            override fun onSuccess(asyncActionToken: IMqttToken) {
                Log.d(TAG, "Subscribed to $topic")
            }

            override fun onFailure(asyncActionToken: IMqttToken, exception: Throwable) {
                Log.d(TAG, "Failed to subscribe to $topic")
                exception.printStackTrace()
            }
        }
    }

    fun close() {
        client.apply {
            unregisterResources()
            close()
        }
    }
}

Hi! I have a question for you, if you can help me. How can I instantiate the class MqttClient with a context? I'm not able to understand what is a context and which is the meaning of that parameter.
Thanks you a lot!

Hi, Alepazz. Thanks for yout comment.
You can instantiate the MqttClient like this:
https://github.com/hussanhijazi/coffee-iot/blob/403b5945406a38d537b0fc6f19f8c6d551af5253/app/src/main/java/br/com/hussan/coffeeiot/ui/coffee/CoffeeActivity.kt#L29
https://github.com/hussanhijazi/mqtt-android/blob/9c948d71ac3dac83f4204cfaf8dac8a92ade8c3e/app/src/main/java/br/com/hussan/mqttandroid/SensorActivity.kt#L21

We need the context to intatiate the MqttAndroidClient from org.eclipse.paho library

Thanks

thx for this class; it helped me to get started
FYI, I don't believe as is it will compile since MqttClient.generateClientId()

I had to create it which is not a big a deal. I had to return any client id

Many thx again; very helpful