dependencies {
    ......
    implementation 'org.eclipse.paho:org.eclipse.paho.client.mqttv3:1.1.0'
    implementation 'org.eclipse.paho:org.eclipse.paho.android.service:1.1.1'
}

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/Theme.MyApplication">
    <activity
        android:name=".MainActivity"
        android:exported="true">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <service android:name="org.eclipse.paho.android.service.MqttService"/>
    <service android:name=".MqttActionService"/>
</application>

public class MyMqttClient {
    private MqttAndroidClient mClient;
    private MqttConnectOptions mOptions;
    private OnMqttConnectListener mOnMqttConnectListener;
    private final String mClientId;
    private MqttCallbackExtended mExtended = new MqttCallbackExtended() {
        @Override
        public void connectComplete(boolean reconnect, String serverURI) {
            if (mOnMqttConnectListener != null){
                mOnMqttConnectListener.onConnectComplete(serverURI);
            }
        }
        @Override
        public void connectionLost(Throwable cause) {
            if (mOnMqttConnectListener != null){
                mOnMqttConnectListener.onConnectFailure(cause);
            }
        }
        @Override
        public void messageArrived(String topic, MqttMessage message) throws Exception {
        }
        @Override
        public void deliveryComplete(IMqttDeliveryToken token) {
        }
    };
    private IMqttActionListener mConnectAction = new IMqttActionListener() {
        @Override
        public void onSuccess(IMqttToken asyncActionToken) {
        }
        @Override
        public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
            if (mOnMqttConnectListener != null){
                mOnMqttConnectListener.onConnectFailure(exception);
            }
            exception.printStackTrace();
        }
    };
    private IMqttMessageListener messageListener = new IMqttMessageListener() {
        @Override
        public void messageArrived(String topic, MqttMessage message) throws Exception {
            if (mOnMqttConnectListener != null){
                mOnMqttConnectListener.onMessageArrived(topic, message);
            }
        }
    };
    public MyMqttClient(Context context){
        this(context, null);
    }
    public MyMqttClient(Context context, String clientId){
        if (!TextUtils.isEmpty(clientId)) {
            this.mClientId = clientId;
        }else {
            this.mClientId = MqttConfig.clientId;
        }
        init(context);
    }
    public void init(Context context){
        mClient = new MqttAndroidClient(context, MqttConfig.mqttUrl, mClientId);
        mClient.setCallback(mExtended);
        mOptions = new MqttConnectOptions();
        mOptions.setConnectionTimeout(4000);
        mOptions.setKeepAliveInterval(30);
        mOptions.setUserName(MqttConfig.username);
        mOptions.setPassword(MqttConfig.password.toCharArray());
    }
    public void setOnMqttConnectListener(OnMqttConnectListener onMqttConnectListener) {
        this.mOnMqttConnectListener = onMqttConnectListener;
    }
    /**
     *  連接
     */
    public void connect(){
        try {
            if (!mClient.isConnected()){
                mClient.connect(mOptions, null, mConnectAction);
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    /**
     *  訂閱
     */
    public void subscribeToTopic(String mTopic){
        this.subscribeToTopic(mTopic, 0);
    }
    public void subscribeToTopic(String mTopic, int qos){
        try {
            mClient.subscribe(mTopic, qos, null,null, messageListener);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    /**
     *  發(fā)送消息
     */
    public void sendMessage(String mTopic, byte[] data){
        try {
            MqttMessage message = new MqttMessage();
            message.setPayload(data);
            mClient.publish(mTopic, message);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    public void onDestroy(){
        try {
            mClient.disconnect();
            mExtended = null;
            mConnectAction = null;
            messageListener = null;
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    /**
     *  提供給外層的回調(diào)，更方便進(jìn)行使用
     */
    public interface OnMqttConnectListener{
        void onConnectComplete(String serverURI);
        void onConnectFailure(Throwable e);
        void onMessageArrived(String topic, MqttMessage message);
    }
}

public interface MqttConfig {
    String mqttUrl = "tcp://r0c36017.cn-shenzhen.emqx.cloud:11005";
    String clientId = "deployment-r0c36017";
    String username = "yeshuaishizhenshuai";
    String password = "123456";
    String oneTopic = "kylin/topic/one";
}

class MqttActionService : Service() {
    private var mqttClient : MyMqttClient ?= null
    override fun onCreate() {
        super.onCreate()
        mqttClient = MyMqttClient(this)
        mqttClient?.setOnMqttConnectListener(object : MyMqttClient.OnMqttConnectListener{
            override fun onConnectComplete(serverURI: String?) {
                mqttClient?.subscribeToTopic(MqttConfig.oneTopic)
            }
            override fun onConnectFailure(e: Throwable?) {
            }
            override fun onMessageArrived(topic: String?, message: MqttMessage?) {
                val h = Handler(Looper.getMainLooper())
                h.post {
                    Toast.makeText(this@MqttActionService.applicationContext, message.toString(), Toast.LENGTH_SHORT).show();
                }
            }
        })
    }
    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        val handler = Handler()
        handler.postDelayed({ mqttClient?.connect() }, 1000)
        return START_STICKY
    }
    override fun onBind(intent: Intent?): IBinder? {
        return null
    }
    override fun onDestroy() {
        super.onDestroy()
        mqttClient?.onDestroy()
    }
}

class MainActivity : AppCompatActivity() {
    private var clinet : MyMqttClient ?= null
    private var isConnect = false
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        init()
        val btn : Button = findViewById(R.id.btn_connect)
        val send : Button = findViewById(R.id.btn_send)
        val open : Button = findViewById(R.id.open)
        open.setOnClickListener {
            val intent = Intent()
            intent.setClass(this, MqttActionService::class.java)
            startService(intent)
        }
        btn.setOnClickListener {
            clinet?.connect()
        }
        send.setOnClickListener {
            clinet?.sendMessage(MqttConfig.oneTopic, "你干嘛啊~哎呦~".toByteArray())
        }
    }
    private fun init(){
        clinet = MyMqttClient(this, "deployment-r0c36018")
        clinet?.setOnMqttConnectListener(object : MyMqttClient.OnMqttConnectListener{
            override fun onConnectComplete(serverURI: String?) {
                isConnect = true
            }
            override fun onConnectFailure(e: Throwable?) {
                e?.printStackTrace()
                isConnect = false
            }
            override fun onMessageArrived(topic: String?, message: MqttMessage?) {
            }
        })
    }
}