/**
 * Created by Xinghai.Zhao on 2021/3/17.
 */

public class MQTTService extends Service {

    public static final String TAG = MQTTService.class.getSimpleName();

    private static MqttAndroidClient client;
    private MqttConnectOptions conOpt;

    private String host = "tcp://你要连接的IP地址";
    private String userName = "xxx";
    private String passWord = "xxx";
    private static String myTopic = "xxx";//要订阅的主题      
    private String clientId = "xxx";

    @Override
    public void onCreate() {
        super.onCreate();
        Log.e(getClass().getName(), "onCreate");
        init();
    }

    public static void publish(String msg){
        String topic = myTopic;
        Integer qos = 0;
        Boolean retained = false;
        try {
            if (client != null){
                client.publish(topic, msg.getBytes(), qos.intValue(), retained.booleanValue());
            }
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }

    private void init() {
        // 服务器地址（协议+地址+端口号）
        String uri = host;
        client = new MqttAndroidClient(this, uri, clientId);

        // 设置MQTT监听并且接受消息
        client.setCallback(mqttCallback);

        conOpt = new MqttConnectOptions();
        // 断线重连
        conOpt.setAutomaticReconnect(true);
        // 清除缓存
        conOpt.setCleanSession(true);
        // 设置超时时间，单位：秒
        conOpt.setConnectionTimeout(10);
        // 心跳包发送间隔，单位：秒
        conOpt.setKeepAliveInterval(20);
        // 用户名
        conOpt.setUserName(userName);
        // 密码
        conOpt.setPassword(passWord.toCharArray());     //将字符串转换为字符串数组

        // last will message
        boolean doConnect = true;
        String message = "";
        Log.e(getClass().getName(), "message是:" + message);
        String topic = myTopic;
        Integer qos = 0;
        Boolean retained = false;
        if ((!message.equals("")) || (!topic.equals(""))) {
            // 最后的遗嘱
            // MQTT本身就是为信号不稳定的网络设计的，所以难免一些客户端会无故的和Broker断开连接。
            //当客户端连接到Broker时，可以指定LWT，Broker会定期检测客户端是否有异常。
            //当客户端异常掉线时，Broker就往连接时指定的topic里推送当时指定的LWT消息。
            try {
                conOpt.setWill(topic, message.getBytes(), qos.intValue(), retained.booleanValue());
            } catch (Exception e) {
                Log.i(TAG, "Exception Occured", e);
                doConnect = false;
                iMqttActionListener.onFailure(null, e);
            }
        }

        if (doConnect) {
            doClientConnection();
        }

    }


    @Override
    public void onDestroy() {
        stopSelf();
        try {
            client.disconnect();
        } catch (MqttException e) {
            e.printStackTrace();
        }
        super.onDestroy();
    }

    /** 连接MQTT服务器 */
    private void doClientConnection() {
        if (!client.isConnected() && isConnectIsNormal()) {
            try {
                client.connect(conOpt, null, iMqttActionListener);
            } catch (MqttException e) {
                e.printStackTrace();
            }
        }

    }

    // MQTT是否连接成功
    private IMqttActionListener iMqttActionListener = new IMqttActionListener() {

        @Override
        public void onSuccess(IMqttToken arg0) {
            Log.i(TAG, "连接成功 ");
            try {
                // 订阅myTopic话题
                client.subscribe(myTopic,1);
            } catch (MqttException e) {
                e.printStackTrace();
            }
        }

        @Override
        public void onFailure(IMqttToken arg0, Throwable arg1) {
            arg1.printStackTrace();
            // 连接失败，重连
        }
    };

    // MQTT监听并且接受消息
    private MqttCallback mqttCallback = new MqttCallback() {

        @Override
        public void messageArrived(String topic, MqttMessage message) throws Exception {

            String str1 = new String(message.getPayload());
            String str2 = topic + ";qos:" + message.getQos() + ";retained:" + message.isRetained();
            Log.i(TAG, "messageArrived:" + str1);
            Log.i(TAG, str2);
            // todo 接收到消息后进行后续处理
        }

        @Override
        public void deliveryComplete(IMqttDeliveryToken arg0) {

        }

        @Override
        public void connectionLost(Throwable arg0) {
            // 失去连接，重连
        }
    };

    /** 判断网络是否连接 */
    private boolean isConnectIsNormal() {
        ConnectivityManager connectivityManager = (ConnectivityManager) this.getApplicationContext()
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = connectivityManager.getActiveNetworkInfo();
        if (info != null && info.isAvailable()) {
            String name = info.getTypeName();
            Log.i(TAG, "MQTT当前网络名称：" + name);
            return true;
        } else {
            Log.i(TAG, "MQTT 没有可用网络");
            return false;
        }
    }


    @Override
    public IBinder onBind(Intent intent) {
        Log.e(getClass().getName(), "onBind");
        return new CustomBinder();
    }

    public class CustomBinder extends Binder {
        public MQTTService getService(){
            return MQTTService.this;
        }
    }

}

遗嘱（掉线遗言）（意愿消息）

因为连接的时候提前告知了服务器断开后的处理信息，所以当服务器发现该客户断开连接的时候，会处理改信息。

某资料： （稍后我会将该资料传到资源中）

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