3-STM32+CH395Q(以太网)基本控制篇(自建物联网平台)-编写android连接MQTT服务器程序 这一节编写android连接MQTT服务器程序提示:为

public class MainActivity extends AppCompatActivity {
    //定时器用于轮训订阅主题
    private Timer timerSubscribeTopic = null;
    private TimerTask TimerTaskSubscribeTopic = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        MyMqttClient.sharedCenter().setConnect();

        //MQTT连接成功回调
        MyMqttClient.sharedCenter().setOnServerConnectedCallback(new MyMqttClient.OnServerConnectedCallback() {
            @Override
            public void callback() {
                startTimerSubscribeTopic();//定时订阅主题
            }
        });

        //订阅主题成功回调
        MyMqttClient.sharedCenter().setOnServerSubscribeCallback(new MyMqttClient.OnServerSubscribeSuccessCallback() {
            @Override
            public void callback(String Topic, int qos) {
                if (Topic.equals("1111")){//订阅1111成功
                    stopTimerSubscribeTopic();//订阅到主题,停止订阅
                }
            }
        });
        startTimerSubscribeTopic();//定时订阅主题
    }

    /**
     * 定时器每隔1S尝试订阅主题
     */
    private void startTimerSubscribeTopic(){
        if (timerSubscribeTopic == null) {
            timerSubscribeTopic = new Timer();
        }
        if (TimerTaskSubscribeTopic == null) {
            TimerTaskSubscribeTopic = new TimerTask() {
                @Override
                public void run() {
                    MyMqttClient.sharedCenter().setSubscribe("1111",0);//订阅主题1111,消息等级0
                }
            };
        }
        if(timerSubscribeTopic != null && TimerTaskSubscribeTopic != null )
            timerSubscribeTopic.schedule(TimerTaskSubscribeTopic, 0, 1000);
    }

    private void stopTimerSubscribeTopic(){
        if (timerSubscribeTopic != null) {
            timerSubscribeTopic.cancel();
            timerSubscribeTopic = null;
        }
        if (TimerTaskSubscribeTopic != null) {
            TimerTaskSubscribeTopic.cancel();
            TimerTaskSubscribeTopic = null;
        }
    }

    //当活动不再可见时调用
    @Override
    protected void onStop()
    {
        super.onStop();
        stopTimerSubscribeTopic();//停止定时器订阅
    }
    /**
     * 当处于停止状态的活动需要再次展现给用户的时候，触发该方法
     */
    @Override
    protected void onRestart() {
        super.onRestart();
        startTimerSubscribeTopic();//定时订阅主题
    }
    @Override
    protected void onPause() {
        super.onPause();
        stopTimerSubscribeTopic();
    }
}

MyMqttClient.sharedCenter().setOnServerReadStringCallback(new MyMqttClient.OnServerReadStringCallback() {
            @Override//Topic:主题  Msg.toString():接收的消息  MsgByte:16进制消息
            public void callback(String Topic, MqttMessage Msg, byte[] MsgByte) {
                Log.e("MqttMsg", "Topic: "+Topic+" Msg"+Msg.toString() );
            }
        });

/*连接上MQTT*/
        MyMqttClient.sharedCenter().setOnServerConnectedCallback(new MyMqttClient.OnServerConnectedCallback() {
            @Override
            public void callback() {

            }
        });
        /*和MQTT服务器断开连接*/
        MyMqttClient.sharedCenter().setOnServerDisConnectedCallback(new MyMqttClient.OnServerDisConnectedCallback() {
            @Override
            public void callback(Throwable e) {

            }
        });