在MQTT订户中执行操作
问题描述:
此mqtt订户代码正常工作。我可以轻松订阅在broker.hivemq.com上发布的相关主题的消息。在MQTT订户中执行操作
public class AccelerometerSubscriber implements MqttCallback,
IMqttActionListener {
public static void main(String[] args) throws MqttException {
int QUALITY_OF_SERVICE = 2;
MqttClient client=new MqttClient("tcp://broker.hivemq.com:1883",
MqttClient.generateClientId());
client.setCallback(new SimpleMqttCallBack());
client.connect();
System.out.println("Subscribing ....");
client.subscribe("MQTT Examples"); }
System.out.println("some action"); //------------right here--------------
public void connectionLost(Throwable throwable) {
System.out.println("Connection to MQTT broker lost!"); }
public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
System.out.println("Message received:\n\t"+ new String(mqttMessage.getPayload()));
}
public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
// not used in this example
}}
现在我只想在收到消息时执行操作。我无法做到这一点。
答
你有一个类(AccelerometerSubscriber)实现接口MqttCallback
,使用它的一个实例,而不是做client.setCallback(new SimpleMqttCallBack());
public class AccelerometerSubscriber implements MqttCallback, IMqttActionListener {
public static void main(String[] args) throws MqttException {
AccelerometerSubscriber as = new AccelerometerSubscriber();
int QUALITY_OF_SERVICE = 2;
MqttClient client = new MqttClient("tcp://broker.hivemq.com:1883", MqttClient.generateClientId());
client.setCallback(as);
client.connect();
System.out.println("Subscribing ....");
client.subscribe("MQTT Examples");
}
@Override
public void connectionLost(Throwable throwable) {
System.out.println("Connection to MQTT broker lost!");
}
@Override
public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
//message is received is here!!!
System.out.println("Message received:\n\t" + new String(mqttMessage.getPayload()));
}
@Override
public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
System.out.println("deliveryComplete");
}
@Override
public void onFailure(IMqttToken arg0, Throwable arg1) {
System.out.println("onFailure");
}
@Override
public void onSuccess(IMqttToken arg0) {
System.out.println("onSuccess");
}
}