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我一直在嘗試將MQTT合併到我的Android應用程序中。我原本是在一個活動中工作，並從此嘗試將其移動到服務中以在後臺運行。我能夠連接併發送來自服務的消息，但我無法接收消息。我的服務實現了MqttCallback並覆蓋了messageReceived（）函數，但它似乎永遠不會被調用。有人可以幫我理解爲什麼回調不會觸發嗎？Android PAHO MQTT messageArrived回調不觸發
package com.example.test;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttClientPersistence;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttToken;
import org.eclipse.paho.client.mqttv3.MqttTopic;
import org.eclipse.paho.client.mqttv3.persist.MqttDefaultFilePersistence;
import android.app.Service;
import android.content.Intent;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
public class MqttService extends Service implements MqttCallback{
final static String MY_ACTION = "MqttService";
String username;
//MQTT Variables
MqttClient mySubClient;
MqttConnectOptions connOpt;
String BROKER_URL;
String PUB_TOPIC;
String SUB_TOPIC;
String PUB_CLIENT_ID;
String SUB_CLIENT_ID;
Boolean MqttConnState;
Boolean IsRunning;
static final String TOPIC_BASE = MyProperties.TOPIC_BASE;
static final String PI_BROKER_URL = MyProperties.PI_BROKER_URL; //no encryption
static final String PI_SSL_BROKER_URL = MyProperties.PI_SSL_BROKER_URL; //ssl enabled
@Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i("log_mqtt_service", "Service onStartCommand entered");
//Get session id from previous activity
Bundle extras = intent.getExtras();
if (extras != null) {
username = extras.getString("SESSION_ID");
}
//set mqtt vars
BROKER_URL = PI_BROKER_URL;
PUB_CLIENT_ID = "My-Pub-" + username;
SUB_CLIENT_ID = "My-Sub-" + username;
SUB_TOPIC = TOPIC_BASE + username;
PUB_TOPIC = TOPIC_BASE + "test";
IsRunning = false;
MqttThread myThread = new MqttThread();
myThread.start();
return super.onStartCommand(intent, flags, startId);
}
public class MqttThread extends Thread{
@Override
public void run() {
if(IsRunning==false)
{
IsRunning = true;
connMqtt();
}
while(IsRunning){
//keep thread running
Log.i("log_mqtt_thread_send", "thread sending mqtt message");
sendMsg(PUB_TOPIC, "0x0001", "Message from " + PUB_CLIENT_ID);
}
Log.i("log_mqtt_thread", "thread stopped");
}
}
@Override
public void onDestroy()
{
super.onDestroy();
try {
mySubClient.disconnect();
} catch (MqttException e) {
Log.e ("log_mqtt_disconnect",e.toString());
}
}
@Override
public void connectionLost(Throwable cause) {
// TODO Auto-generated method stub
}
@Override
public void messageArrived(String topic, MqttMessage message)
throws Exception {
String msgStr;
msgStr = new String(message.getPayload());
Log.i("log_mqtt_Rx", "-------------------------------------------------");
Log.i("log_mqtt_Rx", "| Topic: " + topic.toString());
Log.i("log_mqtt_Rx", "| Message: " + msgStr);
Log.i("log_mqtt_Rx", "-------------------------------------------------");
Intent intent = new Intent();
intent.setAction(MY_ACTION);
intent.putExtra("RX_MESSAGE", msgStr);
sendBroadcast(intent);
}
@Override
public void deliveryComplete(IMqttDeliveryToken token) {
// TODO Auto-generated method stub
}
// ------------------------------------------------------------------------
// Function to make mqtt connection and subscribe
// ------------------------------------------------------------------------
int connMqtt()
{
int result=0;
MqttClientPersistence persistence = new MqttDefaultFilePersistence(getBaseContext().getApplicationInfo().dataDir);
try{
Log.i("log_mqtt","mqtt start");
try{
// setup MQTT Client
connOpt = new MqttConnectOptions();
connOpt.setCleanSession(true);
connOpt.setKeepAliveInterval(30);
Log.i("log_mqtt","connOpt vars setup");
}catch(Exception e){
result = -1;
Log.e ("log_mqtt",e.toString());
}
// Connect to Broker for Subscriber connection
try {
mySubClient = new MqttClient(BROKER_URL, SUB_CLIENT_ID, persistence);
Log.i("log_mqtt_conn","create mqttClient");
mySubClient.connect(connOpt);
Log.i("log_mqtt_conn","MQTT client connected to " + BROKER_URL);
} catch (MqttException e) {
result = -2;
Log.i ("log_mqtt_conn","BROKER: " + BROKER_URL);
Log.i ("log_mqtt_conn","SUB_CLIENT_ID: " + SUB_CLIENT_ID);
Log.e ("log_mqtt_conn",e.toString());
}
try {
int subQoS = 0;
mySubClient.subscribe(SUB_TOPIC, subQoS);
Log.i("log_mqtt_sub","mqtt client subscribed to \"" + SUB_TOPIC + "\"");
} catch (Exception e) {
result = -3;
Log.e ("log_mqtt_sub",e.toString());
}
}catch(Exception e){
result = -4;
Log.e ("log_mqtt",e.toString());
}
return result;
}
// ------------------------------------------------------------------------
// Function to send mqtt message to a topic
// ------------------------------------------------------------------------
public void sendMsg(String sendTopic, String msgid, String msg)
{
String timeStamp = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss").format(Calendar.getInstance().getTime());
String pubMsg = "{\"msgid\":\"" + msgid + "\",\"time\":\"" + timeStamp + "\", \"message\":\"" + msg + "\"}";
int pubQoS = 0;
MqttMessage message = new MqttMessage(pubMsg.getBytes());
message.setQos(pubQoS);
message.setRetained(false);
//Topic for publisher
MqttTopic pubTopic = mySubClient.getTopic(sendTopic);
// Publish the message
Log.i("log_mqtt_send","Publishing to topic \"" + pubTopic + "\" qos " + pubQoS);
Log.i("log_mqtt_msg", pubMsg);
MqttDeliveryToken token = null;
try {
// Publish message to broker then disconnect
token = pubTopic.publish(message);
// Wait until the message has been delivered to the broker
token.waitForCompletion();
Thread.sleep(1000);
} catch (Exception ex) {
Log.e("log_mqtt_error",ex.toString());
}
}
}