对paho.MQTT遇到的问题处理两记

<service android:name="org.eclipse.paho.android.service.MqttService"/>

4. MainActivity.java

serverUri 须为【主机的ip】

package com.example.mqtta;import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import org.eclipse.paho.android.service.MqttAndroidClient;
import org.eclipse.paho.client.mqttv3.DisconnectedBufferOptions;
import org.eclipse.paho.client.mqttv3.IMqttActionListener;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.IMqttMessageListener;
import org.eclipse.paho.client.mqttv3.IMqttToken;
import org.eclipse.paho.client.mqttv3.MqttCallbackExtended;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;public class MainActivity extends AppCompatActivity {MqttAndroidClient mqttAndroidClient;// final String serverUri = "tcp://10.96.131.119:1883";String clientId = "test";final String subscriptionTopic = "test";final String publishTopic = "test";final String publishMessage = "Hello World!";final String name = "test";final String password = "test";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);clientId = clientId + System.currentTimeMillis();mqttAndroidClient = new MqttAndroidClient(getApplicationContext(), serverUri, clientId);mqttAndroidClient.setCallback(new MqttCallbackExtended() {@Overridepublic void connectComplete(boolean reconnect, String serverURI) {publishMessage();
//                if (reconnect) {
//                    addToHistory("Reconnected to : " + serverURI);
//                    // Because Clean Session is true, we need to re-subscribe
//                    subscribeToTopic();
//                } else {
//                    addToHistory("Connected to: " + serverURI);
//                }}@Overridepublic void connectionLost(Throwable cause) {}// 处理订阅消息@Overridepublic void messageArrived(String topic, MqttMessage message) throws Exception {Toast.makeText(MainActivity.this, new String(message.getPayload()), Toast.LENGTH_LONG).show();}@Overridepublic void deliveryComplete(IMqttDeliveryToken token) {}});// 连接设置MqttConnectOptions mqttConnectOptions = new MqttConnectOptions();mqttConnectOptions.setAutomaticReconnect(true);mqttConnectOptions.setCleanSession(false);mqttConnectOptions.setUserName(name);mqttConnectOptions.setPassword(password.toCharArray());try {mqttAndroidClient.connect(mqttConnectOptions, null, new IMqttActionListener() {@Overridepublic void onSuccess(IMqttToken asyncActionToken) {
//                    DisconnectedBufferOptions disconnectedBufferOptions = new DisconnectedBufferOptions();
//                    disconnectedBufferOptions.setBufferEnabled(true);
//                    disconnectedBufferOptions.setBufferSize(100);
//                    disconnectedBufferOptions.setPersistBuffer(false);
//                    disconnectedBufferOptions.setDeleteOldestMessages(false);
//                    mqttAndroidClient.setBufferOpts(disconnectedBufferOptions);Toast.makeText(MainActivity.this, "连接成功", Toast.LENGTH_LONG).show();subscribeToTopic();}@Overridepublic void onFailure(IMqttToken asyncActionToken, Throwable exception) {Toast.makeText(MainActivity.this, "连接失败", Toast.LENGTH_LONG).show();
//                    addToHistory("Failed to connect to: " + serverUri);}});} catch (MqttException ex){ex.printStackTrace();}}// 订阅public void subscribeToTopic(){try {mqttAndroidClient.subscribe(subscriptionTopic, 0, null, new IMqttActionListener() {@Overridepublic void onSuccess(IMqttToken asyncActionToken) {Toast.makeText(MainActivity.this, "订阅成功", Toast.LENGTH_SHORT).show();}@Overridepublic void onFailure(IMqttToken asyncActionToken, Throwable exception) {}});
//
//            // THIS DOES NOT WORK!
//            mqttAndroidClient.subscribe(subscriptionTopic, 0, new IMqttMessageListener() {
//                @Override
//                public void messageArrived(String topic, MqttMessage message) throws Exception {
//                    // message Arrived!
//                    System.out.println("Message: " + topic + " : " + new String(message.getPayload()));
//                }
//            });} catch (MqttException ex){System.err.println("Exception whilst subscribing");ex.printStackTrace();}}// 发布public void publishMessage(){try {MqttMessage message = new MqttMessage();message.setPayload(publishMessage.getBytes());mqttAndroidClient.publish(publishTopic, message);Toast.makeText(MainActivity.this, "Message Published", Toast.LENGTH_SHORT).show();if(!mqttAndroidClient.isConnected()){Toast.makeText(MainActivity.this, "Lost of Connected", Toast.LENGTH_SHORT).show();}} catch (MqttException e) {System.err.println("Error Publishing: " + e.getMessage());e.printStackTrace();}}
}

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