如何使用PHP和MQTT为移动应用添加实时位置共享功能

<?php
require("phpMQTT.php");

$server = "mqtt.example.com"; // MQTT服务器地址
$port = 1883; // MQTT服务端口
$username = "username"; // MQTT用户名
$password = "password"; // MQTT密码
$topic = "location"; // MQTT主题

$mqtt = new phpMQTT($server, $port, "ClientID".rand()); // 创建MQTT客户端
if ($mqtt->connect(true, NULL, $username, $password)) {
    $payload = json_encode(array(
        "lat" => 37.7749, // 纬度
        "lng" => -122.4194 // 经度
    ));
    $mqtt->publish($topic, $payload, 0); // 发布消息
    $mqtt->close(); // 关闭连接
}
?>

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;

public class MainActivity extends AppCompatActivity {

    private final String serverUri = "tcp://mqtt.example.com:1883";
    private final String clientId = "AndroidClient";
    private final String topic = "location";

    private MqttClient mqttClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        try {
            mqttClient = new MqttClient(serverUri, clientId);
            mqttClient.setCallback(new MqttCallback() {
                @Override
                public void connectionLost(Throwable cause) {
                    // 连接丢失时的处理逻辑
                }

                @Override
                public void messageArrived(String topic, MqttMessage message) throws Exception {
                    String payload = new String(message.getPayload());
                    // 处理接收到的位置信息
                }

                @Override
                public void deliveryComplete(IMqttDeliveryToken token) {
                    // 消息发送完成时的处理逻辑
                }
            });
            mqttClient.connect();
            mqttClient.subscribe(topic);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        try {
            mqttClient.disconnect();
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }
}