MQTT从主线程发送消息

Question

我在MqttHelper类中实现了简单的MQTT订阅服务器，该订阅服务器可以正常工作并接收订阅。但是，当我需要从主程序向服务器发送消息时应该如何处理。我有从publish正常运行的方法IMqttActionListener，但是如何在按钮按下事件时从主程序发送文本？

package com.kkk.mqtt.helpers;

import android.content.Context;
import android.util.Log;

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.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;

import java.io.UnsupportedEncodingException;

public class MqttHelper {
    public MqttAndroidClient mqttAndroidClient;

    final String serverUri = "tcp://tailor.cloudmqtt.com:16424";

    final String clientId = "ExampleAndroidClient";
    public final String subscriptionTopic = "sensor";

    final String username = "xxx";
    final String password = "yyy";



    public MqttHelper(Context context){
        mqttAndroidClient = new MqttAndroidClient(context, serverUri, clientId);

        mqttAndroidClient.setCallback(new MqttCallbackExtended() {
            @Override
            public void connectComplete(boolean b, String s) {
                Log.w("mqtt", s);
            }

            @Override
            public void connectionLost(Throwable throwable) {

            }

            @Override
            public void messageArrived(String topic, MqttMessage mqttMessage) throws Exception {
                Log.w("Mqtt", mqttMessage.toString());
            }

            @Override
            public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {

            }
        });
        connect();
    }

    public void setCallback(MqttCallbackExtended callback) {
        mqttAndroidClient.setCallback(callback);
    }


    public void publish(String topic, String info)
    {


        byte[] encodedInfo = new byte[0];
        try {
            encodedInfo = info.getBytes("UTF-8");
            MqttMessage message = new MqttMessage(encodedInfo);
            mqttAndroidClient.publish(topic, message);
            Log.e ("Mqtt", "publish done");
        } catch (UnsupportedEncodingException | MqttException e) {
            e.printStackTrace();
            Log.e ("Mqtt", e.getMessage());
        }catch (Exception e) {
            Log.e ("Mqtt", "general exception "+e.getMessage());
        }

    }

    private void connect(){
        Log.w("Mqtt", "connect start " );
        MqttConnectOptions mqttConnectOptions = new MqttConnectOptions();
        mqttConnectOptions.setAutomaticReconnect(true);
        mqttConnectOptions.setCleanSession(false);
        mqttConnectOptions.setUserName(username);
        mqttConnectOptions.setPassword(password.toCharArray());

        try {

            mqttAndroidClient.connect(mqttConnectOptions, null, new IMqttActionListener()
            {
                @Override
                public void onSuccess(IMqttToken asyncActionToken) {
                    Log.w("Mqtt", "onSuccess " );
                    DisconnectedBufferOptions disconnectedBufferOptions = new DisconnectedBufferOptions();
                    disconnectedBufferOptions.setBufferEnabled(true);
                    disconnectedBufferOptions.setBufferSize(100);
                    disconnectedBufferOptions.setPersistBuffer(false);
                    disconnectedBufferOptions.setDeleteOldestMessages(false);
                    mqttAndroidClient.setBufferOpts(disconnectedBufferOptions);
                    subscribeToTopic();
                    publish(MqttHelper.this.subscriptionTopic,"information");
                }

                @Override
                public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
                    Log.w("Mqtt", "Failed to connect to: " + serverUri + exception.toString());
                }
            });


        } catch (MqttException ex){
            ex.printStackTrace();
        }
    }


    private void subscribeToTopic() {
        try {
            mqttAndroidClient.subscribe(subscriptionTopic, 0, null, new IMqttActionListener() {
                @Override
                public void onSuccess(IMqttToken asyncActionToken) {
                    Log.w("Mqtt","Subscribed!");
                }

                @Override
                public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
                    Log.w("Mqtt", "Subscribed fail!");
                }
            });

        } catch (MqttException ex) {
            System.err.println("Exception whilst subscribing");
            ex.printStackTrace();
        }
    }
}

启动MQTT订阅者的代码：

private void startMqtt() {
    mqttHelper = new MqttHelper(getApplicationContext());
    mqttHelper.setCallback(new MqttCallbackExtended()
    {
        @Override
        public void connectComplete(boolean b, String s) {
            Log.w("Mqtt", "Connect complete"+ s );
        }

        @Override
        public void connectionLost(Throwable throwable) {
            Log.w("Mqtt", "Connection lost" );
        }

        @Override
        public void messageArrived(String topic, MqttMessage mqttMessage) throws Exception {
            Log.w("Mqtt", mqttMessage.toString());
            dataReceived.setText(mqttMessage.toString());
        }

        @Override
        public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
            Log.w("Mqtt", "Delivery complete" );

        }
    });
    Log.w("Mqtt", "will publish");


}

Answer 1

只需让Activity或Fragment实现MqttCallbackExtended接口：

class MainActivity extends AppCompatActivity implements MqttCallbackExtended { 

    ...

    @Override
    public void connectComplete(boolean b, String s) {
        Log.w("Mqtt", "Connect complete"+ s );
    }

    @Override
    public void connectionLost(Throwable throwable) {
        Log.w("Mqtt", "Connection lost" );
    }

    @Override
    public void messageArrived(String topic, MqttMessage mqttMessage) throws Exception {
        Log.w("Mqtt", mqttMessage.toString());
        dataReceived.setText(mqttMessage.toString());
    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
        Log.w("Mqtt", "Delivery complete" );

    }
}

并像这样开始：

void startMqtt(MqttCallbackExtended listener) {
    mqttHelper = new MqttHelper(getApplicationContext());
    mqttHelper.setCallback(listener);
    Log.w("Mqtt", "will publish");
}

在Application中处理这些是有问题的，因为Application没有视图，因此Activity或Fragment和DialogFragment等是实现回调interface的情况。它不是从UI线程运行，而是按照预期的方式异步回调。