使用Paho MqttClient在Android上尝试Mqtt连接 [英] Trying Mqtt connection on Android using Paho MqttClient

问题描述

首次打开该应用程序时，我需要一个屏幕，您可以在其中输入经纪人信息，然后单击尝试并保存".

When you first open the app I want a screen where you can enter the broker information and click try and save.

单击尝试"时，应仅显示一个Snackbar，说明信息是否构成成功的连接.

When clicking try it should just show a Snackbar saying if the information makes for a successful connection.

这是按下尝试"按钮时调用的代码:

This is the code I call when the try button is pressed:

private void tryConnection(View v){
    if(verifyInputs()){
        Snackbar.make(v, getString(R.string.trying_connection), Snackbar.LENGTH_LONG).show();

        String clientId = MqttClient.generateClientId();
        MqttAndroidClient client =
                new MqttAndroidClient(this.getApplicationContext(), getServerAddress(),
                        clientId);

        try {
            IMqttToken token = client.connect();
            final View vinner = v;
            token.setActionCallback(new IMqttActionListener() {
                @Override
                public void onSuccess(IMqttToken asyncActionToken) {
                    // We are connected
                    Snackbar.make(vinner, "Success", Snackbar.LENGTH_LONG).show();

                }

                @Override
                public void onFailure(IMqttToken asyncActionToken, Throwable exception) {
                    // Something went wrong e.g. connection timeout or firewall problems
                    Snackbar.make(vinner, "Fail", Snackbar.LENGTH_LONG).show();
                }
            });
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }
}

问题在于，onFailure似乎在无法连接到服务器时没有被调用，但是在与服务器的连接丢失时却没有被调用.

The problem is, onFailure doesn't seem to be called when it cannot connect to the server, but when a connection to a server is lost.

我该如何测试连接，以便将其存储并返回到主要活动?

How do I just test the connection, so I can store it and go back to the main activity?

推荐答案

好，所以我看不到您的完整服务，任何其他实现或使用方式/位置，因此我提供了MQTT的示例服务.

Ok, so I can't see your full service, any other implementation or how/where you are using this so I'm providing a sample of my MQTT service.

也许您可以比较它，找到任何问题并修复它.

Maybe you can compare it, find any issue and fix it.

或者您也可以使用我的实现.由你决定.希望对您有所帮助.

Or you can just use my implementation. Up to you. Hope it helps.

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.Handler;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.util.Log;

import org.eclipse.paho.android.service.MqttAndroidClient;
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.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttSecurityException;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

import java.util.ArrayList;

public class MyMqttService extends Service implements MqttCallback, IMqttActionListener {

    private final IBinder binder = new MyBinder();

    private MqttAndroidClient mqttClient;
    private MqttConnectOptions mqttConnectOptions;
    private static final MemoryPersistence persistence = new MemoryPersistence();
    private ArrayList<MqttAndroidClient> lostConnectionClients;

    private String clientId = "";
    private boolean isReady = false;
    private boolean doConnectTask = true;
    private boolean isConnectInvoked = false;

    private Handler handler = new Handler();
    private final int RECONNECT_INTERVAL = 10000; // 10 seconds
    private final int DISCONNECT_INTERVAL = 20000; // 20 seconds
    private final int CONNECTION_TIMEOUT = 60;
    private final int KEEP_ALIVE_INTERVAL = 200;

    private String broker_url = "my_broker";

    public MyMqttService() {}

    public class MyBinder extends Binder {
        public MyMqttService getService() {
            return MyMqttService.this;
        }
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return binder;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        initMqttClient();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        disconnectClients();
        if (isConnectInvoked && mqttClient != null && mqttClient.isConnected()) {
            try {
                // unsubscribe here
                unsubscribe("¯\\_(ツ)_/¯");
                mqttClient.disconnect();
            } catch (MqttException e) {
                Log.e("TAG", e.toString());
            }
        }

        handler.removeCallbacks(connect);
        handler.removeCallbacks(disconnect);
    }

    private void initMqttClient() {
        if(mqttClient != null) {
            mqttClient = null;
        }

        lostConnectionClients = new ArrayList<>();

        mqttConnectOptions = new MqttConnectOptions();
        mqttConnectOptions.setCleanSession(true);
        mqttConnectOptions.setConnectionTimeout(CONNECTION_TIMEOUT);
        mqttConnectOptions.setKeepAliveInterval(KEEP_ALIVE_INTERVAL);

        setNewMqttClient();

        handler.post(connect);
        handler.postDelayed(disconnect, DISCONNECT_INTERVAL);
    }

    private void setNewMqttClient() {
        mqttClient = new MqttAndroidClient(MyMqttService.this, broker_url, clientId, persistence);
        mqttClient.setCallback(this);
    }

    public Runnable connect = new Runnable() {
        public void run() {
            connectClient();
            handler.postDelayed(connect, RECONNECT_INTERVAL);
        }
    };

    public Runnable disconnect = new Runnable() {
        public void run() {
            disconnectClients();
            handler.postDelayed(disconnect, DISCONNECT_INTERVAL);
        }
    };

    private void connectClient() {
        if(doConnectTask) {
            doConnectTask = false;

            try {
                isConnectInvoked = true;
                mqttClient.connect(mqttConnectOptions, null, this);
            } catch (MqttException ex) {
                doConnectTask = true;
                Log.e("TAG", ex.toString());
            }
        }
    }

    private void disconnectClients() {
        if (lostConnectionClients.size() > 0) {
            // Disconnect lost connection clients
            for (MqttAndroidClient client : lostConnectionClients) {
                if (client.isConnected()) {
                    try {
                        client.disconnect();
                    } catch (MqttException e) {
                        Log.e("TAG", e.toString());
                    }
                }
            }

            // Close already disconnected clients
            for (int i = lostConnectionClients.size() - 1; i >= 0; i--) {
                try {
                    if (!lostConnectionClients.get(i).isConnected()) {
                        MqttAndroidClient client = lostConnectionClients.get(i);
                        client.close();
                        lostConnectionClients.remove(i);
                    }
                } catch (IndexOutOfBoundsException e) {
                    Log.e("TAG", e.toString());
                }
            }
        }
    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken token) {
        Log.e("TAG", "deliveryComplete()");
    }

    @Override
    public void messageArrived(String topic, MqttMessage message) throws Exception {
        String payload = new String(message.getPayload());
        // do something
    }

    @Override
    public void connectionLost(Throwable cause) {
        Log.e("TAG", cause.getMessage());
    }

    @Override
    public void onSuccess(IMqttToken iMqttToken) {
        isReady = true;

        // subscribe here
         subscribe("¯\\_(ツ)_/¯");
    }

    @Override
    public void onFailure(IMqttToken iMqttToken, Throwable throwable) {
        setNewMqttClient();
        isReady = false;
        doConnectTask = true;
        isConnectInvoked = false;
    }

    private void subscribe(String topic) {
        try {
            mqttClient.subscribe(topic, 0);
            isReady = true;
        } catch (MqttSecurityException mqttSexEx) {
            isReady = false;
        } catch (MqttException mqttEx) {
            isReady = false;
        }
    }

    private void unsubscribe(String topic) {
        try {
            mqttClient.unsubscribe(topic);
        } catch (MqttSecurityException mqttSecEx) {
            Log.e("TAG", mqttSecEx.getMessage());
        } catch (MqttException mqttEx) {
            Log.e("TAG", mqttEx.getMessage());
        }
    }

    private void publish(String topic, String jsonPayload) {
        if(!isReady) {
            return;
        }

        try {
            MqttMessage msg = new MqttMessage();
            msg.setQos(0);
            msg.setPayload(jsonPayload.getBytes("UTF-8"));
            mqttClient.publish(topic, msg);
        } catch (Exception ex) {
            Log.e("TAG", ex.toString());
        }
    }
}

我的另一个建议是只设置本地广播，这样，当您的活动加载并启动该服务时，如果MQTT服务能够连接，则发送一条广播，提示已连接并显示Snackbar.如果连接失败，则发送不同的广播并显示不同的消息.

My other suggestion would be to just setup local broadcast so when your activity loads and you start the service, if MQTT service is able to connect, you send a broadcast saying connected and you show a Snackbar. If connection failed, you send a different broadcast and show a different message.

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