java - 使用单一连接实例实现 Eclipse MQTT Android 客户端

Question

我在我的应用程序中使用 Eclipse Paho android mqtt 服务。我能够订阅消息并将其发布到 mqtt 代理。我在应用程序中有几个 Activity ，当任何 Activity 开始时，它使用 mqttAndroidClient.connect(null, new IMqttActionListener() {} 连接到代理并在 mqttAndroidClient.setCallback(new MqttCallback() {} 中获取响应。

我的问题:

1. 这是实现 android mqtt 服务的正确方法吗？
2. 有没有办法在整个应用程序中使用相同的连接和回调实例？

Answer 1

“更好”的方法是创建一个连接/重新连接到 MQTT 代理的服务。

我创建了自己的名为 MqttConnectionManagerService 的服务，它维护和管理与代理的连接。

此解决方案的主要特点:

1. 只要服务还活着，服务就会维护一个实例。
2. 如果服务被终止，Android 会重新启动它(因为START_STICKY)
3. 服务可以在设备启动时启动。
4. 服务在后台运行并始终连接以接收通知。
5. 如果服务处于 Activity 状态，再次调用 startService(..) 将触发其 onStartCommand() 方法(而不是 onCreate() ).在此方法中，我们只需检查此客户端是否连接到代理并在需要时连接/重新连接。

示例代码:

MqttConnectionManagerService

public class MqttConnectionManagerService extends Service {

    private MqttAndroidClient client;
    private MqttConnectOptions options;

    @Override
    public void onCreate() {
        super.onCreate();
        options = createMqttConnectOptions();
        client = createMqttAndroidClient();
    }


    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        this.connect(client, options);
        return START_STICKY;
    }

    private MqttConnectOptions createMqttConnectOptions() {
        //create and return options
    }

    private MqttAndroidClient createMqttAndroidClient() {
        //create and return client
    }

    public void connect(final MqttAndroidClient client, MqttConnectOptions options) {

        try {
            if (!client.isConnected()) {
                IMqttToken token = client.connect(options);
                //on successful connection, publish or subscribe as usual
                token.setActionCallback(new IMqttActionListener() {..});
                client.setCallback(new MqttCallback() {..});
            }
        } catch (MqttException e) {
            //handle e
        }
    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="...">

    <!-- Permissions required to receive BOOT_COMPLETED event -->
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <!-- activities go here -->

        <!-- BroadcastReceiver that starts MqttConnectionManagerService on device boot -->
        <receiver android:name=".MqttServiceStartReceiver">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>

        <!-- Services required for using MQTT -->
        <service android:name="org.eclipse.paho.android.service.MqttService" />
        <service android:name=".MqttConnectionManagerService" />
    </application>

</manifest>

MqttServiceStartReceiver

public class MqttServiceStartReceiver extends BroadcastReceiver {    
    @Override
    public void onReceive(Context context, Intent intent) {
        context.startService(new Intent(context, MqttConnectionManagerService.class));
    }
}

In your Activity's onResume()

startService(new Intent(this, MqttConnectionManagerService.class));