一个“更好”的方法是创建一个Service
它连接/重新连接到 MQTT 代理。
我创建了自己的服务,名为MqttConnectionManagerService
它维护和管理与代理的连接。
该解决方案的主要特点:
- 只要服务还活着,它就会维护一个实例。
- 如果服务被终止,Android 会重新启动它(因为
START_STICKY
)
- 设备启动时可以启动服务。
- 服务在后台运行,并始终保持连接以接收通知。
- 如果服务还活着,调用
startService(..)
再次会触发其onStartCommand()
方法(而不是onCreate()
)。在此方法中,我们只需检查该客户端是否已连接到代理,并根据需要进行连接/重新连接。
示例代码:
MqttConnectionManager服务
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));
}
}
在您的活动中onResume()
startService(new Intent(this, MqttConnectionManagerService.class));