* 使应用程序在发生与客户机相关的异步事件时得到通知。 * 实现此接口的类可以在这两种类型的客户机上注册{@link IMqttClient#setCallback(MqttCallback)} * 和 {@link IMqttAsyncClient#setCallback(MqttCallback)} *
** Enables an application to be notified when asynchronous * events related to the client occur. * Classes implementing this interface * can be registered on both types of client: {@link IMqttClient#setCallback(MqttCallback)} * and {@link IMqttAsyncClient#setCallback(MqttCallback)} *
*/ public interface MqttCallback { /** * 当与服务器的连接丢失时，将调用此方法。 * @param 造成联系中断的原因。 * * This method is called when the connection to the server is lost. * @param cause the reason behind the loss of connection. */ public void connectionLost(Throwable cause); /** ** 当消息从服务器到达时，将调用此方法。 * *
* 此方法由MQTT客户机同步调用。在此方法干净地返回之前，不会将确认发送回服务器。
*
* 如果该方法的实现抛出一个Exception（异常），则客户机将被关闭。
* 当客户机下一次重新连接时，服务器将重新发送所有服务质量为 1或2的消息。
* 在运行此方法的实现时到达的任何附加消息都将在内存中生成，然后在网络上备份。
** 如果应用程序需要持久化数据， * 那么它应该确保数据在从这个方法返回之前被持久化， * 就像从这个方法返回之后，消息被认为已经被传递了， * 并且是不可复制的。
** 可以发送一个新消息在这个回调的实现(例如,回应这个消息), * 但不得断开客户端实现, * 因为它不可能发送一个确认消息的处理,并会发生死锁。
* * @param topic 消息上主题的名称已发布到 * @param message 实际的消息。 * @throws Exception 如果发生终端错误，应该关闭客户机。 * * ** * This method is called when a message arrives from the server. * *
* This method is invoked synchronously by the MQTT client. An * acknowledgment is not sent back to the server until this * method returns cleanly.
*
* If an implementation of this method throws an Exception, then the
* client will be shut down. When the client is next re-connected, any QoS
* 1 or 2 messages will be redelivered by the server.
* Any additional messages which arrive while an * implementation of this method is running, will build up in memory, and * will then back up on the network.
** If an application needs to persist data, then it * should ensure the data is persisted prior to returning from this method, as * after returning from this method, the message is considered to have been * delivered, and will not be reproducible.
** It is possible to send a new message within an implementation of this callback * (for example, a response to this message), but the implementation must not * disconnect the client, as it will be impossible to send an acknowledgment for * the message being processed, and a deadlock will occur.
* * @param topic name of the topic on the message was published to * @param message the actual message. * @throws Exception if a terminal error has occurred, and the client should be * shut down. * */ public void messageArrived(String topic, MqttMessage message) throws Exception; /** * 当消息的传递已完成，且所有确认已收到时调用。 * 对于QoS 0消息，一旦消息被提交到网络进行交付， * 就会调用它。对于QoS 1，在接收PUBACK时调用它， * 对于QoS 2，在接收PUBCOMP时调用它。 * 令牌将与消息发布时返回的令牌相同。 * * @param token 与消息关联的传递令牌。 * * Called when delivery for a message has been completed, and all * acknowledgments have been received. For QoS 0 messages it is * called once the message has been handed to the network for * delivery. For QoS 1 it is called when PUBACK is received and * for QoS 2 when PUBCOMP is received. The token will be the same * token as that returned when the message was published. * * @param token the delivery token associated with the message. */ public void deliveryComplete(IMqttDeliveryToken token); }