事件源在获得字串命令并把它翻译成对应的MonkeyEvent事件后，会把这些事件排队放入一个由事件源维护的队列，然后其他地方如Monkey类的runMonkeyCycles方法就可以去把队列里面的事件取出来进一步进行处理了。那么这里我们先看下属于MonkeySourceNetwork内部类的命令队列的类图:

图6-6-1 命令队列类图

整个继承关系非常清晰简洁，CommandQueue接口定义了一个enqueueEvent方法来往对队列里面追加事件；实现类CommandQueueImpl实现了该方法并且额外提供了一个getNextEvent方法来从其维护的事件队列queuedEvents中获取事件。

因为这个内部接口和内部类的代码量并不多，所以我们以下列出来一并分析:

481     public static interface CommandQueue {

482         /**

483          * Enqueue an event to be returned later.  This allows a

484          * command to return multiple events.  Commands using the

485          * command queue still have to return a valid event from their

486          * translateCommand method.  The returned command will be

487          * executed before anything put into the queue.

488          *

489          * @param e the event to be enqueued.

490          */

491         public void enqueueEvent(MonkeyEvent e);

492     };

493

494     // Queue of Events to be processed.  This allows commands to push

495     // multiple events into the queue to be processed.

496     private static class CommandQueueImpl implements CommandQueue{

497         private final Queue<MonkeyEvent> queuedEvents = new LinkedList<MonkeyEvent>();

498

499         public void enqueueEvent(MonkeyEvent e) {

500             queuedEvents.offer(e);

501         }

502

503         /**

504          * Get the next queued event to excecute.

505          *

506          * @return the next event, or null if there aren't any more.

507          */

508         public MonkeyEvent getNextQueuedEvent() {

509             return queuedEvents.poll();

510         }

511     };

代码6-6-1 CommandQueue和CommandQueueImpl

• 497行: 实例化了一个由MonkeyEvent组成的事件队列queuedEvents
• 499-501: 调用队列Queue的offer方法往事件队列增加一个事件
• 508-510: 调用队列Queue的poll方法从事件队列中取出一个事件并返回