org.zkoss.zkmax.ui.event.impl
Class GroupEventQueue<T extends Event>

java.lang.Object
  org.zkoss.zkmax.ui.event.impl.GroupEventQueue<T>

All Implemented Interfaces:

java.io.Serializable, EventQueue<T>

public class GroupEventQueue<T extends Event>
extends java.lang.Object
implements EventQueue<T>, java.io.Serializable

The implementation of the group-scoped event queue. A group is a collection of desktops that belongs to the same top browser window. Refer to EventQueues.DESKTOP.

Since:

5.0.4

Author:

tomyeh

See Also:

Serialized Form

Constructor Summary

GroupEventQueue()

Method Summary

void	close() Closes the event queue.
boolean	isClose() Returns whether it is closed.
boolean	isSubscribed(EventListener<T> listener) Returns if an event listener is subscribed.
void	publish(T event) Publishes an event to the queue.
void	subscribe(EventListener<T> listener) Subscribes a listener to this queue.
void	subscribe(EventListener<T> listener, boolean async) Subscribes a synchronous or asynchronous listener to this event queue.
void	subscribe(EventListener<T> listener, EventListener<T> callback) Subscribes a synchronous or asynchronous listener to this event queue.
boolean	unsubscribe(EventListener<T> listener) Unsubscribes a listener from the queue.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GroupEventQueue

public GroupEventQueue()

Method Detail

publish

public void publish(T event)

Description copied from interface: EventQueue

Publishes an event to the queue.

If the scope of a event queue is desktop or group, this method must be called within an activated execution (i.e., Executions.getCurrent() not null), or in an asynchronous listener (see EventQueue).

On the other hand, if the scope is session or application, it is OK to be called without the current execution.

Specified by:

publish in interface EventQueue<T extends Event>

Parameters:

event - the event to publish.
Notice that all subscribers will receive the event no matter what the event's name and target are.
You could publish an anonymous event by publish(new Event("", null, data)).

subscribe

public void subscribe(EventListener<T> listener)

Description copied from interface: EventQueue

Subscribes a listener to this queue. It is the same as subscribe(listener, false) (EventQueue.subscribe(EventListener,boolean). In other words, it subscribes a synchronous listener.

Note: this method must be called within an activated execution (i.e., Executions.getCurrent() not null), no matter what scope the event queue is.

Note: the listener could access the component associated with the event (Event.getTarget()), only if this is an EventQueues.DESKTOP event queue.

An event listener can be subscribed multiple times, and it will be invoked multiple times if an event is published.

Even if this is a EventQueues.GROUP, EventQueues.SESSION, or EventQueues.APPLICATION event queue, the listener is subscribed for the current desktop only, i.e., it can only access the components belong to the subscribed desktop. If you want to use the same listener to manipulate multiple desktops, you have to subscribe them separately when the corresponding execution is available.

Specified by:

subscribe in interface EventQueue<T extends Event>

See Also:

EventQueue.subscribe(EventListener,EventListener), EventQueue.subscribe(EventListener,boolean)

subscribe

public void subscribe(EventListener<T> listener,
                      EventListener<T> callback)

Description copied from interface: EventQueue

Subscribes a synchronous or asynchronous listener to this event queue. A synchronous listener works the same as a normal event listener, while an asynchronous listener is executed asynchronously in an working thread. Refer here for details.

Here is an example,

<window title="long operation" border="normal">
        <zscript>
        void print(String msg) {
                new Label(msg).setParent(inf);
        }
        </zscript>
        <button label="async long op">
                <attribute name="onClick"><![CDATA[
   if (EventQueues.exists("longop")) {
     print("It is busy. Please wait");
     return; //busy
   }

   EventQueue eq = EventQueues.lookup("longop"); //create a queue
   String result;

   //subscribe async listener to handle long operation
   eq.subscribe(new EventListener() {
     public void onEvent(Event evt) { //asynchronous
       org.zkoss.lang.Threads.sleep(3000); //simulate a long operation
       result = "success"; //store the result
     }
   }, new EventListener() { //callback
     public void onEvent(Event evt) {
       print(result); //show the result to the browser
           EventQueues.remove("longop");
         }
   });

   print("Wait for 3 seconds");
   eq.publish(new Event("whatever")); //kick off the long operation
                ]]></attribute>
        </button>
        <vbox id="inf"/>
</window>

Notice that, though an asynchronous listener cannot access the desktop and has no current execution, it can invoke EventQueue.publish(T) to publish the events. Refer to another example in EventQueue.subscribe(EventListener,boolean).

Specified by:

subscribe in interface EventQueue<T extends Event>

Parameters:

listener - the asynchronous listener to invoke when an event is received

callback - the callback listener, which will be invoked if the asynchronous listen has been invoked. Unlike the asynchronous listener, the callback listener works like a normal listener. You can access the current execution, and update the desktop.
Version Difference: since 5.0.8, the event argument is the same as the one passed to listener. In the prior version, it is always null for the callback listener.

See Also:

EventQueue.subscribe(EventListener), EventQueue.subscribe(EventListener,boolean)

subscribe

public void subscribe(EventListener<T> listener,
                      boolean async)

Description copied from interface: EventQueue

Subscribes a synchronous or asynchronous listener to this event queue. A synchronous listener works the same as a normal event listener, while an asynchronous listener is executed asynchronously in an working thread. Refer here for details.

The use of synchronous listeners is straightforward -- they are just the same a normal event listener. Here is an example of using an asynchronous listener. In this example, we use an asynchronous listener to execute a long operation, a synchronous listener to update the desktop, and they communicate with each other with events.

There is another way to do the same job, callback, refer to EventQueue.subscribe(EventListener,EventListener) for example.

<window title="long operation" border="normal">
  <zscript>
  void print(String msg) {
    new Label(msg).setParent(inf);
  }
  </zscript>
  <button label="async long op">
    <attribute name="onClick"><![CDATA[
   if (EventQueues.exists("longop")) {
     print("It is busy. Please wait");
     return; //busy
   }

   EventQueue eq = EventQueues.lookup("longop"); //create a queue
   String result;

   //subscribe async listener to handle long operation
   eq.subscribe(new EventListener() {
     public void onEvent(Event evt) {
       if ("doLongOp".equals(evt.getName())) {
         org.zkoss.lang.Threads.sleep(3000); //simulate a long operation
         result = "success"; //store the result
         eq.publish(new Event("endLongOp")); //notify it is done
       }
     }
   }, true); //asynchronous

   //subscribe a normal listener to show the result to the browser
   eq.subscribe(new EventListener() {
     public void onEvent(Event evt) {
       if ("endLongOp".equals(evt.getName())) {
             print(result); //show the result to the browser
             EventQueues.remove("longop");
           }
         }
   }); //synchronous

   print("Wait for 3 seconds");
   eq.publish(new Event("doLongOp")); //kick off the long operation
    ]]></attribute>
  </button>
  <vbox id="inf"/>
</window>

The asynchronous event listener requires Server Push (ServerPush).

If you want to show a busy message to cover a portion of the desktop, use Clients.showBusy(org.zkoss.zk.ui.Component,String)

Note: this method must be called within an activated execution, i.e., Executions.getCurrent() not null.

An event listener can be subscribed multiple times, and it will be invoked multiple times if an event is published.

Even if this is an application-level or session-level event queue, the listener is subscribed for the current desktop only. If you want to use the same listener for multiple desktops, you have to subscribe them separately when the corresponding execution is available.

Specified by:

subscribe in interface EventQueue<T extends Event>

Parameters:

listener - the listener

async - whether the listener is asynchronous

See Also:

EventQueue.subscribe(EventListener), EventQueue.subscribe(EventListener, EventListener)

unsubscribe

public boolean unsubscribe(EventListener<T> listener)

Description copied from interface: EventQueue

Unsubscribes a listener from the queue.

Note: this method must be called within an activated execution, i.e., Executions.getCurrent() not null.

Notice that this method only unsubscribes the listener subscribed for this desktop. It doesn't check the listeners for other desktops even if this is an application-level or session-level event queue.

Specified by:

unsubscribe in interface EventQueue<T extends Event>

Returns:

true if the listener was subscribed.

isSubscribed

public boolean isSubscribed(EventListener<T> listener)

Description copied from interface: EventQueue

Returns if an event listener is subscribed.

Notice that this method only checks the listeners subscribed for this desktop. It doesn't check the listeners for other desktops even if this is an application-level or session-level event queue.

Specified by:

isSubscribed in interface EventQueue<T extends Event>

close

public void close()

Description copied from interface: EventQueue

Closes the event queue. After closed, application cannot access any of its method.

Don't call this method directly. It is called only internally. Rather, use EventQueues.remove(java.lang.String) instead.

Specified by:

close in interface EventQueue<T extends Event>

isClose

public boolean isClose()

Description copied from interface: EventQueue

Returns whether it is closed.

Specified by:

isClose in interface EventQueue<T extends Event>