Package org.zkoss.zkmax.ui.event.impl

Class GroupEventQueue<T extends Event>

  • 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 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,
                      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>