org.apache.tapestry5.corelib.components.Zone

A Zone is portion of the output page designed for easy dynamic updating via Ajax or other client-side effects. A Zone renders out as a div element (or whatever is specified in the template) and may have content initially, or may only get its content as a result of client side activity. Often, Zones are initially invisible, in which case the visible parameter may be set to false (it defaults to true). When a user clicks an ActionLink whose zone parameter is set, the corresponding client-side Tapestry.ZoneManager object is located. It will update the content of the Zone's div and then invoke either a show method (if the div is not visible) or an update method (if the div is visible). The show and update parameters are the names of functions attached to the Tapestry.ElementEffect object. Likewise, a Form component may also trigger an update of a client-side Zone. The server side event handler can return a Block or a component to render as the new content on the client side. Often, re-rendering the Zone's is useful. Multiple client-side zones may be updated by returning a MultiZoneUpdate . Renders informal parameters, adding CSS class "t-zone" and possibly, "t-invisible". You will often want to specify the id parameter of the Zone, in addition to it's Tapestry component id; this "locks down" the client-side id, so the same value is used even in later partial renders of the page (essential if the Zone is nested inside another Zone). When you specify the client-side id, it is used exactly as provided (meaning that you are responsible for ensuring that there will not be an id conflict even in the face of multiple partial renders of the page). Failure to provide an explicit id results in a new, and non-predictable, id being generated for each partial render, which will often result in client-side failures to locate the element to update when the Zone is triggered. After the client-side content is updated, a client-side event is fired on the zone's element. The constant Tapestry.ZONE_UPDATED_EVENT can be used to listen to the event.

[JavaDoc]

Comp onent Parameters

Name	Type	Flags	Default	Default Prefix	Since	Description
elementName	String	Required, NOT Allow Null		literal		The element name to render for the zone; this defaults to the element actually used in the template, or "div" if no specific element was specified.
id	String	NOT Allow Null		literal		If bound, then the id attribute of the rendered element will be this exact value. If not bound, then a unique id is generated for the element.
show	String	NOT Allow Null		literal		Name of a function on the client-side Tapestry.ElementEffect object that is invoked to make the Zone's div visible before being updated. If not specified, then the basic "show" method is used.
update	String	NOT Allow Null		literal		Name of a function on the client-side Tapestry.ElementEffect object that is invoked after the Zone's content has been updated. If not specified, then the basic "highlight" method is used, which performs a classic "yellow fade" to indicate to the user that and update has taken place.
visible	boolean	NOT Allow Null		prop		If true (the default) then the zone will render normally. If false, then the "t-invisible" CSS class is added, which will make the zone initially invisible.

Informal parameters: supported

Related Components

• AjaxFormLoop
• FormFragment

Examples

ZoneDemo.tml (partial)

<t:zone t:id="counterZone" id="counterZone">

  <p>You have clicked the link <strong>${clickCount}</strong> times.</p>

</t:zone>



<p>

<t:actionlink t:id="clicker" zone="counterZone">increment the count</t:actionlink>

</p>

It's pretty standard to bind the id parameter of a zone; the zone parameter of ActionLink and Form are the client-side element id , not the component id. They are often, but not always, the same. Binding the id parameter ensures that a particular, fixed value is used. Binding the zone parameter of the ActionLink is what triggers the partial-render and update logic.

ZoneDemo.java

public class ZoneDemo

{

  @Property

  @Persist

  private int clickCount;



  @InjectComponent

  private Zone counterZone;



  Object onActionFromClicker()

  {

    clickCount++;



    return counterZone.getBody();

  }

}

The event handler method for the clicker component increments the count, then returns the body of the zone. The body will be re-rendered (reflecting the new count), and sent to the client, which will update the zone in place, and trigger and animation (by default, a simple yellow fade) to draw the user's attention.

Not shown here, but fully valid, is to include JavaScript libraries and generate initialization JavaScript. This fully consistent with ordinary full-page renders.