Adobe® Flex® 4 Language Reference
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mx.collections 
AsyncListView 
Packagemx.collections
Classpublic class AsyncListView
InheritanceAsyncListView Inheritance OnDemandEventDispatcher Inheritance Object
Implements IList

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

The AsyncListView class is an implementation of the IList interface that handles ItemPendingErrors errors thrown by the getItemAt(), removeItemAt(), and toArray() methods.

The getItemAt() method handles ItemPendingErrors by returning a provisional "pending" item until the underlying request succeeds or fails. The provisional item is produced by calling the function specified by the createPendingItemFunction property. . If the request succeeds, the actual item replaces the provisional one. If it fails, the provisional item is replaced with the item returned by calling the function specified by the createFailedItemFunction property.

This class delegates the IList methods and properties to its list. If a list isn't specified, methods that mutate the collection are no-ops, and methods that query the collection return an empty value, such as null or zero as appropriate.

This class is intended to be used with Spark components based on DataGroup, such as List and ComboBox. The Spark classes do not provide intrinsic support for ItemPendingError handling.

AsyncListView does not support re-insertion of pending or failed items. Once a failed or pending item is removed, its connection to a pending request for data is lost. Using drag and drop to move a pending item in an ASyncListView, or sorting an ASyncListView that contains pending or failed items, is not supported because these operations remove and then re-insert list items.

MXML SyntaxexpandedHide MXML Syntax

The <mx:AsyncListView> tag inherits all the attributes of its superclass, and adds the following attributes:

  <mx:AsyncListView
  Properties
    createFailedItemFunction="null"
    createPendingItemFunction="null"
    list="null"
  />
  


Public Properties
 PropertyDefined By
 Inheritedconstructor : Object
A reference to the class object or constructor function for a given object instance.
Object
  createFailedItemFunction : Function
A callback function used to create a substitute item when a request which had caused an ItemPendingError to be thrown, subsequently fails.
AsyncListView
  createPendingItemFunction : Function
A callback function used to create a provisional item when the initial request causes an ItemPendingError to be thrown.
AsyncListView
  length : int
[read-only] The number of items in this collection.
AsyncListView
  list : IList
The IList object that this collection wraps.
AsyncListView
 Inheritedprototype : Object
[static] A reference to the prototype object of a class or function object.
Object
Public Methods
 MethodDefined By
  
AsyncListView(list:IList = null)
Constructor.
AsyncListView
 Inherited
addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void
OnDemandEventDispatcher
  
Adds the specified item to the end of the list.
AsyncListView
  
addItemAt(item:Object, index:int):void
Adds the item at the specified index.
AsyncListView
 Inherited
OnDemandEventDispatcher
  
getItemAt(index:int, prefetch:int = 0):Object
Returns the value of list.getItemAt(index).
AsyncListView
  
Returns the index of the item if it is in the list such that getItemAt(index) == item.
AsyncListView
 Inherited
OnDemandEventDispatcher
 Inherited
Indicates whether an object has a specified property defined.
Object
 Inherited
Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.
Object
  
itemUpdated(item:Object, property:Object = null, oldValue:Object = null, newValue:Object = null):void
Notifies the view that an item has been updated.
AsyncListView
 Inherited
Indicates whether the specified property exists and is enumerable.
Object
  
Removes all items from the list.
AsyncListView
 Inherited
removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void
OnDemandEventDispatcher
  
Removes the actual or pending item at the specified index and returns it.
AsyncListView
  
setItemAt(item:Object, index:int):Object
Places the item at the specified index.
AsyncListView
 Inherited
Sets the availability of a dynamic property for loop operations.
Object
  
Returns an array with the same elements as this AsyncListView.
AsyncListView
 Inherited
Returns the string representation of this object, formatted according to locale-specific conventions.
Object
  
Returns a string that contains the list's length and the number of pending item requests.
AsyncListView
 Inherited
Returns the primitive value of the specified object.
Object
 Inherited
OnDemandEventDispatcher
Events
 Event Summary Defined By
  Dispatched when the list's length has changed or when a list element is replaced.AsyncListView
Property Detail

createFailedItemFunction

property
createFailedItemFunction:Function

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

A callback function used to create a substitute item when a request which had caused an ItemPendingError to be thrown, subsequently fails. The existing item, typically a pending item created by the callback function specified by the createPendingItemFunction() property, is replaced with the failed item.

The value of this property must be a function with two parameters: the index of the requested item, and the failure "info" object, which is passed along from the IResponder fault() method. In most cases you can ignore the second parameter. Shown below is an example implementation of the callback function:

     function createFailedItem(index:int, info:Object):Object
     {
         return "[" + index + "request failed]";        
     }
       

Setting this property does not affect failed items that were already created. Setting this property to null prevents failed items from being created.

The default value is A function that unconditionally returns null..



Implementation
    public function get createFailedItemFunction():Function
    public function set createFailedItemFunction(value:Function):void

See also

createPendingItemFunction

property 
createPendingItemFunction:Function

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

A callback function used to create a provisional item when the initial request causes an ItemPendingError to be thrown. If the request eventually succeeds, the provisional item is automatically replaced by the actual item. If the request fails, then the item is replaced with one created with the callback function specified by the createFailedItemFunction property.

The value of this property must be a function with two parameters: the index of the requested data provider item, and the ItemPendingError itself. In most cases, the second parameter can be ignored. The following example shows an implementation of the callback function:

     function createPendingItem(index:int, ipe:ItemPendingError):Object
     {
         return "[" + index + "request is pending...]";        
     }
       

Setting this property does not affect provisional pending items that were already created. Setting this property to null prevents provisional pending items from being created.

The default value is A function that unconditionally returns null..



Implementation
    public function get createPendingItemFunction():Function
    public function set createPendingItemFunction(value:Function):void

See also

length

property 
length:int  [read-only]

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

The number of items in this collection. 0 means no items while -1 means the length is unknown.

This property can be used as the source for data binding. When this property is modified, it dispatches the collectionChange event.



Implementation
    public function get length():int

list

property 
list:IList

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

The IList object that this collection wraps. That means the object to which all of the IList methods are delegated.

If this property is null, the IList mutation methods, such as setItemAt(), are no-ops. The IList query methods, such getItemAt(), return null or zero (-1 for getItemIndex()), as appropriate.

The default value is null.

This property can be used as the source for data binding. When this property is modified, it dispatches the listChanged event.



Implementation
    public function get list():IList
    public function set list(value:IList):void
Constructor Detail

AsyncListView

()Constructor
public function AsyncListView(list:IList = null)

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Constructor.

Parameters
list:IList (default = null) — Initial value of the list property, the IList we're delegating to.
Method Detail

addItem

()method
public function addItem(item:Object):void

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Adds the specified item to the end of the list. Equivalent to addItemAt(item, length).

Parameters

item:Object — The item to add.

addItemAt

()method 
public function addItemAt(item:Object, index:int):void

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Adds the item at the specified index. The index of any item greater than the index of the added item is increased by one. If the the specified index is less than zero or greater than the length of the list, a RangeError is thrown.

Parameters

item:Object — The item to place at the index.
 
index:int — The index at which to place the item.

getItemAt

()method 
public function getItemAt(index:int, prefetch:int = 0):Object

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Returns the value of list.getItemAt(index).

This method catches ItemPendingErrors (IPEs) generated as a consequence of calling getItemAt(). If an IPE is thrown, an IResponder is added to the IPE and a provisional "pending" item, created with the createPendingItemFunction is returned. If the underlying request eventually succeeds, the pending item is replaced with the real item. If it fails, the pending item is replaced with a value produced by calling createFailedItemFunction.

Parameters

index:int — The list index from which to retrieve the item.
 
prefetch:int (default = 0) — An int indicating both the direction and number of items to fetch during the request if the item is not local.

Returns
Object — The list item at the specified index.

Throws
RangeError — if index < 0 or index >= length.

See also

getItemIndex

()method 
public function getItemIndex(item:Object):int

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Returns the index of the item if it is in the list such that getItemAt(index) == item.

Note: unlike IViewCursor.findxxx() methods, The getItemIndex() method cannot take a parameter with only a subset of the fields in the item being serched for; this method always searches for an item that exactly matches the input parameter.

Parameters

item:Object — The item to find.

Returns
int — The index of the item, or -1 if the item is not in the list.

itemUpdated

()method 
public function itemUpdated(item:Object, property:Object = null, oldValue:Object = null, newValue:Object = null):void

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Notifies the view that an item has been updated. This is useful if the contents of the view do not implement IEventDispatcher and dispatches a PropertyChangeEvent. If a property is specified the view may be able to optimize its notification mechanism. Otherwise it may choose to simply refresh the whole view.

Parameters

item:Object — The item within the view that was updated.
 
property:Object (default = null) — The name of the property that was updated.
 
oldValue:Object (default = null) — The old value of that property. (If property was null, this can be the old value of the item.)
 
newValue:Object (default = null) — The new value of that property. (If property was null, there's no need to specify this as the item is assumed to be the new value.)

removeAll

()method 
public function removeAll():void

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Removes all items from the list.

If any item is not local and an asynchronous operation must be performed, an ItemPendingError will be thrown.

See the ItemPendingError documentation as well as the collections documentation for more information on using the ItemPendingError.

removeItemAt

()method 
public function removeItemAt(index:int):Object

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Removes the actual or pending item at the specified index and returns it. All items whose index is greater than the specified index have their index reduced by 1.

If there is no actual or pending item at the specified index, for example because a call to getItemAt(index) hasn't caused the data to be paged in, then the underlying list may throw an ItemPendingError. The implementation ignores the ItemPendingError and returns null.

Parameters

index:int — The list index from which to retrieve the item.

Returns
Object — The item that was removed or null.

Throws
RangeError — if index < 0 or index >= length.

setItemAt

()method 
public function setItemAt(item:Object, index:int):Object

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Places the item at the specified index. If an item was already at that index the new item will replace it and it will be returned.

Parameters

item:Object — The new item to be placed at the specified index.
 
index:int — The index at which to place the item.

Returns
Object — The item that was replaced, or null if none.

toArray

()method 
public function toArray():Array

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Returns an array with the same elements as this AsyncListView. The array is initialized by retrieving each item with getItemAt(), so pending items are substituted where actual values aren't available yet. The array will not be updated when the AsyncListView replaces the pending items with actual (or failed) values.

Returns
Array — an array with the same elements as this AsyncListView.

toString

()method 
public function toString():String

Language Version: ActionScript 3.0
Product Version: Flex 4
Runtime Versions: Flash Player 10, AIR 1.5

Returns a string that contains the list's length and the number of pending item requests. It does not trigger pending requests.

Returns
String — A brief description of the list.
Event Detail

collectionChange

Event
Event Object Type: mx.events.CollectionEvent
property CollectionEvent.type = mx.events.CollectionEvent.COLLECTION_CHANGE

Language Version: ActionScript 3.0
Product Version: Flex 3
Runtime Versions: Flash Player 9, AIR 1.1

Dispatched when the list's length has changed or when a list element is replaced.

The CollectionEvent.COLLECTION_CHANGE constant defines the value of the type property of the event object for an event that is dispatched when a collection has changed.

The properties of the event object have the following values. Not all properties are meaningful for all kinds of events. See the detailed property descriptions for more information.

PropertyValue
bubblesfalse
cancelablefalse
currentTargetThe Object that defines the event listener that handles the event. For example, if you use myButton.addEventListener() to register an event listener, myButton is the value of the currentTarget.
itemsAn Array of objects with information about the items affected by the event. The contents of this field depend on the event kind; for details see the items property
kindThe kind of event. The valid values are defined in the CollectionEventKind class as constants.
locationLocation within the target collection of the item(s) specified in the items property.
oldLocationthe previous location in the collection of the item specified in the items property.
targetThe Object that dispatched the event; it is not always the Object listening for the event. Use the currentTarget property to always access the Object listening for the event.
typeCollectionEvent.COLLECTION_CHANGE