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.
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
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
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.
Implementation public function get list():IList public function set list(value:IList):void
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 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.
removeItem
()
method
public function removeItem(item:Object):Boolean
Language Version :
ActionScript 3.0
Product Version :
Apache Flex
Runtime Versions :
Flash Player 9, AIR 1.1
Removes the specified item from this list, should it exist.
Relies on ArrayList implementation
Parameters
item:Object — Object reference to the item that should be removed.
Returns
Boolean — Boolean indicating if the item was removed.
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.
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.
Property
Value
bubbles
false
cancelable
false
currentTarget
The 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.
items
An 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
kind
The kind of event.
The valid values are defined in the CollectionEventKind
class as constants.
location
Location within the target collection
of the item(s) specified in the items property.
oldLocation
the previous location in the collection
of the item specified in the items property.
target
The 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.
OnDemandEventDispatcher 
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