| Package | mx.managers |
| Interface | public interface ILayoutManager extends IEventDispatcher |
| Implementors | LayoutManager |
| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
Each phase is distinct from the others and all UIComponents of one phase are processed prior to moving on to the next phase. During the processing of UIComponents in a phase, requests for UIComponents to get re-processed by some phase may occur. These requests are queued and are only processed during the next run of the phase.
The commit phase begins with a call to
validateProperties(), which walks through a list
(reverse sorted by nesting level) of objects calling each object's
validateProperties()
method.
The objects in the list are processed in reversed nesting order, with the least deeply nested object accessed first. This can also be referred to as top-down or outside-in ordering.
This phase allows components whose contents depend on property
settings to configure themselves prior to the measurement
and the layout phases.
For the sake of performance, sometimes a component's property setter
method does not do all the work to update to the new property value.
Instead, the property setter calls the invalidateProperties()
method, deferring the work until this phase runs.
This prevents unnecessary work if the property is set multiple times.
The measurement phase begins with a call to
validateSize(), which walks through a list
(sorted by nesting level) of objects calling each object's
validateSize()
method to determine if the object has changed in size.
If an object's
invalidateSize()
method was previously called,
then the validateSize() method is called.
If the size or position of the object was changed as a result of the
validateSize() call, then the object's
invalidateDisplayList()
method is called, thus adding
the object to the processing queue for the next run of the layout phase.
Additionally, the object's parent is marked for both measurement
and layout phases, by calling
invalidateSize()
and
invalidateDisplayList()
respectively.
The objects in the list are processed by nesting order, with the most deeply nested object accessed first. This can also be referred to as bottom-up inside-out ordering.
The layout phase begins with a call to the
validateDisplayList() method, which walks through a list
(reverse sorted by nesting level) of objects calling each object's
validateDisplayList()
method to request the object to size
and position all components contained within it (i.e. its children).
If an object's
invalidateDisplayList()
method was previously called,
then validateDisplayList() method for the object is called.
The objects in the list are processed in reversed nesting order, with the least deeply nested object accessed first. This can also be referred to as top-down or outside-in ordering.
In general, components do not override the validateProperties(),
validateSize(), or validateDisplayList() methods.
In the case of UIComponents, most components override the
commitProperties(), measure(), or
updateDisplayList() methods, which are called
by the validateProperties(),
validateSize(), or
validateDisplayList() methods, respectively.
At application startup, a single instance of the LayoutManager is created
and stored in the UIComponent.layoutManager property.
All components are expected to use that instance.
If you do not have access to the UIComponent object,
you can also access the LayoutManager using the static
LayoutManager.getInstance() method.
| Property | Defined By | ||
|---|---|---|---|
| usePhasedInstantiation : Boolean
A flag that indicates whether the LayoutManager allows screen updates
between phases. | ILayoutManager | ||
| Method | Defined By | ||
|---|---|---|---|
 | addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void
Registers an event listener object with an EventDispatcher object so that the listener
receives notification of an event. | IEventDispatcher | |
|
Dispatches an event into the event flow. | IEventDispatcher | |
|
Checks whether the EventDispatcher object has any listeners registered for a specific type
of event. | IEventDispatcher | |
Called when a component changes in some way that its layout and/or visuals
need to be changed. | ILayoutManager | ||
Adds an object to the list of components that want their
validateProperties() method called. | ILayoutManager | ||
Adds an object to the list of components that want their
validateSize() method called. | ILayoutManager | ||
Returns true if there are components that need validating;
false if all components have been validated. | ILayoutManager | ||
|
Removes a listener from the EventDispatcher object. | IEventDispatcher | |
When properties are changed, components generally do not apply those changes immediately. | ILayoutManager | ||
When properties are changed, components generally do not apply those changes immediately. | ILayoutManager | ||
|
Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type. | IEventDispatcher | |
usePhasedInstantiation | property |
usePhasedInstantiation:Boolean| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
A flag that indicates whether the LayoutManager allows screen updates
between phases.
If true, measurement and layout are done in phases, one phase
per screen update.
All components have their validateProperties()
and commitProperties() methods
called until all their properties are validated.
The screen will then be updated.
Then all components will have their validateSize()
and measure()
methods called until all components have been measured, then the screen
will be updated again.
Finally, all components will have their
validateDisplayList() and
updateDisplayList() methods called until all components
have been validated, and the screen will be updated again.
If in the validation of one phase, an earlier phase gets invalidated,
the LayoutManager starts over.
This is more efficient when large numbers of components
are being created an initialized. The framework is responsible for setting
this property.
If false, all three phases are completed before the screen is updated.
Implementation
public function get usePhasedInstantiation():Boolean public function set usePhasedInstantiation(value:Boolean):voidinvalidateDisplayList | () | method |
public function invalidateDisplayList(obj:ILayoutManagerClient):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
Called when a component changes in some way that its layout and/or visuals need to be changed. In that case, it is necessary to run the component's layout algorithm, even if the component's size hasn't changed. For example, when a new child component is added, or a style property changes or the component has been given a new size by its parent.
Parameters
obj:ILayoutManagerClient — The object that changed.
|
invalidateProperties | () | method |
public function invalidateProperties(obj:ILayoutManagerClient):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
Adds an object to the list of components that want their
validateProperties() method called.
A component should call this method when a property changes.
Typically, a property setter method
stores a the new value in a temporary variable and calls
the invalidateProperties() method
so that its validateProperties()
and commitProperties() methods are called
later, when the new value will actually be applied to the component and/or
its children. The advantage of this strategy is that often, more than one
property is changed at a time and the properties may interact with each
other, or repeat some code as they are applied, or need to be applied in
a specific order. This strategy allows the most efficient method of
applying new property values.
Parameters
obj:ILayoutManagerClient — The object whose property changed.
|
invalidateSize | () | method |
public function invalidateSize(obj:ILayoutManagerClient):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
Adds an object to the list of components that want their
validateSize() method called.
Called when an object's size changes.
An object's size can change for two reasons:
- The content of the object changes. For example, the size of a
button changes when its
labelis changed. - A script explicitly changes one of the following properties:
minWidth,minHeight,explicitWidth,explicitHeight,maxWidth, ormaxHeight.
When the first condition occurs, it's necessary to recalculate the measurements for the object. When the second occurs, it's not necessary to recalculate the measurements because the new size of the object is known. However, it's necessary to remeasure and relayout the object's parent.
Parameters
obj:ILayoutManagerClient — The object whose size changed.
|
isInvalid | () | method |
public function isInvalid():Boolean| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
Returns true if there are components that need validating;
false if all components have been validated.
Boolean — Returns true if there are components that need validating;
false if all components have been validated.
|
validateClient | () | method |
public function validateClient(target:ILayoutManagerClient, skipDisplayList:Boolean = false):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
When properties are changed, components generally do not apply those changes immediately. Instead the components usually call one of the LayoutManager's invalidate methods and apply the properties at a later time. The actual property you set can be read back immediately, but if the property affects other properties in the component or its children or parents, those other properties may not be immediately updated.
To guarantee that the values are updated,
you can call the validateClient() method.
It updates all properties in all components whose nest level is greater than or equal
to the target component before returning.
Call this method only when necessary as it is a computationally intensive call.
Parameters
target:ILayoutManagerClient — The component passed in is used to test which components
should be validated. All components contained by this component will have their
validateProperties(), commitProperties(),
validateSize(), measure(),
validateDisplayList(),
and updateDisplayList() methods called.
| |
skipDisplayList:Boolean (default = false)true,
does not call the validateDisplayList()
and updateDisplayList() methods.
|
validateNow | () | method |
public function validateNow():void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 3 |
| Runtime Versions: | Flash Player 9, AIR 1.1 |
When properties are changed, components generally do not apply those changes immediately.
Instead the components usually call one of the LayoutManager's invalidate methods and
apply the properties at a later time. The actual property you set can be read back
immediately, but if the property affects other properties in the component or its
children or parents, those other properties may not be immediately updated. To
guarantee that the values are updated, you can call the validateNow() method.
It updates all properties in all components before returning.
Call this method only when necessary as it is a computationally intensive call.
Thu Dec 4 2014, 05:50 PM -08:00