| Package | spark.layouts.supportClasses |
| Class | public class LayoutBase |
| Inheritance | LayoutBase  OnDemandEventDispatcher Object |
| Subclasses | BasicLayout, ButtonBarHorizontalLayout, ConstraintLayout, HorizontalLayout, TabbedViewNavigatorTabBarHorizontalLayout, TileLayout, VerticalLayout, ViewMenuLayout |
| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
LayoutBase or one of its subclasses.
At minimum, subclasses must implement the updateDisplayList()
method, which positions and sizes the target GroupBase's elements, and
the measure() method, which calculates the default
size of the target.
Subclasses may override methods like getElementBoundsAboveScrollRect()
and getElementBoundsBelowScrollRect() to customize the way
the target behaves when it's connected to scrollbars.
Subclasses that support virtualization must respect the
useVirtualLayout property and should only retrieve
layout elements within the scrollRect (the value of
getScrollRect()) using getVirtualElementAt()
from within updateDisplayList().
Show MXML Syntax
Hide MXML SyntaxThe <s:LayoutBase> tag inherits all of the tag
attributes of its superclass and adds the following tag attributes:
<s:LayoutBase
Properties
clipAndEnableScrolling="false"
dropIndicator="defined by the skin class"
horizontalScrollPosition="0"
target="null"
typicalLayoutElement="null"
useVirtualLayout="false"
verticalScrollPosition="0"
/>
| Property | Defined By | ||
|---|---|---|---|
| clipAndEnableScrolling : Boolean
If true, specifies to clip the children to the boundaries of the viewport. | LayoutBase | ||
 | constructor : Object
A reference to the class object or constructor function for a given object instance. | Object | |
| dropIndicator : DisplayObject
The DisplayObject that this layout uses for
the drop indicator during a drag-and-drop operation. | LayoutBase | ||
| horizontalScrollPosition : Number
The x coordinate of the origin of the viewport in the component's coordinate system,
where the default value is (0,0) corresponding to the upper-left corner of the component. | LayoutBase | ||
| target : GroupBase
The GroupBase container whose elements are measured, sized and positioned
by this layout. | LayoutBase | ||
| typicalLayoutElement : ILayoutElement
Used by layouts when fixed row/column sizes are requested but
a specific size isn't specified. | LayoutBase | ||
| useVirtualLayout : Boolean
A container can hold any number of children. | LayoutBase | ||
| verticalScrollPosition : Number
The y coordinate of the origin of the viewport in the component's coordinate system,
where the default value is (0,0) corresponding to the upper-left corner of the component. | LayoutBase | ||
| Method | Defined By | ||
|---|---|---|---|
Constructor. | LayoutBase | ||
| 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. | OnDemandEventDispatcher | |
Calculates the drop location in the data provider of the drop target for
the specified dragEvent. | LayoutBase | ||
When useVirtualLayout is true,
this method can be used by the layout target
to clear cached layout information when the target changes. | LayoutBase | ||
|
Dispatches an event into the event flow. | OnDemandEventDispatcher | |
Called by the target after a layout element
has been added and before the target's size and display list are
validated. | LayoutBase | ||
This method must is called by the target after a layout element
has been removed and before the target's size and display list are
validated. | LayoutBase | ||
Returns the specified element's layout bounds as a Rectangle or null
if the index is invalid, the corresponding element is null,
includeInLayout=false,
or if this layout's target property is null. | LayoutBase | ||
Returns the change to the horizontal scroll position to handle
different scrolling options. | LayoutBase | ||
getNavigationDestinationIndex(currentIndex:int, navigationUnit:uint, arrowKeysWrapFocus:Boolean):int
Delegation method that determines which item
to navigate to based on the current item in focus
and user input in terms of NavigationUnit. | LayoutBase | ||
Computes the verticalScrollPosition and
horizontalScrollPosition deltas needed to
scroll the element at the specified index into view. | LayoutBase | ||
Returns the change to the vertical scroll position to handle
different scrolling options. | LayoutBase | ||
|
Checks whether the EventDispatcher object has any listeners registered for a specific type
of event. | OnDemandEventDispatcher | |
|
Indicates whether an object has a specified property defined. | Object | |
Hides the previously shown drop indicator,
created by the showDropIndicator() method,
removes it from the display list and also stops the drag scrolling. | LayoutBase | ||
|
Indicates whether an instance of the Object class is in the prototype chain of the object specified
as the parameter. | Object | |
Measures the target's default size based on its content, and optionally
measures the target's default minimum size. | LayoutBase | ||
|
Indicates whether the specified property exists and is enumerable. | Object | |
|
Removes a listener from the EventDispatcher object. | OnDemandEventDispatcher | |
|
Sets the availability of a dynamic property for loop operations. | Object | |
Sizes, positions and parents the drop indicator based on the specified
drop location. | LayoutBase | ||
|
Returns the string representation of this object, formatted according to locale-specific conventions. | Object | |
|
Returns the string representation of the specified object. | Object | |
Sizes and positions the target's elements. | LayoutBase | ||
Called by the target at the end of its updateDisplayList
to have the layout update its scrollRect. | LayoutBase | ||
|
Returns the primitive value of the specified object. | Object | |
|
Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type. | OnDemandEventDispatcher | |
| Method | Defined By | ||
|---|---|---|---|
Calculates how much to scroll for the specified dropLocation
during a drag and drop gesture. | LayoutBase | ||
Returns the index where a new item should be inserted if
the user releases the mouse at the specified coordinates
while completing a drag and drop gesture. | LayoutBase | ||
Calculates the bounds for the drop indicator that provides visual feedback
to the user of where the items will be inserted at the end of a drag and drop
gesture. | LayoutBase | ||
Returns the bounds of the first layout element that either spans or
is above the scrollRect's top edge. | LayoutBase | ||
Returns the bounds of the first layout element that either spans or
is below the scrollRect's bottom edge. | LayoutBase | ||
Returns the bounds of the first layout element that either spans or
is to the left of the scrollRect's left edge. | LayoutBase | ||
Returns the bounds of the first layout element that either spans or
is to the right of the scrollRect's right edge. | LayoutBase | ||
Returns the bounds of the target's scroll rectangle in layout coordinates. | LayoutBase | ||
Called when the verticalScrollPosition or
horizontalScrollPosition properties change. | LayoutBase | ||
clipAndEnableScrolling | property |
clipAndEnableScrolling:Boolean| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
If true, specifies to clip the children to the boundaries of the viewport.
If false, the container children extend past the container boundaries,
regardless of the size specification of the component.
The default value is false.
Implementation
public function get clipAndEnableScrolling():Boolean public function set clipAndEnableScrolling(value:Boolean):voiddropIndicator | property |
dropIndicator:DisplayObject| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
The DisplayObject that this layout uses for
the drop indicator during a drag-and-drop operation.
Typically you do not set this property directly,
but instead define a dropIndicator skin part in the
skin class of the drop target.
The List control sets this property in response to a
DragEvent.DRAG_ENTER event.
The List initializes this property with an
instance of its dropIndicator skin part.
The List clears this property in response to a
DragEvent.DRAG_EXIT event.
Implementation
public function get dropIndicator():DisplayObject public function set dropIndicator(value:DisplayObject):voidhorizontalScrollPosition | property |
horizontalScrollPosition:Number| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
The x coordinate of the origin of the viewport in the component's coordinate system,
where the default value is (0,0) corresponding to the upper-left corner of the component.
If clipAndEnableScrolling is true, setting this property
typically causes the viewport to be set to:
new Rectangle(horizontalScrollPosition, verticalScrollPosition, width, height)
Implementations of this property must be Bindable and
must generate events of type propertyChange.
The default value is 0.
This property can be used as the source for data binding. When this property is modified, it dispatches the propertyChange event.
Implementation
public function get horizontalScrollPosition():Number public function set horizontalScrollPosition(value:Number):voidtarget | property |
target:GroupBase| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
The GroupBase container whose elements are measured, sized and positioned by this layout.
Subclasses may override the setter to perform target specific
actions. For example a 3D layout may set the target's
maintainProjectionCenter property here.
The default value is null.
Implementation
public function get target():GroupBase public function set target(value:GroupBase):voidRelated API Elements
typicalLayoutElement | property |
typicalLayoutElement:ILayoutElement| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Used by layouts when fixed row/column sizes are requested but a specific size isn't specified. Used by virtual layouts to estimate the size of layout elements that have not been scrolled into view.
This property references a component that Flex uses to define the height of all container children, as the following example shows:
<s:Group>
<s:layout>
<s:VerticalLayout variableRowHeight="false"
typicalLayoutElement="{b3}"/>
</s:layout>
<s:Button id="b1" label="Button 1"/>
<s:Button id="b2" label="Button 2"/>
<s:Button id="b3" label="Button 3" fontSize="36"/>
<s:Button id="b4" label="Button 4" fontSize="24"/>
</s:Group>
If this property has not been set and the target is non-null then the target's first layout element is cached and returned.
The default value is the target's first layout element.
The default value is null.
Implementation
public function get typicalLayoutElement():ILayoutElement public function set typicalLayoutElement(value:ILayoutElement):voidRelated API Elements
useVirtualLayout | property |
useVirtualLayout:Boolean| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
A container can hold any number of children. However, each child requires an instance of an item renderer. If the container has many children, you might notice performance degradation as you add more children to the container.
Instead of creating an item renderer for each child, you can configure the container to use a virtual layout. With virtual layout, the container reuses item renderers so that it only creates item renderers for the currently visible children of the container. As a child is moved off the screen, possible by scrolling the container, a new child being scrolled onto the screen can reuse its item renderer.
To configure a container to use virtual layout, set the useVirtualLayout property
to true for the layout associated with the container.
Only DataGroup or SkinnableDataContainer with layout set to VerticalLayout,
HorizontalLayout, or TileLayout supports virtual layout.
Layout subclasses that do not support virtualization must prevent changing
this property.
Note: The BasicLayout class throws a run-time error if you set
useVirtualLayout to true.
When true, layouts that support virtualization must use
the target.getVirtualElementAt() method,
rather than getElementAt(), and must only get the
elements they anticipate will be visible given the value of getScrollRect().
When true, the layout class must be able to compute
the indices of the layout elements that overlap the scrollRect in its
updateDisplayList() method based exclusively on cached information, not
by getting layout elements and examining their bounds.
Typically virtual layouts update their cached information
in the updateDisplayList() method,
based on the sizes and locations computed for the elements in view.
Similarly, in the measure() method, virtual layouts should update the target's
measured size properties based on the typicalLayoutElement and other
cached layout information, not by measuring elements.
Containers cooperate with layouts that have useVirtualLayout = true by
recycling item renderers that were previously constructed, but are no longer in use.
An item is considered to be no longer in use if its index is not
within the range of getVirtualElementAt() indices requested during
the container's most recent updateDisplayList() invocation.
The default value is false.
Implementation
public function get useVirtualLayout():Boolean public function set useVirtualLayout(value:Boolean):voidRelated API Elements
verticalScrollPosition | property |
verticalScrollPosition:Number| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
The y coordinate of the origin of the viewport in the component's coordinate system,
where the default value is (0,0) corresponding to the upper-left corner of the component.
If clipAndEnableScrolling is true, setting this property
typically causes the viewport to be set to:
new Rectangle(horizontalScrollPosition, verticalScrollPosition, width, height)
Implementations of this property must be Bindable and
must generate events of type propertyChange.
The default value is 0.
This property can be used as the source for data binding. When this property is modified, it dispatches the propertyChange event.
Implementation
public function get verticalScrollPosition():Number public function set verticalScrollPosition(value:Number):voidLayoutBase | () | Constructor |
public function LayoutBase()| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Constructor.
calculateDragScrollDelta | () | method |
protected function calculateDragScrollDelta(dropLocation:DropLocation, elapsedTime:Number):Point| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Calculates how much to scroll for the specified dropLocation
during a drag and drop gesture.
Called by the showDropIndicator() method to calculate the scroll
during drag-scrolling.
Parameters
dropLocation:DropLocation — A valid DropLocation object previously obtained
by calling the calculateDropLocation() method.
| |
elapsedTime:Number — The duration, in milliseconds, since the drag scrolling start.
|
Point — How much to drag scroll, or null if drag-scrolling is not needed.
|
Related API Elements
calculateDropIndex | () | method |
protected function calculateDropIndex(x:Number, y:Number):int| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the index where a new item should be inserted if
the user releases the mouse at the specified coordinates
while completing a drag and drop gesture.
Called by the calculatedDropLocation() method.
Parameters
x:Number — The x coordinate of the drag and drop gesture, in
local coordinates.
| |
y:Number — The y coordinate of the drag and drop gesture, in
the drop target's local coordinates.
|
int — The drop index or -1 if the drop operation is not available
at the specified coordinates.
|
Related API Elements
calculateDropIndicatorBounds | () | method |
protected function calculateDropIndicatorBounds(dropLocation:DropLocation):Rectangle| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Calculates the bounds for the drop indicator that provides visual feedback
to the user of where the items will be inserted at the end of a drag and drop
gesture.
Called by the showDropIndicator() method.
Parameters
dropLocation:DropLocation — A valid DropLocation object previously returned
by the calculateDropLocation() method.
|
Rectangle — The bounds for the drop indicator or null.
|
Related API Elements
calculateDropLocation | () | method |
public function calculateDropLocation(dragEvent:DragEvent):DropLocation| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Calculates the drop location in the data provider of the drop target for
the specified dragEvent.
Parameters
dragEvent:DragEvent — The drag event dispatched by the DragManager.
|
DropLocation — Returns the drop location for this event, or null if the drop
operation is not available.
|
Related API Elements
clearVirtualLayoutCache | () | method |
public function clearVirtualLayoutCache():void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
When useVirtualLayout is true,
this method can be used by the layout target
to clear cached layout information when the target changes.
For example, when a DataGroup's dataProvider or
itemRenderer property changes, cached
elements sizes become invalid.
When the useVirtualLayout property changes to false,
this method is called automatically.
Subclasses that support useVirtualLayout = true
must override this method.
elementAdded | () | method |
public function elementAdded(index:int):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Called by the target after a layout element has been added and before the target's size and display list are validated. Layouts that cache per element state, like virtual layouts, can override this method to update their cache.
If the target calls this method, it's only guaranteeing that a
a layout element will exist at the specified index at
updateDisplayList() time, for example a DataGroup
with a virtual layout will call this method when an item is added
to the targets dataProvider.
By default, this method does nothing.
Parameters
index:int — The index of the element that was added.
|
Related API Elements
elementRemoved | () | method |
public function elementRemoved(index:int):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
This method must is called by the target after a layout element has been removed and before the target's size and display list are validated. Layouts that cache per element state, like virtual layouts, can override this method to update their cache.
If the target calls this method, it's only guaranteeing that a
a layout element will no longer exist at the specified index at
updateDisplayList() time.
For example, a DataGroup
with a virtual layout calls this method when an item is added to
the dataProvider property.
By default, this method does nothing.
Parameters
index:int — The index of the element that was added.
|
Related API Elements
getElementBounds | () | method |
public function getElementBounds(index:int):Rectangle| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the specified element's layout bounds as a Rectangle or null
if the index is invalid, the corresponding element is null,
includeInLayout=false,
or if this layout's target property is null.
Layout subclasses that support useVirtualLayout=true must
override this method to compute a potentially approximate value for
elements that are not in view.
Parameters
index:int — Index of the layout element.
|
Rectangle — The specified element's layout bounds.
|
Related API Elements
getElementBoundsAboveScrollRect | () | method |
protected function getElementBoundsAboveScrollRect(scrollRect:Rectangle):Rectangle| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the bounds of the first layout element that either spans or is above the scrollRect's top edge.
This is a convenience method that is used by the default
implementation of the getVerticalScrollPositionDelta() method.
Subclasses that rely on the default implementation of
getVerticalScrollPositionDelta() should override this method to
provide an accurate bounding rectangle that has valid top and
bottom properties.
By default this method returns a Rectangle with width=0, height=1,
whose top edge is one less than the top edge of the scrollRect,
and left=0.
Subclasses should override this method to provide an accurate
bounding rectangle that has valid top and
bottom properties.
Parameters
scrollRect:Rectangle — The target's scrollRect.
|
Rectangle — The bounds of the first element that spans or is
above the scrollRect's top edge.
|
Related API Elements
getElementBoundsBelowScrollRect | () | method |
protected function getElementBoundsBelowScrollRect(scrollRect:Rectangle):Rectangle| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the bounds of the first layout element that either spans or is below the scrollRect's bottom edge.
This is a convenience method that is used by the default
implementation of the getVerticalScrollPositionDelta() method.
Subclasses that rely on the default implementation of
getVerticalScrollPositionDelta() should override this method to
provide an accurate bounding rectangle that has valid top and
bottom properties.
By default this method returns a Rectangle with width=0, height=1,
whose bottom edge is one more than the bottom edge of the scrollRect,
and left=0.
Parameters
scrollRect:Rectangle — The target's scrollRect.
|
Rectangle — The bounds of the first element that spans or is
below the scrollRect's bottom edge.
|
Related API Elements
getElementBoundsLeftOfScrollRect | () | method |
protected function getElementBoundsLeftOfScrollRect(scrollRect:Rectangle):Rectangle| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the bounds of the first layout element that either spans or is to the left of the scrollRect's left edge.
This is a convenience method that is used by the default
implementation of the getHorizontalScrollPositionDelta() method.
Subclasses that rely on the default implementation of
getHorizontalScrollPositionDelta() should override this method to
provide an accurate bounding rectangle that has valid left and
right properties.
By default this method returns a Rectangle with width=1, height=0,
whose left edge is one less than the left edge of the scrollRect,
and top=0.
Parameters
scrollRect:Rectangle — The target's scrollRect.
|
Rectangle — The bounds of the first element that spans or is to
the left of the scrollRect's left edge.
|
Related API Elements
getElementBoundsRightOfScrollRect | () | method |
protected function getElementBoundsRightOfScrollRect(scrollRect:Rectangle):Rectangle| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the bounds of the first layout element that either spans or is to the right of the scrollRect's right edge.
This is a convenience method that is used by the default
implementation of the getHorizontalScrollPositionDelta() method.
Subclasses that rely on the default implementation of
getHorizontalScrollPositionDelta() should override this method to
provide an accurate bounding rectangle that has valid left and
right properties.
By default this method returns a Rectangle with width=1, height=0,
whose right edge is one more than the right edge of the scrollRect,
and top=0.
Parameters
scrollRect:Rectangle — The target's scrollRect.
|
Rectangle — The bounds of the first element that spans or is to
the right of the scrollRect's right edge.
|
Related API Elements
getHorizontalScrollPositionDelta | () | method |
public function getHorizontalScrollPositionDelta(navigationUnit:uint):Number| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the change to the horizontal scroll position to handle
different scrolling options.
These options are defined by the NavigationUnit class: END, HOME,
LEFT, PAGE_LEFT, PAGE_RIGHT, and RIGHT.
Parameters
navigationUnit:uint — Takes the following values:
The implementation calls |
Number — The change to the horizontal scroll position.
|
Related API Elements
getNavigationDestinationIndex | () | method |
public function getNavigationDestinationIndex(currentIndex:int, navigationUnit:uint, arrowKeysWrapFocus:Boolean):int| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Delegation method that determines which item to navigate to based on the current item in focus and user input in terms of NavigationUnit. This method is used by subclasses of ListBase to handle keyboard navigation. ListBase maps user input to NavigationUnit constants.
Subclasses can override this method to compute other values that are based on the current index and key stroke encountered.
Parameters
currentIndex:int — The current index of the item with focus.
| |
navigationUnit:uint — The NavigationUnit constant that determines
which item to navigate to next.
| |
arrowKeysWrapFocus:Boolean — If true, using arrow keys to
navigate within the component wraps when it hits either end.
|
int — The index of the next item to jump to. Returns -1
when if the layout doesn't recognize the navigationUnit.
|
getScrollPositionDeltaToElement | () | method |
public function getScrollPositionDeltaToElement(index:int):Point| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Computes the verticalScrollPosition and
horizontalScrollPosition deltas needed to
scroll the element at the specified index into view.
This method attempts to minimize the change to verticalScrollPosition
and horizontalScrollPosition.
If clipAndEnableScrolling is true
and the element at the specified index is not
entirely visible relative to the target's scroll rectangle, then
return the delta to be added to horizontalScrollPosition and
verticalScrollPosition that scrolls the element completely
within the scroll rectangle's bounds.
Parameters
index:int — The index of the element to be scrolled into view.
|
Point — A Point that contains offsets to horizontalScrollPosition
and verticalScrollPosition that will scroll the specified
element into view, or null if no change is needed.
If the specified element is partially visible and larger than the
scroll rectangle, meaning it is already the only element visible, then
return null.
If the specified index is invalid, or target is null, then
return null.
If the element at the specified index is null or includeInLayout
false, then return null.
|
Related API Elements
getScrollRect | () | method |
protected function getScrollRect():Rectangle| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the bounds of the target's scroll rectangle in layout coordinates. Layout methods should not get the target's scroll rectangle directly.
ReturnsRectangle — The bounds of the target's scrollRect in layout coordinates, null
if target or clipAndEnableScrolling is false.
|
getVerticalScrollPositionDelta | () | method |
public function getVerticalScrollPositionDelta(navigationUnit:uint):Number| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Returns the change to the vertical scroll position to handle
different scrolling options.
These options are defined by the NavigationUnit class:
DOWN, END, HOME,
PAGE_DOWN, PAGE_UP, and UP.
Parameters
navigationUnit:uint — Takes the following values:
PAGE_UPThe implementation calls |
Number — The change to the vertical scroll position.
|
Related API Elements
hideDropIndicator | () | method |
public function hideDropIndicator():void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Hides the previously shown drop indicator,
created by the showDropIndicator() method,
removes it from the display list and also stops the drag scrolling.
Related API Elements
measure | () | method |
public function measure():void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Measures the target's default size based on its content, and optionally measures the target's default minimum size.
This is one of the methods that you must override when creating a
subclass of LayoutBase. The other method is updateDisplayList().
You do not call these methods directly. Flex calls this method as part
of a layout pass. A layout pass consists of three phases.
First, if the target's properties are invalid, the LayoutManager calls
the target's commitProperties method.
Second, if the target's size is invalid, LayoutManager calls the target's
validateSize() method. The target's validateSize()
will in turn call the layout's measure() to calculate the
target's default size unless it was explicitly specified by both target's
explicitWidth and explicitHeight properties.
If the default size changes, Flex will invalidate the target's display list.
Last, if the target's display list is invalid, LayoutManager calls the target's
validateDisplayList. The target's validateDisplayList
will in turn call the layout's updateDisplayList method to
size and position the target's elements.
When implementing this method, you must set the target's
measuredWidth and measuredHeight properties
to define the target's default size. You may optionally set the
measuredMinWidth and measuredMinHeight
properties to define the default minimum size.
A typical implementation iterates through the target's elements
and uses the methods defined by the ILayoutElement to
accumulate the preferred and/or minimum sizes of the elements and then sets
the target's measuredWidth, measuredHeight,
measuredMinWidth and measuredMinHeight.
Related API Elements
scrollPositionChanged | () | method |
protected function scrollPositionChanged():void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Called when the verticalScrollPosition or
horizontalScrollPosition properties change.
The default implementation updates the target's scrollRect property by
calling updateScrollRect().
Subclasses can override this method to compute other values that are
based on the current scrollPosition or scrollRect.
Related API Elements
showDropIndicator | () | method |
public function showDropIndicator(dropLocation:DropLocation):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Sizes, positions and parents the drop indicator based on the specified
drop location. Use the calculateDropLocation() method
to obtain the DropLocation object.
Starts/stops drag-scrolling when necessary conditions are met.
Parameters
dropLocation:DropLocation — Specifies the location where to show the drop indicator.
Drop location is obtained through the computeDropLocation() method.
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Related API Elements
updateDisplayList | () | method |
public function updateDisplayList(width:Number, height:Number):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Sizes and positions the target's elements.
This is one of the methods that you must override when creating a
subclass of LayoutBase. The other method is measure().
You do not call these methods directly. Flex calls this method as part
of a layout pass. A layout pass consists of three phases.
First, if the target's properties are invalid, the LayoutManager calls
the target's commitProperties method.
Second, if the target's size is invalid, LayoutManager calls the target's
validateSize() method. The target's validateSize()
will in turn call the layout's measure() to calculate the
target's default size unless it was explicitly specified by both target's
explicitWidth and explicitHeight properties.
If the default size changes, Flex will invalidate the target's display list.
Last, if the target's display list is invalid, LayoutManager calls the target's
validateDisplayList. The target's validateDisplayList
will in turn call the layout's updateDisplayList method to
size and position the target's elements.
A typical implementation iterates through the target's elements
and uses the methods defined by the ILayoutElement to
position and resize the elements. Then the layout must also calculate and set
the target's contentWidth and contentHeight
properties to define the target's scrolling region.
Parameters
width:Number — Specifies the width of the target, in pixels,
in the targets's coordinates.
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height:Number — Specifies the height of the component, in pixels,
in the target's coordinates.
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Related API Elements
updateScrollRect | () | method |
public function updateScrollRect(w:Number, h:Number):void| Language Version: | ActionScript 3.0 |
| Product Version: | Flex 4 |
| Runtime Versions: | Flash Player 10, AIR 1.5 |
Called by the target at the end of its updateDisplayList
to have the layout update its scrollRect.
If clipAndEnableScrolling is true,
the default implementation sets the origin of the target's scrollRect
to verticalScrollPosition, horizontalScrollPosition.
It sets its size to the width, height
parameters (the target's unscaled width and height).
If clipAndEnableScrolling is false,
the default implementation sets the scrollRect to null.
Parameters
w:Number — The target's width.
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h:Number — The target's height.
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Related API Elements
Wed Nov 21 2018, 06:34 AM -08:00