spark.layouts.HorizontalLayout - Adobe® Flex® 4 Language Reference (Flex 4)

Package	spark.layouts
Class	public class HorizontalLayout
Inheritance	HorizontalLayout LayoutBase OnDemandEventDispatcher Object

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The HorizontalLayout class arranges the layout elements in a horizontal sequence, left to right, with optional gaps between the elements and optional padding around the elements.

The horizontal position of the elements is determined by arranging them in a horizontal sequence, left to right, taking into account the padding before the first element and the gaps between the elements.

The vertical position of the elements is determined by the layout's verticalAlign property.

During the execution of the measure() method, the default size of the container is calculated by accumulating the preferred sizes of the elements, including gaps and padding. When the requestedColumnCount property is set to a value other than -1, only the space for that many elements is measured, starting from the first element.

During the execution of the updateDisplayList() method, the width of each element is calculated according to the following rules, listed in their respective order of precedence (element's minimum width and maximum width are always respected):

If variableColumnWidth is false, then set the element's width to the value of the columnWidth property.
If the element's percentWidth is set, then calculate the element's width by distributing the available container width between all elements with percentWidth setting. The available container width is equal to the container width minus the gaps, the padding and the space occupied by the rest of the elements. The element's precentWidth property is ignored when the layout is virtualized.
Set the element's width to its preferred width.

The height of each element is calculated according to the following rules, listed in their respective order of precedence (element's minimum height and maximum height are always respected):

If the verticalAlign property is "justify", then set the element's height to the container height.
If the verticalAlign property is "contentJustify", then set the element's height to the maximum between the container's height and all elements' preferred height.
If the element's percentHeight property is set, then calculate the element's height as a percentage of the container's height.
Set the element's height to its preferred height.

MXML Syntax expanded

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The <s:HorizontalLayout> tag inherits all of the tag attributes of its superclass and adds the following tag attributes:

  <s:HorizontalLayout 
    Properties
    columnWidth="calculated"
    gap="6"
    paddingBottom="0"
    paddingLeft="0"
    paddingRight="0"
    paddingTop="0"
    requestedColumnCount="-1"
    requestedMinColumnCount="-1"
    variableColumnWidth="true"
    verticalAlign="top"
  />

Public Properties

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	Property		Defined By
		clipAndEnableScrolling : Boolean If true, specifies to clip the children to the boundaries of the viewport.	LayoutBase
		columnCount : int [read-only] Returns the current number of elements in view.	HorizontalLayout
		columnWidth : Number If the variableColumnWidth property is false, then this property specifies the actual width of each layout element, in pixels.	HorizontalLayout
		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
		firstIndexInView : int [read-only] The index of the first column that is part of the layout and within the layout target's scroll rectangle, or -1 if nothing has been displayed yet.	HorizontalLayout
		gap : int The horizontal space between layout elements, in pixels.	HorizontalLayout
		horizontalAlign : String The horizontal alignment of the content relative to the container's width.	HorizontalLayout
		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
		lastIndexInView : int [read-only] The index of the last column that is part of the layout and within the layout target's scroll rectangle, or -1 if nothing has been displayed yet.	HorizontalLayout
		paddingBottom : Number The minimum number of pixels between the container's bottom edge and the bottom of all the container's layout elements.	HorizontalLayout
		paddingLeft : Number Number of pixels between the container's left edge and the left edge of the first layout element.	HorizontalLayout
		paddingRight : Number Number of pixels between the container's right edge and the right edge of the last layout element.	HorizontalLayout
		paddingTop : Number The minimum number of pixels between the container's top edge and the top of all the container's layout elements.	HorizontalLayout
		prototype : Object [static] A reference to the prototype object of a class or function object.	Object
		requestedColumnCount : int The measured size of this layout is wide enough to display the first requestedColumnCount layout elements.	HorizontalLayout
		requestedMinColumnCount : int The measured width of this layout is large enough to display at least requestedMinColumnCount layout elements.	HorizontalLayout
		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
		variableColumnWidth : Boolean If true, specifies that layout elements are to be allocated their preferred width.	HorizontalLayout
		verticalAlign : String The vertical alignment of layout elements.	HorizontalLayout
		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

Public Methods

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	Method		Defined By
		HorizontalLayout() Constructor.	HorizontalLayout
		addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void	OnDemandEventDispatcher
		calculateDropLocation(dragEvent:DragEvent):DropLocation Calculates the drop location in the data provider of the drop target for the specified dragEvent.	LayoutBase
		clearVirtualLayoutCache():void When useVirtualLayout is true, this method can be used by the layout target to clear cached layout information when the target changes.	LayoutBase
		dispatchEvent(event:Event):Boolean	OnDemandEventDispatcher
		elementAdded(index:int):void Called by the target after a layout element has been added and before the target's size and display list are validated.	LayoutBase
		elementRemoved(index:int):void 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
		fractionOfElementInView(index:int):Number Returns 1.0 if the specified index is completely in view, 0.0 if it's not, or a value between 0.0 and 1.0 that represents the percentage of the if the index that is partially in view.	HorizontalLayout
		getElementBounds(index:int):Rectangle 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
		getHorizontalScrollPositionDelta(navigationUnit:uint):Number 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
		getScrollPositionDeltaToElement(index:int):Point Computes the verticalScrollPosition and horizontalScrollPosition deltas needed to scroll the element at the specified index into view.	LayoutBase
		getVerticalScrollPositionDelta(navigationUnit:uint):Number Returns the change to the horizontal scroll position to handle different scrolling options.	LayoutBase
		hasEventListener(type:String):Boolean	OnDemandEventDispatcher
		hasOwnProperty(name:String):Boolean Indicates whether an object has a specified property defined.	Object
		hideDropIndicator():void Hides the previously shown drop indicator, created by the showDropIndicator() method, removes it from the display list and also stops the drag scrolling.	LayoutBase
		isPrototypeOf(theClass:Object):Boolean Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.	Object
		measure():void Measures the target's default size based on its content, and optionally measures the target's default minimum size.	LayoutBase
		propertyIsEnumerable(name:String):Boolean Indicates whether the specified property exists and is enumerable.	Object
		removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void	OnDemandEventDispatcher
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Sets the availability of a dynamic property for loop operations.	Object
		showDropIndicator(dropLocation:DropLocation):void Sizes, positions and parents the drop indicator based on the specified drop location.	LayoutBase
		toLocaleString():String Returns the string representation of this object, formatted according to locale-specific conventions.	Object
		toString():String Returns the string representation of the specified object.	Object
		updateDisplayList(width:Number, height:Number):void Sizes and positions the target's elements.	LayoutBase
		updateScrollRect(w:Number, h:Number):void Called by the target at the end of its updateDisplayList to have the layout update its scrollRect.	LayoutBase
		valueOf():Object Returns the primitive value of the specified object.	Object
		willTrigger(type:String):Boolean	OnDemandEventDispatcher

Protected Methods

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	Method		Defined By
		calculateDragScrollDelta(dropLocation:DropLocation, elapsedTime:Number):Point Calculates how much to scroll for the specified dropLocation during a drag and drop gesture.	LayoutBase
		calculateDropIndex(x:Number, y:Number):int 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
		calculateDropIndicatorBounds(dropLocation:DropLocation):Rectangle 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
		getElementBoundsAboveScrollRect(scrollRect:Rectangle):Rectangle Returns the bounds of the first layout element that either spans or is above the scrollRect's top edge.	LayoutBase
		getElementBoundsBelowScrollRect(scrollRect:Rectangle):Rectangle Returns the bounds of the first layout element that either spans or is below the scrollRect's bottom edge.	LayoutBase
		getElementBoundsLeftOfScrollRect(scrollRect:Rectangle):Rectangle Returns the bounds of the first layout element that either spans or is to the left of the scrollRect's left edge.	LayoutBase
		getElementBoundsRightOfScrollRect(scrollRect:Rectangle):Rectangle Returns the bounds of the first layout element that either spans or is to the right of the scrollRect's right edge.	LayoutBase
		getScrollRect():Rectangle Returns the bounds of the target's scroll rectangle in layout coordinates.	LayoutBase
		scrollPositionChanged():void Called when the verticalScrollPosition or horizontalScrollPosition properties change.	LayoutBase

Property Detail

columnCount

property

columnCount:int [read-only]

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

Returns the current number of elements in view.

The default value is -1.

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 columnCount():int

columnWidth

property

columnWidth:Number

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

If the variableColumnWidth property is false, then this property specifies the actual width of each layout element, in pixels.

If the variableColumnWidth property is true, the default, then this property has no effect.

The default value of this property is the preferred width of the item specified by the typicalLayoutElement property.

Implementation
public function get columnWidth():Number
public function set columnWidth(value:Number):void

firstIndexInView

property

firstIndexInView:int [read-only]

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The index of the first column that is part of the layout and within the layout target's scroll rectangle, or -1 if nothing has been displayed yet. Note that the column may only be partially in view.

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

Implementation
public function get firstIndexInView():int

gap

property

gap:int

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The horizontal space between layout elements, in pixels. Note that the gap is only applied between layout elements, so if there's just one element, the gap has no effect on the layout.

The default value is 6.

Implementation
public function get gap():int
public function set gap(value:int):void

horizontalAlign

property

horizontalAlign:String

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The horizontal alignment of the content relative to the container's width. If the value is "left", "right", or "center" then the layout element is aligned relative to the container's contentWidth property.

If the value is "contentJustify", then the layout element's actual width is set to the contentWidth of the container. The contentWidth of the container is the width of the largest layout element. If all layout elements are smaller than the width of the container, then set the width of all layout elements to the width of the container.

If the value is "justify" then the layout element's actual width is set to the container's width.

This property has no effect when clipAndEnableScrolling is true and the contentWidth is greater than the container's width.

This property does not affect the layout's measured size.

The default value is "left".

Implementation
public function get horizontalAlign():String
public function set horizontalAlign(value:String):void

lastIndexInView

property

lastIndexInView:int [read-only]

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The index of the last column that is part of the layout and within the layout target's scroll rectangle, or -1 if nothing has been displayed yet. Note that the column may only be partially in view.

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

Implementation
public function get lastIndexInView():int

paddingBottom

property

paddingBottom:Number

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The minimum number of pixels between the container's bottom edge and the bottom of all the container's layout elements.

The default value is 0.

Implementation
public function get paddingBottom():Number
public function set paddingBottom(value:Number):void

paddingLeft

property

paddingLeft:Number

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

Number of pixels between the container's left edge and the left edge of the first layout element.

The default value is 0.

Implementation
public function get paddingLeft():Number
public function set paddingLeft(value:Number):void

paddingRight

property

paddingRight:Number

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

Number of pixels between the container's right edge and the right edge of the last layout element.

The default value is 0.

Implementation
public function get paddingRight():Number
public function set paddingRight(value:Number):void

paddingTop

property

paddingTop:Number

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The minimum number of pixels between the container's top edge and the top of all the container's layout elements.

The default value is 0.

Implementation
public function get paddingTop():Number
public function set paddingTop(value:Number):void

requestedColumnCount

property

requestedColumnCount:int

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The measured size of this layout is wide enough to display the first requestedColumnCount layout elements. If requestedColumnCount is -1, then the measured size will be big enough for all of the layout elements.

If the actual size of the container using this layout has been explicitly set, then this property has no effect.

The default value is -1.

Implementation
public function get requestedColumnCount():int
public function set requestedColumnCount(value:int):void

requestedMinColumnCount

property

requestedMinColumnCount:int

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The measured width of this layout is large enough to display at least requestedMinColumnCount layout elements.

If requestedColumnCount is set, then this property has no effect.

If the actual size of the container using this layout has been explicitly set, then this property has no effect.

The default value is -1.

Implementation
public function get requestedMinColumnCount():int
public function set requestedMinColumnCount(value:int):void

variableColumnWidth

property

variableColumnWidth:Boolean

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

If true, specifies that layout elements are to be allocated their preferred width.

Setting this property to false specifies fixed width columns. The actual width of each layout element is the value of the columnWidth property, and the layout ignores a layout elements' percentWidth property.

The default value is true.

Implementation
public function get variableColumnWidth():Boolean
public function set variableColumnWidth(value:Boolean):void

verticalAlign

property

verticalAlign:String

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

The vertical alignment of layout elements.

If the value is "bottom", "middle", or "top" then the layout elements are aligned relative to the container's contentHeight property.

If the value is "contentJustify" then the actual height of the layout element is set to the container's contentHeight property. The content height of the container is the height of the largest layout element. If all layout elements are smaller than the height of the container, then set the height of all the layout elements to the height of the container.

If the value is "justify" then the actual height of the layout elements is set to the container's height.

This property does not affect the layout's measured size.

The default value is "top".

Implementation
public function get verticalAlign():String
public function set verticalAlign(value:String):void

Constructor Detail

HorizontalLayout

()

Constructor

public function HorizontalLayout()

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

Constructor.

Method Detail

fractionOfElementInView

()

method

public function fractionOfElementInView(index:int):Number

Language Version:

ActionScript 3.0

Product Version:

Flex 4

Runtime Versions:

Flash Player 10, AIR 1.5

Returns 1.0 if the specified index is completely in view, 0.0 if it's not, or a value between 0.0 and 1.0 that represents the percentage of the if the index that is partially in view.

An index is "in view" if the corresponding non-null layout element is within the horizontal limits of the container's scrollRect and included in the layout.

If the specified index is partially within the view, the returned value is the percentage of the corresponding layout element that's visible.

Parameters

index:int — The index of the column.

Returns

Number — The percentage of the specified element that's in view. Returns 0.0 if the specified index is invalid or if it corresponds to null element, or a ILayoutElement for which the includeInLayout property is false.