mx.effects.Tween - Adobe® Flex® 4 Language Reference (Flex 4)

Package	mx.effects
Class	public class Tween
Inheritance	Tween EventDispatcher Object

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Starting with Flex 4.0, Adobe recommends that you use the spark.effects.animation.Animation class as an alternative to this class.

Tween is the underlying animation class for the effects in Flex 3. As of Flex 4, the Spark effects use the spark.effects.animation.Animation class to provide similar functionality.

The Tween class defines a tween, a property animation performed on a target object over a period of time. That animation can be a change in position, such as performed by the Move effect; a change in size, as performed by the Resize or Zoom effects; a change in visibility, as performed by the Fade or Dissolve effects; or other types of animations.

When defining tween effects, you typically create an instance of the Tween class within your override of the EffectInstance.play() method. A Tween instance accepts the startValue, endValue, and duration properties, and an optional easing function to define the animation.

The Tween object invokes the mx.effects.effectClasses.TweenEffectInstance.onTweenUpdate() callback function on a regular interval on the effect instance for the duration of the effect, passing to the onTweenUpdate() method an interpolated value between the startValue and endValue. Typically, the callback function updates some property of the target object, causing that object to animate over the duration of the effect.

When the effect ends, the Tween objects invokes the mx.effects.effectClasses.TweenEffectInstance.onTweenEnd() callback function, if you defined one.

Public Properties

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	Property		Defined By
		constructor : Object A reference to the class object or constructor function for a given object instance.	Object
		duration : Number = 3000 Duration of the animation, in milliseconds.	Tween
		easingFunction : Function [write-only] Sets the easing function for the animation.	Tween
		listener : Object Object that is notified at each interval of the animation.	Tween
		prototype : Object [static] A reference to the prototype object of a class or function object.	Object

Public Methods

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	Method		Defined By
		Tween(listener:Object, startValue:Object, endValue:Object, duration:Number = -1, minFps:Number = -1, updateFunction:Function = null, endFunction:Function = null) Constructor.	Tween
		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.	EventDispatcher
		dispatchEvent(event:Event):Boolean Dispatches an event into the event flow.	EventDispatcher
		endTween():void Interrupt the tween, jump immediately to the end of the tween, and invoke the onTweenEnd() callback function.	Tween
		hasEventListener(type:String):Boolean Checks whether the EventDispatcher object has any listeners registered for a specific type of event.	EventDispatcher
		hasOwnProperty(name:String):Boolean Indicates whether an object has a specified property defined.	Object
		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
		pause():void Pauses the effect until you call the resume() method.	Tween
		propertyIsEnumerable(name:String):Boolean Indicates whether the specified property exists and is enumerable.	Object
		removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void Removes a listener from the EventDispatcher object.	EventDispatcher
		resume():void Resumes the effect after it has been paused by a call to the pause() method.	Tween
		reverse():void Plays the effect in reverse, starting from the current position of the effect.	Tween
		seek(playheadTime:Number):void Advances the tween effect to the specified position.	Tween
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Sets the availability of a dynamic property for loop operations.	Object
		setTweenHandlers(updateFunction:Function, endFunction:Function):void By default, the Tween class invokes the mx.effects.effectClasses.TweenEffectInstance.onTweenUpdate() callback function on a regular interval on the effect instance for the duration of the effect, and the optional mx.effects.effectClasses.TweenEffectInstance.onTweenEnd() callback function at the end of the effect duration.	Tween
		stop():void Stops the tween, ending it without dispatching an event or calling the Tween's endFunction or onTweenEnd().	Tween
		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
		valueOf():Object Returns the primitive value of the specified object.	Object
		willTrigger(type:String):Boolean Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type.	EventDispatcher

Events

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	Event		Summary	Defined By
		activate	[broadcast event] Dispatched when the Flash Player or AIR application gains operating system focus and becomes active.	EventDispatcher
		deactivate	[broadcast event] Dispatched when the Flash Player or AIR application operating loses system focus and is becoming inactive.	EventDispatcher

Property Detail

duration

property

public var duration:Number = 3000

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Duration of the animation, in milliseconds.

easingFunction

property

easingFunction:Function [write-only]

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Sets the easing function for the animation. The easing function is used to interpolate between the startValue value and the endValue. A trivial easing function does linear interpolation, but more sophisticated easing functions create the illusion of acceleration and deceleration, which makes the animation seem more natural.

If no easing function is specified, an easing function based on the Math.sin() method is used.

The easing function follows the function signature popularized by Robert Penner. The function accepts four arguments. The first argument is the "current time", where the animation start time is 0. The second argument is a the initial value at the beginning of the animation (a Number). The third argument is the ending value minus the initial value. The fourth argument is the duration of the animation. The return value is the interpolated value for the current time (usually a value between the initial value and the ending value).

Flex includes a set of easing functions in the mx.effects.easing package.

Implementation
public function set easingFunction(value:Function):void

listener

property

public var listener:Object

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Object that is notified at each interval of the animation.

Constructor Detail

Tween

()

Constructor

public function Tween(listener:Object, startValue:Object, endValue:Object, duration:Number = -1, minFps:Number = -1, updateFunction:Function = null, endFunction:Function = null)

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Constructor.

When the constructor is called, the animation automatically starts playing.

Parameters

	`listener:Object` — Object that is notified at each interval of the animation. You typically pass the `this` keyword as the value. The `listener` must define the `onTweenUpdate()` method and optionally the `onTweenEnd()` method. The former method is invoked for each interval of the animation, and the latter is invoked just after the animation finishes.

	`startValue:Object` — Initial value(s) of the animation. Either a number or an array of numbers. If a number is passed, the Tween interpolates between this number and the number passed in the `endValue` parameter. If an array of numbers is passed, each number in the array is interpolated.

	`endValue:Object` — Final value(s) of the animation. The type of this argument must match the `startValue` parameter.

	`duration:Number` (default = `-1`) — Duration of the animation, expressed in milliseconds.

	`minFps:Number` (default = `-1`) — Minimum number of times that the `onTweenUpdate()` method should be called every second. The tween code tries to call the `onTweenUpdate()` method as frequently as possible (up to 100 times per second). However, if the frequency falls below `minFps`, the duration of the animation automatically increases. As a result, an animation that temporarily freezes (because it is not getting any CPU cycles) begins again where it left off, instead of suddenly jumping ahead.

	`updateFunction:Function` (default = `null`) — Specifies an alternative update callback function to be used instead of `listener.OnTweenUpdate()`

	`endFunction:Function` (default = `null`) — Specifies an alternative end callback function to be used instead of `listener.OnTweenEnd()`

Method Detail

endTween

()

method

public function endTween():void

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Interrupt the tween, jump immediately to the end of the tween, and invoke the onTweenEnd() callback function.

pause

()

method

public function pause():void

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Pauses the effect until you call the resume() method.

resume

()

method

public function resume():void

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Resumes the effect after it has been paused by a call to the pause() method.

reverse

()

method

public function reverse():void

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Plays the effect in reverse, starting from the current position of the effect.

seek

()

method

public function seek(playheadTime:Number):void

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Advances the tween effect to the specified position.

Parameters

playheadTime:Number — The position, in milliseconds, between 0 and the value of the duration property.

setTweenHandlers

()

method

public function setTweenHandlers(updateFunction:Function, endFunction:Function):void

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

By default, the Tween class invokes the mx.effects.effectClasses.TweenEffectInstance.onTweenUpdate() callback function on a regular interval on the effect instance for the duration of the effect, and the optional mx.effects.effectClasses.TweenEffectInstance.onTweenEnd() callback function at the end of the effect duration.

This method lets you specify different methods as the update and the end callback functions.

Parameters

	`updateFunction:Function` — Specifies the update callback function.

	`endFunction:Function` — Specifies the end callback function.

stop

()

method

public function stop():void

Language Version:

ActionScript 3.0

Product Version:

Flex 3

Runtime Versions:

Flash Player 9, AIR 1.1

Stops the tween, ending it without dispatching an event or calling the Tween's endFunction or onTweenEnd().