tween_class.as

来自「这是《Flash MX编程与创意实现》的源代码」· AS 代码 · 共 125 行

/*
  Tween Class v1.2
  Oct. 29, 2002
  (c) 2002 Robert Penner
  
  The Tween class provides a versatile framework
  for dynamic motion tweening with ActionScript.
  
  Dependencies: 
  - Motion class 
  - Object.superCon() (found in core_setup.as)
  - Function.extend() (found in core_setup.as)
  - Penner easing equations (easing_equations.as)
    (strictly speaking, these equations are not mandatory; however, they are usually used with Tween)
  
  Events:
  
  	onMotionChanged
  	onMotionFinished
  	onMotionLooped
  	onMotionStarted
  	onMotionStopped
  	onMotionResumed
  
  Discussed in Chapter 7 of 
  Robert Penner's Programming Macromedia Flash MX
  
  http://www.robertpenner.com/profmx
  http://www.amazon.com/exec/obidos/ASIN/0072223561/robertpennerc-20
*/

if (typeof _global.Motion != 'function') trace (">> Error: superclass missing - Motion");
if (typeof Object.superCon != 'function') trace (">> Error: Object.superCon() missing (core_setup.as)");
 
/*  constructor for Tween class

	obj: reference - the object to which the Tween is targetted
	prop: string - the property (of obj) that will be affected
	func: reference - a function that calculates a position at a certain time
	begin: number - the value of prop at the start of the tween
	finish: number - the value of prop when the tween finishes
	duration: number - the length of time of the motion; set to infinity if negative or omitted
	useSeconds: boolean - a flag specifying whether to use seconds instead of frames
*/

_global.Tween = function (obj, prop, func, begin, finish, duration, useSeconds) {
	this.superCon (obj, prop, begin, duration, useSeconds);
	this.setFunc (func);
	this.setFinish (finish);
};

Tween.extend (Motion);

var TP = Tween.prototype;


//////// PUBLIC METHODS

TP.toString = function () {
	return "[Tween obj=" + this.obj + " prop=" + this.prop + 
		" beg=" + this.begin + " fin=" + this.finish + " dur=" + this.duration +
		" t=" + this.time + 
		" pos=" + this.getPosition() + "]";
};

TP.continueTo = function (finish, duration) {
    this.setBegin (this.getPosition());
    this.setFinish (finish);
    if (duration != undefined)
        this.setDuration (duration);
    this.start();
};

TP.yoyo = function () {
    with (this) {
        continueTo (getBegin(), getTime());
    }
};


//////// GETTER/SETTER METHODS

TP.getPosition = function (t) {
	if (t == undefined) t = this.$time;
	with (this) return $func (t, $begin, $change, $duration);
};

TP.setFunc = function (f) {
	this.$func = f;
};

TP.getFunc = function () {
	return this.$func;
};

TP.setChange = function (c) {
	this.$change = c;
};

TP.getChange = function () {
	return this.$change;
};

TP.setFinish = function (f) {
	this.$change = f - this.$begin;
};

TP.getFinish = function () {
	return this.$begin + this.$change;
};

/////////// GETTER/SETTER PROPERTIES

with (TP) {
	addProperty ("func", getFunc, setFunc);
	addProperty ("change", getChange, setChange);
	addProperty ("finish", getFinish, setFinish);
}

delete TP;

trace (">> Tween class loaded");