import Motion;
class Tween extends Motion {
  var func:Function;//变形函数
  var finish:Number;//运动开始位置
  var begin:Number;//动动结束位置
  var change:Number;//位置的改变
  var duration:Number;//运动持续的时间
/********************************************/
  function setFunc(f:Function):Void{
    this.func=f;
  }
  function getFunc():Function{
    return this.func;
  }
  function setFinish(f:Number):Void{
    this.change = f - this.begin;
  }
  /*因为变形函数是以位置的改变为参数的，所以setFinish方法是用来获得change值的*/
  function getFinish():Number{
    return this.begin + this.change;
  }
    function setChange(c:Number):Void{
    this.change = c;
  }
  function getChange():Number{
    return this.change;
  }
  function getPosition(t:Number):Number{
    if (t == undefined) t = this.time;
     return func(t,begin,change,duration);
  }
/********************************************/
  function toString():String{
    return "[Tween obj=" + this.obj + " prop=" + this.prop +
    " beg=" + this.begin + " fin=" + this.finish + " dur=" + this.duration +
    " t=" + this.time +
    " pos=" + this.getPosition() + "]";
}
  function continueTo(finish:Number,duration:Number):Void{
    this.setBegin (this.getPosition());
this.setFinish (finish);
if (duration != undefined)
this.setDuration (duration);
this.start();
  }
  function yoyo():Void{
    with (this) {
continueTo (getBegin(), getTime());
}
}
/********************************************/
  function Tween(  obj:MovieClip,prop:String,func:Function,begin:Number,finish:Number,duration:Number, useSeconds:Boolean){
    super(obj, prop, begin, duration, useSeconds);
    this.setFunc (func);
    this.setFinish (finish);
    
  }
  }