[ActionScript 3.0] AS3 彈性運動

 1 package com.views
 2 {
 3     import flash.display.Sprite;
 4     import flash.events.Event;
 5     import flash.geom.Point;
 6     
 7     /**
 8      * @author Frost.Yen
 9      * @E-mail 871979853@qq.com
10      * @create 2015-8-20 上午11:16:11
11      *
12      */
13     [SWF(width="800",height="600")]
14     public class ElasticMove extends Sprite
15     {
16         private const SPRING:Number=0.1;//彈性係數 
17         private const FRICTION:Number=0.9;//摩擦係數 
18         private const FEAR_DISTANCE:Number=150;//安全距離(小於該距離則發生躲避行爲) 
19         private const MAX_AVOID_FORCE:uint=10;//最大躲避速度 
20         private var _destinationPoint:Point;//目標靜止點(鼠標遠離該物體時，物體最終會靜止的座標點) 
21         private var _speed:Point=new Point(0,0);//速度矢量(_speed.x即至關於vx,_speed.y即至關於vy) 
22         public function ElasticMove()
23         {
24             super();
25             drawStuff(); 
26             destinationPoint = new Point(300,300);
27         }
28         private function drawStuff():void { 
29             //默認先畫一個半徑爲10的圓 
30             graphics.beginFill(Math.random() * 0xFFFFFF); 
31             //graphics.beginFill(0xFFFFFF); 
32             graphics.drawCircle(0, 0, 5); 
33             graphics.endFill(); 
34         }
35         //只寫屬性(設置目標點) 
36         public function set destinationPoint(value:Point):void { 
37             _destinationPoint=value; 
38             addEventListener(Event.ENTER_FRAME, enterFrameHandler); 
39         }
40         protected function enterFrameHandler(e:Event):void { 
41             moveToDestination();//先移動到目標點 
42             avoidMouse();//躲避鼠標 
43             applyFriction();//應用摩擦力 
44             updatePosition();//更新位置 
45         }
46         //以彈性運動方式移動到目標點 
47         private function moveToDestination():void { 
48             _speed.x += (_destinationPoint.x - x) * SPRING; 
49             _speed.y += (_destinationPoint.y - y) * SPRING; 
50         }
51         //躲避鼠標 
52         private function avoidMouse():void { 
53             var currentPosition:Point=new Point(x,y);//肯定當前位置 
54             var mousePosition:Point=new Point(stage.mouseX,stage.mouseY);//確實鼠標位置 
55             var distance:uint=Point.distance(currentPosition,mousePosition);//計算鼠標與當前位置的距離 
56             //若是低於安全距離 
57             if (distance<FEAR_DISTANCE) { 
58                 var force:Number = (1 - distance / FEAR_DISTANCE) * MAX_AVOID_FORCE;//計算(每單位時間的)躲避距離--即躲避速率 
59                 var gamma:Number=Math.atan2(currentPosition.y- mousePosition.y,currentPosition.x- mousePosition.x);//計算鼠標所在位置與當前位置所成的夾角 
60                 var avoidVector:Point=Point.polar(force,gamma);//將極座標轉換爲普通(笛卡爾)座標--其實至關於vx = force*Math.cos(gamma),vy = force*Math.sin(gamma) 
61                 //加速 躲避逃開 
62                 _speed.x+=avoidVector.x; 
63                 _speed.y+=avoidVector.y; 
64             }
65         }
66         //應用摩擦力 
67         private function applyFriction():void { 
68             _speed.x*=FRICTION; 
69             _speed.y*=FRICTION; 
70         }
71         //最終更新自身的位置 
72         private function updatePosition():void { 
73             x+=_speed.x; 
74             y+=_speed.y; 
75         }
76     }
77 }