as3 模拟“抛”的动作

1: package     2: {   3:     import flash.display.Sprite;   4:        5:     /**   6:      * ...   7:      * @author ...   8:      */   9:     public class Ball extends Sprite  10:     {  11:         public var radius:Number;  12:         private var color:uint;  13:         public var vx:Number;  14:         public var vy:Number;  15:           16:         public function Ball(radius:Number=40, color:uint=0xff0000)   17:         {  18:             this.radius = radius;  19:             this.color = color;  20:               21:             init();  22:         }  23:           24:         private function init():void {  25:             graphics.clear();  26:             graphics.beginFill(color);  27:             graphics.drawCircle(0, 0, radius);  28:             graphics.endFill();  29:         }  30:           31:     }  32:       33: }

1: package     2: {   3:     import flash.accessibility.Accessibility;   4:     import flash.display.Sprite;   5:     import flash.display.Stage;   6:     import flash.display.StageAlign;   7:     import flash.display.StageScaleMode;   8:     import flash.events.Event;   9:     import flash.events.MouseEvent;  10:     import flash.geom.Rectangle;  11:       12:     /**  13:      * ...  14:      * @author ...  15:      */  16:     public class Throwing extends Sprite  17:     {  18:           19:         private var ball:Ball;  20:         private var vx:Number;  21:         private var vy:Number;  22:         private var bounce:Number = -0.7;  23:         private var gravity:Number = .5;  24:         private var oldX:Number;  25:         private var oldY:Number;  26:           27:         public function Throwing()   28:         {  29:             init();  30:         }  31:           32:         private function init():void {  33:             stage.scaleMode = StageScaleMode.NO_SCALE;  34:             stage.align = StageAlign.TOP_LEFT;  35:               36:             ball = new Ball();  37:             ball.x = stage.stageWidth / 2;  38:             ball.y = stage.stageHeight / 2;  39:             vx = Math.random() * 10 - 5;  40:             vy = -10;  41:               42:             addChild(ball);  43:             ball.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);  44:             addEventListener(Event.ENTER_FRAME, onEnterFrame);  45:         }  46:           47:         private function onMouseDown(evt:MouseEvent):void {  48:             oldX = ball.x;  49:             oldY = ball.y;  50:               51:             stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUp);  52:               53:             ball.startDrag(false, new Rectangle(ball.radius, ball.radius,stage.stageWidth - ball.radius*2, stage.stageHeight - ball.radius*2));  54:               55:             removeEventListener(Event.ENTER_FRAME, onEnterFrame);  56:             addEventListener(Event.ENTER_FRAME, trackVelocity);  57:         }  58:           59:         private function onMouseUp(evt:MouseEvent):void {  60:             stage.removeEventListener(MouseEvent.MOUSE_UP, onMouseUp);  61:             ball.stopDrag();  62:             removeEventListener(Event.ENTER_FRAME, trackVelocity);  63:             addEventListener(Event.ENTER_FRAME, onEnterFrame);  64:         }  65:           66:         private function trackVelocity(evt:Event):void {  67:             vx = ball.x - oldX;  68:             vy = ball.y - oldY;  69:               70:             oldX = ball.x;  71:             oldY = ball.y;  72:         }  73:           74:         private function onEnterFrame(evt:Event):void {  75:             vx += gravity;  76:             ball.x += vx;  77:             ball.y += vy;  78:             var left:Number = 0;  79:             var right:Number = stage.stageWidth;  80:             var top:Number = 0;  81:             var bottom:Number = stage.stageHeight;  82:               83:             if (ball.x + ball.radius > right) {  84:                 ball.x = right - ball.radius;  85:                 vx *= bounce;  86:             } else if (ball.x - ball.radius < left) {  87:                 ball.x = left + ball.radius;  88:                 vx *= bounce;  89:             }  90:               91:             if (ball.y + ball.radius > bottom) {  92:                 ball.y = bottom - ball.radius;  93:                 vy *= bounce;  94:             } else if (ball.y - ball.radius < top) {  95:                 ball.y = top + ball.radius;  96:                 vy *= bounce;  97:             }  98:               99:         } 100:          101:     } 102:      103: }