跳ね返り

[sourcecode language=”java”]
package
{
import flash.display.Sprite;
import flash.display.StageAlign;
import flash.display.StageScaleMode;
import flash.events.Event;
import flash.events.MouseEvent;

public class Throwing extends Sprite
{
private var ball:Ball;
private var vx:Number;
private var vy:Number;
private var bounce:Number = -0.7;
private var gravity:Number = .5;
private var oldX:Number;
private var oldY:Number;

public function Throwing()
{
init();
}

private function init():void
{
stage.scaleMode = StageScaleMode.NO_SCALE;
stage.align=StageAlign.TOP_LEFT;

ball = new Ball();
ball.x = stage.stageWidth / 2;
ball.y = stage.stageHeight / 2;
vx = Math.random() * 10 – 5;
vy = -10;
addChild(ball);
ball.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
addEventListener(Event.ENTER_FRAME, onEnterFrame);
}

private function onEnterFrame(event:Event):void
{
vy += gravity;
ball.x += vx;
ball.y += vy;
var left:Number = 0;
var right:Number = stage.stageWidth;
var top:Number = 0;
var bottom:Number = stage.stageHeight;

if(ball.x + ball.radius > right)
{
ball.x = right – ball.radius;
vx *= bounce;
}
else if(ball.x – ball.radius < left)
{
ball.x = left + ball.radius;
vx *= bounce;
}
if(ball.y + ball.radius > bottom)
{
ball.y = bottom – ball.radius;
vy *= bounce;
}
else if(ball.y – ball.radius < top)
{
ball.y = top + ball.radius;
vy *= bounce;
}
}

private function onMouseDown(event:MouseEvent):void
{
oldX = ball.x;
oldY = ball.y;
stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUp);
ball.startDrag();
removeEventListener(Event.ENTER_FRAME, onEnterFrame);
addEventListener(Event.ENTER_FRAME, trackVelocity);
}

private function onMouseUp(event:MouseEvent):void
{
stage.removeEventListener(MouseEvent.MOUSE_UP, onMouseUp);
ball.stopDrag();
removeEventListener(Event.ENTER_FRAME, trackVelocity);
addEventListener(Event.ENTER_FRAME, onEnterFrame);
}

private function trackVelocity(event:Event):void
{
vx = ball.x – oldX;
vy = ball.y – oldY;
oldX = ball.x;
oldY = ball.y;
}
}
}

[/sourcecode]

ボールが跳ね返る