1）何时停止缓动：
private function onEnterFrame(event : Event) : void {
var dx:Number = targetX - ball.x;
if (Math.abs(dx) < 1){
ball.x = targetX;
removeEventListener(Event.ENTER_FRAME,onEnterFrame);
} else {
var vx:Number = dx * easing;
ball.x += vx;
}
}
}
2) 重影效果可以让第一个影子缓动至物体，第二个影子缓动至第一个影子，第三个影子缓动至第二个影子。。。
function onEnterFrame(event:Event): void{
moveBall(ball0,mouseX,mouseY);
moveBall(ball1,ball0.x,ball0.y);
moveBall(ball2,ball1.x,ball1.y);
}
private function moveBall(ball:Ball,targetX:Number,targetY:Number):void{
ball.vx += (targetX - ball.x) * spring;
ball.vy += (targetY - ball.y) * spring;
ball.vy += gravity;
ball.vx *= friction;
ball.vy *= friction;
ball.x += ball.vx;
ball.y += ball.vy;
}
3) 缓动：
ball.x += (targetX - ball.x) * 0.2;
ball.y += (targetY - ball.y) * 0.2;
4) 弹性：
dx = targetX - ball.x;
dy = targetY - ball.y;
ax = dx * 0.2;
ay = dx * 0.2;
vx += ax;
vy += ay;
vx *= friction;
vy *= friction;
ball.x += vx;
ball.y += vy;