以一个小球为示例，在鼠标点击的时修改它的加速度值(在短时间内移动的距离)，加速度以一个值加速，在遇到边界时进行反向。
代码参考自：《ActionScript 3.0 动画教程》，添加了拖动时的范围限定<在整个文档内进行拖动>。
Ball.as
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: }
Throwing.as
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: }
