Flash/Flex学习笔记(13)：对象拖动(startDrag/stopDrag)
Flash中只有影片MovieClip(准确的讲是Sprite)可以调用startDrag,endDrag，创建对象拖动最简单的办法只要调用这二个方法即可
01 myobj.addEventListener(MouseEvent.MOUSE_DOWN,pickup);
02 myobj.addEventListener(MouseEvent.MOUSE_UP,place);
03
04 function pickup(e:MouseEvent ):void {
05 //trace("鼠标按下");
06 e.target.startDrag();
07 }
08
09 function place(e:MouseEvent):void {
10 //trace("鼠标抬起");
11 e.target.stopDrag();
12 }
其中myobj是舞台上的随便一个MovieClip实例
startDarg还能在拖动时，设定拖动的边界：
01 var ball:Ball=new Ball(30,Math.random()*0xffffff);
02
03 var posX:Number = stage.stageWidth /2;
04 var posY:Number = stage.stageHeight/2;
05 var rectSize:Number = 200;
06
07 ball.x = posX;
08 ball.y = posY;
09
10 addChild(ball);
11
12 ball.addEventListener(MouseEvent.MOUSE_OVER,function(){Mouse.cursor = MouseCursor.HAND });
13 ball.addEventListener(MouseEvent.MOUSE_OUT,function(){Mouse.cursor = MouseCursor.AUTO });
14 ball.addEventListener(MouseEvent.MOUSE_DOWN,MouseDownHandler);
15
16 function MouseDownHandler(e:MouseEvent) {
17 stage.addEventListener(MouseEvent.MOUSE_UP, MouseUpHandler);
18 //第一参数如果为true,则表示拖动时，鼠标所在点自动对齐对象中心--即所谓的锁定中心
19 ball.startDrag(true,new Rectangle(posX-rectSize/2, posY-rectSize/2, rectSize, rectSize));
20 //画出边界，方便更直观显示
21 graphics.clear();
22 graphics.lineStyle(1);
23 graphics.drawRect(posX-rectSize/2, posY-rectSize/2, rectSize, rectSize);
24 }
25
26 function MouseUpHandler(e:MouseEvent) {
27 ball.stopDrag();
28 }
下面再来一个稍复杂一点的示例：
01 R1.addEventListener(MouseEvent.MOUSE_DOWN,MouseDownHandler);
02 R1.addEventListener(MouseEvent.MOUSE_UP,MouseUpHandler);
03 R2.addEventListener(MouseEvent.MOUSE_DOWN,MouseDownHandler);
04 R2.addEventListener(MouseEvent.MOUSE_UP,MouseUpHandler);
05 R3.addEventListener(MouseEvent.MOUSE_DOWN,MouseDownHandler);
06 R3.addEventListener(MouseEvent.MOUSE_UP,MouseUpHandler);
07
08 //trace(numChildren);//当前舞台上的元素总数
09
10 var _originPoint:Point = new Point();
11
12 //拖动开始时
13 function MouseDownHandler(e:MouseEvent) {
14 //trace(e);
15
16 //保存原始位置(拖动完成时恢复用)
17 _originPoint.x=e.target.x;
18 _originPoint.y=e.target.y;
19
20 e.target.startDrag();
21
22 setChildIndex(DisplayObject(e.target), numChildren-1);//设置拖动对象的zIndex，否则有可能在拖动过程中被其它组件挡住
23
24 //拖动时显示阴影
25 var _shadow:DropShadowFilter = new DropShadowFilter();
26 _shadow.distance=10;
27 _shadow.alpha=0.5;
28 _shadow.color = 0xFFFFFF;
29 e.target.filters=[_shadow];
30
31 Mouse.cursor = MouseCursor.HAND;
32
33 }
34
35 //拖动完成时
36 function MouseUpHandler(e:MouseEvent) {
37 e.target.stopDrag();
38 e.target.filters=null;
39
40 if (e.target.dropTarget is Shape){
41 e.target.dropTarget.transform.colorTransform=e.target.transform.colorTransform; //将目标对象颜色设置为与源对象一致
42 }
43 //还原初始位置
44 e.target.x = _originPoint.x;
45 e.target.y = _originPoint.y;
46
47 Mouse.cursor = MouseCursor.ARROW;
48 }
源文件下载：http://cid-2959920b8267aaca.skydrive.live.com/self.aspx/Flash/DragObject.rar
