Flash/Flex学习笔记(30)：不用startDrag和stopDrag的对象拖动

对于从Sprite类继承来的对象，要实现拖放当然是Flash/Flex学习笔记(13)：对象拖动(startDrag/stopDrag) 里讲的方法最方便，但是对于不是从Sprite类继承得来的对象，这startDrag/stopDrag是不能用的，这时候只能采用最通常用做法：利用Mouse_Down,Mouse_UP,Mouse_Move事件来处理

注意：对象的Mouse_Move事件，只有当鼠标在对象上时才能被监听，如果用户鼠标移动过快，超出了对象的范围，该事件就不起作用了，所以监听Mouse_Move事件时，应该监听stage对象的Mouse_Move事件，而非对象本身的（详情见下面的代码）

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package {

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import flash.display.Sprite;

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import flash.events.MouseEvent;

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import flash.ui.MouseCursor;

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import flash.ui.Mouse;

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public class MouseMoveDrag extends Sprite {

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private var offsetX:Number;

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private var offsetY:Number;

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private var arrBalls:Array;

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private var _draggedBall:Ball;

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public function MouseMoveDrag():void {

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arrBalls=new Array(7);

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for (var i:uint=0; i<arrBalls.length; i++) {

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arrBalls[i]=new Ball(20+Math.random()*30,Math.random()*0xffffff);

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arrBalls[i].x=stage.stageWidth*Math.random();

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arrBalls[i].y=stage.stageHeight*Math.random();

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arrBalls[i].addEventListener(MouseEvent.MOUSE_DOWN, MouseDownHandler);

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arrBalls[i].addEventListener(MouseEvent.MOUSE_UP, MouseUpHandler);

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arrBalls[i].addEventListener(MouseEvent.MOUSE_OVER,MouseOverHandler);

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arrBalls[i].addEventListener(MouseEvent.MOUSE_OUT,MouseOutHandler);

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addChild(arrBalls[i]);

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}

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}

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function MouseOverHandler(e:MouseEvent):void {

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Mouse.cursor=MouseCursor.BUTTON;

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}

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function MouseOutHandler(e:MouseEvent):void {

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Mouse.cursor=MouseCursor.AUTO;          

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}

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//开始移动

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function MouseDownHandler(e:MouseEvent):void {

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offsetX=e.localX;

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offsetY=e.localY;           

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_draggedBall = e.target as Ball;

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stage.addEventListener(MouseEvent.MOUSE_MOVE, stageMouseMoveHandler);

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}

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//停止拖动

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function MouseUpHandler(e:MouseEvent):void {

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_draggedBall = null;

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//拖动完成后，移除舞台的Mouse_Move监听

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stage.removeEventListener(MouseEvent.MOUSE_MOVE, stageMouseMoveHandler);

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}

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function stageMouseMoveHandler(e:MouseEvent):void {

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//trace(e.target);

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var _ball:Ball=e.target as Ball;

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if (_ball!=null) {

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//设置新的坐标

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_ball.x=mouseX-offsetX;

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_ball.y=mouseY-offsetY;

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}

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else {

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//trace("您拖得太快了!" + _draggedBall.toString());

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if (_draggedBall!=null){

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_draggedBall.x=mouseX-offsetX;

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_draggedBall.y=mouseY-offsetY;

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}

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}

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}

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}

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}