Flash/Flex学习笔记(26)：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）
package {
?import flash.display.Sprite;
?import flash.events.MouseEvent;
?import flash.ui.MouseCursor;
?import flash.ui.Mouse;
?public class MouseMoveDrag extends Sprite {
?private var offsetX:Number;
?private var offsetY:Number;
?private var arrBalls:Array;
?private var _draggedBall:Ball;
public function MouseMoveDrag():void {
?arrBalls=new Array(7);
?for (var i:uint=0; i<arrBalls.length; i++) {
?arrBalls[i]=new Ball(20+Math.random()*30,Math.random()*0xffffff);
?arrBalls[i].x=stage.stageWidth*Math.random();
?arrBalls[i].y=stage.stageHeight*Math.random();
?arrBalls[i].addEventListener(MouseEvent.MOUSE_DOWN, MouseDownHandler);
?arrBalls[i].addEventListener(MouseEvent.MOUSE_UP, MouseUpHandler);
arrBalls[i].addEventListener(MouseEvent.MOUSE_OVER,MouseOverHandler);
?arrBalls[i].addEventListener(MouseEvent.MOUSE_OUT,MouseOutHandler);
addChild(arrBalls[i]);
?}
?}
function MouseOverHandler(e:MouseEvent):void {
?Mouse.cursor=MouseCursor.BUTTON;
?}
?function MouseOutHandler(e:MouseEvent):void {
Mouse.cursor=MouseCursor.AUTO;??????????
?}
?//开始移动 function MouseDownHandler(e:MouseEvent):void {
?offsetX=e.localX;
?offsetY=e.localY;???????????
_draggedBall = e.target as Ball;
stage.addEventListener(MouseEvent.MOUSE_MOVE, stageMouseMoveHandler);
}
?//停止拖动
?function MouseUpHandler(e:MouseEvent):void {
?_draggedBall = null;
//拖动完成后，移除舞台的Mouse_Move监听
?stage.removeEventListener(MouseEvent.MOUSE_MOVE, stageMouseMoveHandler);
?}
function stageMouseMoveHandler(e:MouseEvent):void {
//trace(e.target);
var _ball:Ball=e.target as Ball;
?if (_ball!=null) {
?//设置新的坐标
?_ball.x=mouseX-offsetX;
?_ball.y=mouseY-offsetY;
?} else {
?//trace("您拖得太快了!" + _draggedBall.toString());
?if (_draggedBall!=null){
?_draggedBall.x=mouseX-offsetX;
?_draggedBall.y=mouseY-offsetY;
}
?}
}
}
}
