[ActionScript 3.0] 动态绘制扇形实例（拖拽绘制）

package
{
    import flash.display.Shape;
    import flash.display.Sprite;
    import flash.events.MouseEvent;
    
    /**
     * @author Frost.Yen
     * @E-mail 871979853@qq.com
     * @create 2015-7-13 上午11:14:16
     *
     */
    [SWF(width="800",height="600")]
    public class DrawSectorTest extends Sprite
    {
        private var _sector:Sprite;
        private var _dragSp:Sprite;
        private var _radian:Number;//弧度
        private const _radius:uint = 100;//半径
        private const _angle:Number = 60;//初始角度
        public function DrawSectorTest()
        {
            _sector = new Sprite();
            _dragSp = new Sprite();
            _sector.x = _dragSp.x = stage.stageWidth*0.5;
            _sector.y = _dragSp.y = stage.stageHeight*0.5;
            this.addChild(_sector);
            this.addChild(_dragSp);
            
            
            _dragSp.graphics.beginFill(0,.2);
            _dragSp.graphics.drawRect(0,-5,_radius,10);
            _dragSp.graphics.endFill();
            
            drawSector(_sector,0,0,_radius,_angle,0);
            _dragSp.rotation = _angle;
            _dragSp.addEventListener(MouseEvent.MOUSE_DOWN,onDragDown);
        }
        private function onDragDown(e:MouseEvent):void
        {
            stage.addEventListener(MouseEvent.MOUSE_MOVE,onDragMove);
            stage.addEventListener(MouseEvent.MOUSE_UP,onDragOut);
        }
        private function onDragMove(e:MouseEvent):void
        {
            _dragSp.rotation = Math.atan2(_dragSp.parent.mouseY - _dragSp.y,_dragSp.parent.mouseX - _dragSp.x) * 180 / Math.PI ;
            _radian = (_dragSp.rotation) * Math.PI / 180;
            /**这是关键，因为rotation的区间是[0,180][0,-180],如果直接用_dragSp.rotation会导致拖拽绘制扇形错误*/
            if (_dragSp.rotation > 180){
                _radian = _radian + Math.PI;
            }
            if (_radian < 0){
                _radian = _radian + 2 * Math.PI;
            }
            drawSector(_sector,0,0,_radius,_radian*180/Math.PI,0);
        }
        private function onDragOut(e:MouseEvent):void
        {
            stage.removeEventListener(MouseEvent.MOUSE_MOVE,onDragMove);
            stage.removeEventListener(MouseEvent.MOUSE_UP,onDragOut);
            
        }
        /**
         * 绘制扇形
         * @param    mc 承载扇形的对象
         * @param    x 圆心角x
         * @param    y 圆心角y
         * @param    r 半径
         * @param    angle 绘制角度
         * @param    startAngle 起始角度
         * @param    color 填充颜色
         * @param    hasFrame 是否填充边框
         */
        private function drawSector(sp:Sprite,x:Number=0,y:Number=0,r:Number=100,angle:Number=60,startAngle:Number=0,color:Number=0xff0000,hasFrame:Boolean=true):void {
            sp.graphics.clear();
            if(hasFrame) {
                sp.graphics.lineStyle(0,0xffff00);
            }
            sp.graphics.beginFill(color,1);
            sp.graphics.moveTo(x,y);
            angle=(Math.abs(angle)>360)?360:angle;
            var n:Number=Math.ceil(Math.abs(angle)/45);
            var angleA:Number=angle/n;
            angleA=angleA*Math.PI/180;
            startAngle=startAngle*Math.PI/180;
            sp.graphics.lineTo(x+r*Math.cos(startAngle),y+r*Math.sin(startAngle));
            for (var i:int=1; i<=n; i++) {
                startAngle+=angleA;
                var angleMid:Number=startAngle-angleA/2;
                var bx:Number=x+r/Math.cos(angleA/2)*Math.cos(angleMid);
                var by:Number=y+r/Math.cos(angleA/2)*Math.sin(angleMid);
                var cx:Number=x+r*Math.cos(startAngle);
                var cy:Number=y+r*Math.sin(startAngle);
                sp.graphics.curveTo(bx,by,cx,cy);
            }
            if (angle!=360) {
                sp.graphics.lineTo(x,y);
            }
            sp.graphics.endFill();
        }
    }
}