鼠标控制，扇形的大小

效果如下图：

package
{
	import flash.display.Sprite;
	import flash.events.MouseEvent;
	
	/**
	 *  @author chb
	 *  @Email 645338868@qq.com
	 *  @data 2015-8-28
	 *
	 **/
	[SWF(width="724",height="513",frameRate="60",backgroundColor="0x00cfff")]
	public class DrawSector extends Sprite
	{
		private var sectorSp:Sprite;
		private var dragLineSp:Sprite;
		private var radius:Number;//半径长
		private var initRotation:Number;//初始角度
		
		private var currentRotation:Number;
		
		public function DrawSector()
		{
			init();
		}
		
		private function init():void
		{
			
			sectorSp = new Sprite();
			this.addChild(sectorSp);
			dragLineSp = new Sprite();
			this.addChild(dragLineSp);
			
			sectorSp.x = dragLineSp.x = stage.stageWidth*0.5;
			sectorSp.y = dragLineSp.y = stage.stageHeight*0.5;
			
			radius = 200;
			initRotation = 60;
			
			dragLineSp.graphics.lineStyle(2,0xffff00,1);
			dragLineSp.graphics.moveTo(radius,0);
			dragLineSp.graphics.lineTo(0,0);
			
			dragLineSp.graphics.beginFill(0xffff00,1);
			dragLineSp.graphics.drawCircle(radius,0,5);
			dragLineSp.graphics.endFill();
			
			dragLineSp.rotation = initRotation;
			drawSectorFun(sectorSp,0,0,radius,initRotation,0,0x990000,true);
			dragLineSp.addEventListener(MouseEvent.MOUSE_DOWN,onDragStart);
			
		}
		
		private function onDragStart(e:MouseEvent):void
		{
			stage.addEventListener(MouseEvent.MOUSE_MOVE,onDragMove);
			stage.addEventListener(MouseEvent.MOUSE_UP,onDragStop);
		}
		
		private function onDragMove(e:MouseEvent):void
		{
			dragLineSp.rotation = Math.atan2(dragLineSp.parent.mouseY - dragLineSp.y,dragLineSp.parent.mouseX - dragLineSp.x) * 180 / Math.PI ;//直线随着鼠标旋转
			currentRotation = dragLineSp.rotation;
			/**这是关键，因为rotation的区间是[0,180][0,-180],如果直接用dragLineSp.rotation会导致拖拽绘制扇形错误*/
			if(dragLineSp.rotation < 0)
			{
				currentRotation = dragLineSp.rotation + 360;
			}
			trace(currentRotation);
			drawSectorFun(sectorSp,0,0,radius,currentRotation,0,0x990000,true);
			
		}
		private function onDragStop(e:MouseEvent):void
		{
			stage.removeEventListener(MouseEvent.MOUSE_MOVE,onDragMove);
			stage.removeEventListener(MouseEvent.MOUSE_UP,onDragStop);
		}
		
		/**
		 * 画扇形
		 * @param  mc        扇形的容器
		 * @param  x         扇形的 x 坐标
		 * @param  y         扇形的 y 坐标
		 * @param  r         扇形的 半径
		 * @param  angle     扇形的 角度
		 * @param  startFrom 扇形的初始位置，即从什么位子开始画
		 * @param  color     扇形填充色
		 * @param  hasLine   是否描边
		 * 
		 */
		
		private function drawSectorFun(mc:Sprite, x:Number = 200, y:Number = 200, r:Number = 100, angle:Number = 27, startFrom:Number = 270, color:Number = 0xff00ff, hasLine:Boolean = false):void
		{
			mc.graphics.clear();
			mc.graphics.beginFill(color, 1);
			if(hasLine)
			{
				mc.graphics.lineStyle(2,0x0000ff);
			}
			mc.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;
			startFrom = startFrom * Math.PI / 180;
			mc.graphics.lineTo(x + r * Math.cos(startFrom), y + r * Math.sin(startFrom));
			for (var i:Number = 1; i <= n; i++)
			{
				startFrom +=  angleA;
				var angleMid:Number = startFrom - 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(startFrom);
				var cy:Number = y + r * Math.sin(startFrom);
				mc.graphics.curveTo(bx, by, cx, cy);
			}
			if (angle != 360)
			{
				mc.graphics.lineTo(x, y);
			}
			mc.graphics.endFill();
		}
	}
}