package

 {

     import flash.display.Shape;

     import flash.display.Sprite;

     import flash.events.MouseEvent;

     import flash.geom.Point;

     import flash.text.TextField;

     /**

      * @author Frost.Yen

      * @E-mail 871979853@qq.com

      * @create 2015-8-18 下午3:16:57

      *

      */

     [SWF(width="1024",height="768")]

     public class DrawTriangle extends Sprite

     {

         private var _pointArr:Array = [new Point(200,150),new Point(500,300),new Point(150,400)];

         private var _btn:TextField;

         private var _container:Sprite;

         private var _heightShape:Shape;

         private var _pointA:TextField;

         private var _pointB:TextField;

         private var _pointC:TextField;

         private var _pointD:TextField;

         public function DrawTriangle()

         {

             initViews();

             initEventListeners();

         }

         private function initViews():void

         {

             _container = new Sprite();

             _btn = new TextField();

             _heightShape = new Shape();

             _btn.selectable = false;

             _btn.border = true;

             _btn.htmlText = "点击随机生成三角形";

             _btn.autoSize = "left";

             _btn.background = true;

             _btn.backgroundColor = 0xdddddd;

             _btn.x = 100;

             _btn.y = 100;

             _pointA = getText(_container);

             _pointB = getText(_container);

             _pointC = getText(_container);

             _pointD = getText(_container);

             this.addChild(_btn);

             this.addChild(_container);

             this.addChild(_heightShape);

         }

         private function initEventListeners():void

         {

             _btn.addEventListener(MouseEvent.CLICK,onCreatClick);

             _pointA.addEventListener(MouseEvent.CLICK,onGetHeight);

             _pointB.addEventListener(MouseEvent.CLICK,onGetHeight);

             _pointC.addEventListener(MouseEvent.CLICK,onGetHeight);

         }

         private function onCreatClick(e:MouseEvent):void

         {

             creatTriangle();

         }

         private function creatTriangle():void

         {

             getPoint();

             _pointArr.sortOn("y");

             _heightShape.graphics.clear();

             _container.graphics.clear();

             _container.graphics.lineStyle(2,0xff0000);

             _container.graphics.moveTo(_pointArr[0].x,_pointArr[0].y);

             _container.graphics.lineTo(_pointArr[1].x,_pointArr[1].y);

             _container.graphics.moveTo(_pointArr[1].x,_pointArr[1].y);

             _container.graphics.lineTo(_pointArr[2].x,_pointArr[2].y);

             _container.graphics.moveTo(_pointArr[2].x,_pointArr[2].y);

             _container.graphics.lineTo(_pointArr[0].x,_pointArr[0].y);

             setText(_pointD,"");

             setText(_pointA,"A("+_pointArr[0].x+","+_pointArr[0].y+")",_pointArr[0].x,_pointArr[0].y);

             setText(_pointB,"B("+_pointArr[1].x+","+_pointArr[1].y+")",_pointArr[1].x,_pointArr[1].y);

             setText(_pointC,"C("+_pointArr[2].x+","+_pointArr[2].y+")",_pointArr[2].x,_pointArr[2].y);

         }

         private function onGetHeight(e:MouseEvent):void

         {

             var point:Point;

             var start:Point;

             switch(e.currentTarget){

                 case _pointA:

                     point = getCrossoverByVertex(_pointArr[0],_pointArr[1],_pointArr[2]);

                     break;

                 case _pointB:

                     point = getCrossoverByVertex(_pointArr[1],_pointArr[0],_pointArr[2]);

                     break;

                 case _pointC:

                     point = getCrossoverByVertex(_pointArr[2],_pointArr[0],_pointArr[1]);

                     break;

             }

             setText(_pointD,"C("+point.x+","+point.y+")",point.x,point.y);

         }

         /**

          * 随机生成三个顶点

          */

         private function getPoint():void

         {

             _pointArr = [];

             for(var i:int = 0;i<3;i++){

                 var point:Point = new Point(Math.floor(Math.random()*400)+150,Math.floor(Math.random()*400+150));

                 _pointArr.push(point);

             }

             var k:Number = (_pointArr[2].y-_pointArr[1].y)/(_pointArr[2].x-_pointArr[1].x);

             var b:Number = _pointArr[2].y-k*_pointArr[2].x;

             if(_pointArr[0].y == k*_pointArr[0].x+b ){//判断三个点是否在同一直线

                 trace("三个点处于同一直线");

                 getPoint();

             }

         }

         /**

          * 获取顶点的高线与对边的交点

          * @param    vertex 顶点

          * @param    point1 三角形另外两点之一

          * @param    point2 三角形另外两点之一

          * @return

          */

         private function getCrossoverByVertex(vertex:Point,point1:Point,point2:Point):Point

         {

             if(point2.y == point1.y){

                 return new Point(vertex.x,point1.y);

             }

             var k1:Number;//顶点对角线的斜率（即A点对角线为BC）

             var b1:Number;//顶点对角线的直线方程的常数

             var k2:Number;//高所在直线的斜率

             var b2:Number;//高所在直线方程的常数

             var crossPoint:Point = new Point();//高线和顶点对角线的交点

             k1 = (point2.y - point1.y)/(point2.x - point1.x);

             b1 = point1.y - k1 * point1.x;

             k2 = -1 / k1 ;

             b2 = vertex.y-k2*vertex.x;

             crossPoint.x = (b1 - b2)/(k2 - k1);

             crossPoint.y = k1 * ((b1 - b2)/(k2 - k1)) + b1;

             drawHeight(vertex,crossPoint);

             return crossPoint;

         }

         private function drawHeight(start:Point,end:Point):void

         {

             _heightShape.graphics.clear();

             _heightShape.graphics.lineStyle(2,0xff00ff);

             _heightShape.graphics.moveTo(start.x,start.y);

             _heightShape.graphics.lineTo(end.x,end.y);

             _heightShape.graphics.endFill();

         }

         private function getText(parent:Sprite):TextField

         {

             var t:TextField = new TextField;

             t.autoSize = "left";

             t.selectable = false;

             parent.addChild(t);

             return t;

         }

         private function setText(t:TextField,text:String,x:Number=0,y:Number=0):void

         {

             t.text = text;

             t.x = x;

             t.y = y;

         }

     }

 }