阅读本文，你可以了解 AS3中判断线段和矩形是否相交的一种方法。 实例如下： RectLine
源码如下：（判断方法来自网上，原方法是java的） [codesyntax lang=”php”]
package
{
import flash.display.Sprite;
import flash.events.MouseEvent;
import flash.text.TextField;
[SWF(width=375,height=300,backgroundColor=”0xeeeeee”)]
public class RectLine extends Sprite
{
private var txt:TextField;
public function RectLine()
{
this.txt = new TextField();
addChild(txt);
stage.addEventListener(MouseEvent.CLICK,ckHandler);
ckHandler(null);
}
private function ckHandler(e:MouseEvent):void
{
graphics.clear();
graphics.beginFill(0x00ffff);
graphics.drawRect(100,100,200,50);
graphics.endFill();
var a:int = Math.random()*375;
var b:int = Math.random()*300;
var c:int = Math.random()*375;
var d:int = Math.random()*300;
graphics.lineStyle(2,0xff0000);
graphics.moveTo(a,b);
graphics.lineTo(c,d);
trace(isLineIntersectRectangle(a,b,c,d,100,100,300,150));
var isF:Boolean = isLineIntersectRectangle(a,b,c,d,100,100,300,150);
txt.text = “是否相交：”+isF;
}
/**
判断线段是否在矩形内
* 先看线段所在直线是否与矩形相交，
* 如果不相交则返回false，
* 如果相交，
* 则看线段的两个点是否在矩形的同一边（即两点的x(y)坐标都比矩形的小x(y)坐标小，或者大）,
* 若在同一边则返回false，
* 否则就是相交的情况。
* @param linePointX1 线段起始点x坐标
* @param linePointY1 线段起始点y坐标
* @param linePointX2 线段结束点x坐标
* @param linePointY2 线段结束点y坐标
* @param rectangleLeftTopX 矩形左上点x坐标
* @param rectangleLeftTopY 矩形左上点y坐标
* @param rectangleRightBottomX 矩形右下点x坐标
* @param rectangleRightBottomY 矩形右下点y坐标
* @return 是否相交
*/
private function isLineIntersectRectangle(linePointX1:Number,
linePointY1:Number,
linePointX2:Number,
linePointY2:Number,
rectangleLeftTopX:Number,
rectangleLeftTopY:Number,
rectangleRightBottomX:Number,
rectangleRightBottomY:Number):Boolean
{
var lineHeight:Number = linePointY1 - linePointY2;
var lineWidth:Number = linePointX2 - linePointX1; // 计算叉乘
var c:Number = linePointX1 * linePointY2 - linePointX2 * linePointY1;
if ((lineHeight * rectangleLeftTopX + lineWidth * rectangleLeftTopY + c >= 0 && lineHeight * rectangleRightBottomX + lineWidth * rectangleRightBottomY + c <= 0)
(lineHeight * rectangleLeftTopX + lineWidth * rectangleLeftTopY + c <= 0 && lineHeight * rectangleRightBottomX + lineWidth * rectangleRightBottomY + c >= 0)
(lineHeight * rectangleLeftTopX + lineWidth * rectangleRightBottomY + c >= 0 && lineHeight * rectangleRightBottomX + lineWidth * rectangleLeftTopY + c <= 0)
(lineHeight * rectangleLeftTopX + lineWidth * rectangleRightBottomY + c <= 0 && lineHeight * rectangleRightBottomX + lineWidth * rectangleLeftTopY + c >= 0))
{
if (rectangleLeftTopX > rectangleRightBottomX) {
var temp:Number = rectangleLeftTopX;
rectangleLeftTopX = rectangleRightBottomX;
rectangleRightBottomX = temp;
}
if (rectangleLeftTopY < rectangleRightBottomY) {
var temp1:Number = rectangleLeftTopY;
rectangleLeftTopY = rectangleRightBottomY;
rectangleRightBottomY = temp1; }
if ((linePointX1 < rectangleLeftTopX && linePointX2 < rectangleLeftTopX)
(linePointX1 > rectangleRightBottomX && linePointX2 > rectangleRightBottomX)
(linePointY1 > rectangleLeftTopY && linePointY2 > rectangleLeftTopY)
(linePointY1 < rectangleRightBottomY && linePointY2 < rectangleRightBottomY)) {
return false;
} else {
return true;
}
} else {
return false;
}
}
}
}
[/codesyntax] 延伸思考：1.旋转后的矩形 是否还能用这个方法进行判断？ 2.直线与其他形状（如椭圆）如何判断相交？ 延伸阅读：公式汇总 http://blog.sqstudio.com/formula