检测碰撞实例

一个基于as3的碰撞检测类：

三个参数（第一个对象:DisplayObject、

第二个对象:DisplayObject、精度:Number），

返回一个布尔值

package
{

	import flash.display.BitmapData;
	import flash.display.BlendMode;
	import flash.display.DisplayObject;
	import flash.display.Sprite;

	import flash.geom.ColorTransform;
	import flash.geom.Matrix;
	import flash.geom.Point;
	import flash.geom.Rectangle;

	public class HitTest
	{
		public static function complexHitTestObject( target1:DisplayObject, target2:DisplayObject,  accuracy:Number = 1 ):Boolean
		{
			return complexIntersectionRectangle( target1, target2, accuracy ).width != 0;
		}

		public static function intersectionRectangle( target1:DisplayObject, target2:DisplayObject ):Rectangle
		{
			// If either of the items don't have a reference to stage, then they are not in a display list
			// or if a simple hitTestObject is false, they cannot be intersecting.
			if (! target1.root || ! target2.root || ! target1.hitTestObject(target2))
			{
				return new Rectangle();
			}

			// Get the bounds of each DisplayObject.
			var bounds1:Rectangle = target1.getBounds(target1.root);
			var bounds2:Rectangle = target2.getBounds(target2.root);

			// Determine test area boundaries.
			var intersection:Rectangle = new Rectangle();
			intersection.x = Math.max(bounds1.x,bounds2.x);
			intersection.width     = Math.min( ( bounds1.x + bounds1.width ) - intersection.x, ( bounds2.x + bounds2.width ) - intersection.x );
			intersection.height = Math.min( ( bounds1.y + bounds1.height ) - intersection.y, ( bounds2.y + bounds2.height ) - intersection.y );

			return intersection;
		}

		public static function complexIntersectionRectangle( target1:DisplayObject, target2:DisplayObject, accuracy:Number = 1 ):Rectangle
		{
			if (accuracy <= 0)
			{
				throw new Error("ArgumentError: Error #5001: Invalid value for accuracy",5001);
			}

			// If a simple hitTestObject is false, they cannot be intersecting.
			if (! target1.hitTestObject(target2))
			{
				return new Rectangle();
			}

			var hitRectangle:Rectangle = intersectionRectangle(target1,target2);
			// If their boundaries are no interesecting, they cannot be intersecting.
			if (hitRectangle.width * accuracy < 1 || hitRectangle.height * accuracy < 1)
			{
				return new Rectangle();
			}

			var bitmapData:BitmapData = new BitmapData(hitRectangle.width * accuracy,hitRectangle.height * accuracy,false,0x000000);

			// Draw the first target.
			bitmapData.draw( target1, HitTest.getDrawMatrix( target1, hitRectangle, accuracy ), new ColorTransform( 1, 1, 1, 1, 255, -255, -255, 255 ) );
			// Overlay the second target.
			bitmapData.draw( target2, HitTest.getDrawMatrix( target2, hitRectangle, accuracy ), new ColorTransform( 1, 1, 1, 1, 255, 255, 255, 255 ), BlendMode.DIFFERENCE );

			// Find the intersection.
			var intersection:Rectangle = bitmapData.getColorBoundsRect(0xFFFFFFFF,0xFF00FFFF);

			bitmapData.dispose();

			// Alter width and positions to compensate for accuracy
			if (accuracy != 1)
			{
				intersection.x /=  accuracy;
				intersection.y /=  accuracy;
				intersection.width /=  accuracy;
				intersection.height /=  accuracy;
			}

			intersection.x +=  hitRectangle.x;
			intersection.y +=  hitRectangle.y;

			return intersection;
		}


		protected static function getDrawMatrix( target:DisplayObject, hitRectangle:Rectangle, accuracy:Number ):Matrix
		{
			var localToGlobal:Point;;
			var matrix:Matrix;

			var rootConcatenatedMatrix:Matrix = target.root.transform.concatenatedMatrix;

			localToGlobal = target.localToGlobal( new Point( ) );
			matrix = target.transform.concatenatedMatrix;
			matrix.tx = localToGlobal.x - hitRectangle.x;
			matrix.ty = localToGlobal.y - hitRectangle.y;

			matrix.a = matrix.a / rootConcatenatedMatrix.a;
			matrix.d = matrix.d / rootConcatenatedMatrix.d;
			if (accuracy != 1)
			{
				matrix.scale( accuracy, accuracy );
			}

			return matrix;
		}

	}

}

package 
{

	import flash.display.Sprite;
	import flash.events.MouseEvent;
	import flash.geom.Rectangle;

	public class ComplexIntersectionRectangle extends Sprite
	{

		private var _circle0:Sprite;
		private var _circle1:Sprite;
		private var _hit:Boolean;
		private var _intersection:Sprite;

		public function ComplexIntersectionRectangle()
		{
			super();

			initialize();
		}

		private function initialize():void
		{

			_circle0 = new Sprite();
			_circle0.x = 50;
			_circle0.y = 100;
			_circle0.addEventListener( MouseEvent.MOUSE_DOWN, onCircleMouseDown );
			draw( _circle0, 0xFFFFFF );
			addChild( _circle0 );

			_circle1 = new Sprite();
			_circle1.x = 250;
			_circle1.y = 100;
			_circle1.addEventListener( MouseEvent.MOUSE_DOWN, onCircleMouseDown );
			draw( _circle1, 0xFFFFFF );
			addChild( _circle1 );

			_intersection = new Sprite();
			addChild( _intersection );

			_hit = false;
			stage.addEventListener( MouseEvent.MOUSE_MOVE, onStageMouseMove );
			stage.addEventListener( MouseEvent.MOUSE_UP, onStageMouseUp );
		}

		private function onCircleMouseDown( event:MouseEvent ):void
		{
			var circle:Sprite = Sprite(event.target);
			circle.startDrag( false );
		}

		private function onStageMouseMove( event:MouseEvent ):void
		{
			var intersection:Rectangle = HitTest.complexIntersectionRectangle(_circle0,_circle1,5);
			var hit:Boolean = ( intersection.width > 0 && intersection.height > 0 );

			_intersection.graphics.clear();
			if (hit)
			{
				_intersection.graphics.beginFill( 0xFF0000, 0.5 );
				_intersection.graphics.drawRect( intersection.x, intersection.y, intersection.width, intersection.height );
				_intersection.graphics.endFill();
			}

			if (hit != _hit)
			{
				_hit = hit;
				var color:Number = ( _hit ) ? 0x00FF00 : 0xFFFFFF;
				draw( _circle0, color );
				draw( _circle1, color );
			}
		}

		private function onStageMouseUp( event:MouseEvent ):void
		{
			_circle0.stopDrag();
			_circle1.stopDrag();
		}

		private function draw( circle:Sprite, color:Number ):void
		{
			circle.graphics.clear();
			circle.graphics.beginFill( color, 1 );
			circle.graphics.drawCircle( 0, 0, 25 );
			circle.graphics.endFill();
		}
	}
}