AS3 碰撞检测

//以下转来的

hitTest () 方法   

public function hitTest(firstPoint:Point, firstAlphaThreshold:uint, secondObject:Object, secondBitmapDataPoint:Point = null, secondAlphaThreshold:uint = 1):Boolean

firstPoint: 表示从哪一点开始进行测试, 一般是new Point(), 即本bitmapdata的 0,0位置. 如果不是0,0(x,y),则表示从x,y之前的区域不参与计算.
firstAlphaThreshold: 表示本bitmapdata参与测试时的alpha最小值,当此值小于BitmapData 构造方法的最后一个参数fillColor值的alpha值时才会测试成功.
secondObject: 要测试目标.

用API中提供的例子来修改:

import flash.display.BitmapData;
import flash.geom.Rectangle;
import flash.geom.Point;

var bmd1:BitmapData = new BitmapData(80, 80, true, 0xfd000000); //设置alpha为0xfd, 即253
var rect:Rectangle = new Rectangle(20, 20, 40, 40);
bmd1.fillRect(rect, 0xFF0000FF);

var pt1:Point = new Point(31, 30);
trace(bmd1.hitTest(pt1, 0xfe, pt1)); //当设置为0xfe时,为false, 只有小于等于0xfd才为true
var pt2:Point = new Point(30, 30); //当设置为30,30时,为false, 因为pt1设置的是(31,30),即当前pt2的位置小于pt1的位置,所以不做测试计算. 所以当设置的位置大于(31,30)才返回true.
trace(bmd1.hitTest(pt1, 0xfd, pt2));

如果通过bitmapdata.draw(...)画出一个带有透明度的IBitmapDrawable对象,则在new Bitmapdata()时, 除了设置第三个参数为true外, 最后一个参数fillColor应该设置为 0x00ffffff.






package
{
	import flash.display.Bitmap;
	import flash.display.BitmapData;
	import flash.display.Sprite;
	import flash.display.StageAlign;
	import flash.display.StageScaleMode;
	import flash.events.Event;
	import flash.events.MouseEvent;
	import flash.filters.GlowFilter;
	import flash.geom.Matrix;
	import flash.geom.Point;

	[SWF(width="760",height="660", backgroundColor="#000000",frameRate="24")]	
	public class only_test extends Sprite
	{

		private var bitMapData1:BitmapData;
		private var bitMap1:Bitmap;
		private var bitMapData2:BitmapData;
		private var bitMap2:Bitmap;
		public function only_test()
		{
			super();
			init();
		}
		private function init():void
		{
			stage.align = StageAlign.TOP_LEFT;
			stage.scaleMode = StageScaleMode.NO_SCALE;
			//当前类加到舞台触发事件
			this.addEventListener(Event.ADDED_TO_STAGE,onAddStage);
			
		}
		private function onAddStage(e:Event):void
		{
			var sp1:Sprite = new Sprite();
			sp1.graphics.beginFill(0x78945612,1);
			sp1.graphics.drawRect(10,10, 50,50);
			sp1.graphics.endFill();
			
			bitMapData1 = new BitmapData(50, 50, false,0x12345678);
			bitMapData1.draw(sp1, new Matrix(1,0,0,1,50,50));
			bitMap1 = new Bitmap(bitMapData1);
			bitMap1.x = 50;
			bitMap1.y = 50;
			
			bitMapData2 = new BitmapData(50, 50, false, 0x45678912);
			bitMapData2.draw(sp1, new Matrix(1,0,0,1,50,50));
			bitMap2 = new Bitmap(bitMapData2);
			addChild(bitMap1);
			addChild(bitMap2);
			
			stage.addEventListener(MouseEvent.CLICK, onClick);
		}
		
		private function onClick(e:MouseEvent):void
		{
			stage.removeEventListener(MouseEvent.CLICK, onClick);
			stage.addEventListener(MouseEvent.MOUSE_MOVE, onMove);
		}
		private function onMove(e:MouseEvent):void
		{
			bitMap2.x = mouseX- 25;
			bitMap2.y = mouseY-25;
			if(bitMapData1.hitTest(new Point(bitMap1.x, bitMap1.y), 255, bitMap2, new Point(bitMap2.x, bitMap2.y)))
			{
				bitMap1.filters = [new GlowFilter()];
				bitMap2.filters = [new GlowFilter()];
			}
			else
			{
				bitMap1.filters = null;
				bitMap2.filters = null;
			}
		}

	}
}