package{
	import Box2D.Collision.Shapes.b2PolygonShape;
	import Box2D.Common.Math.b2Vec2;
	import Box2D.Dynamics.Contacts.b2Contact;
	import Box2D.Dynamics.b2Body;
	import Box2D.Dynamics.b2BodyDef;
	import Box2D.Dynamics.b2DebugDraw;
	import Box2D.Dynamics.b2FixtureDef;
	import Box2D.Dynamics.b2World;
	
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.TimerEvent;
	import flash.utils.Timer;
	
	[SWF(width="800",height="600",frameRate="32",backgroundColor="0x000000")]
	public class Sensor extends Sprite{
		private var world:b2World;
		private var timeStep:Number;
		private var iterations:uint;
		private var pixelsPerMeter:Number = 30;
		private var i:int = 0;
		
		public function Sensor(){
			createWorld();
			makeDebugDraw();
			createGround();
			addEventListener(Event.ENTER_FRAME,onEnterframe);
			var timer:Timer = new Timer(1000);
			timer.addEventListener(TimerEvent.TIMER,onTimer);
			timer.start();
		}
		
		private function createWorld():void{
			var gravity:b2Vec2 = new b2Vec2(0.0,9.8);
			var doSleep:Boolean = true;
			world = new b2World(gravity,doSleep);
			world.SetWarmStarting(true);
			timeStep = 1.0/30.0;
			iterations = 10;
		}
		
		private function makeDebugDraw():void{
			var debugDraw:b2DebugDraw = new b2DebugDraw();
			var debugSprite:Sprite = new Sprite();
			addChild(debugSprite);
			debugDraw.SetSprite(debugSprite);
			debugDraw.SetDrawScale(30.0);
			debugDraw.SetFillAlpha(0.5);
			debugDraw.SetLineThickness(1.0);
			debugDraw.SetFlags(b2DebugDraw.e_shapeBit);
			world.SetDebugDraw(debugDraw);
		}
		
		private function createGround():void{
			var bodyDef:b2BodyDef = new b2BodyDef();
			bodyDef.position.Set(400/pixelsPerMeter,330/pixelsPerMeter);
			var box:b2PolygonShape = new b2PolygonShape();
			box.SetAsBox(400/pixelsPerMeter,15/pixelsPerMeter);
			var fixtureDef:b2FixtureDef = new b2FixtureDef();
			fixtureDef.shape = box;
			fixtureDef.density = 0;
			fixtureDef.friction = 0.3;
			fixtureDef.isSensor = true;
			fixtureDef.userData = "through";
			var body:b2Body = world.CreateBody(bodyDef);
			body.CreateFixture(fixtureDef);
			
			bodyDef.position.Set(400/pixelsPerMeter,585/pixelsPerMeter);
			box.SetAsBox(400/pixelsPerMeter,15/pixelsPerMeter);
			fixtureDef = new b2FixtureDef();
			fixtureDef.shape = box;
			fixtureDef.density = 0;
			fixtureDef.friction = 0.3;
			fixtureDef.isSensor = false;
			fixtureDef.userData = "ground";
			body = world.CreateBody(bodyDef);
			body.CreateFixture(fixtureDef);
		}
		
		private function onTimer(e:TimerEvent = null):void{
			var bodyDef:b2BodyDef = new b2BodyDef();
			bodyDef.type = b2Body.b2_dynamicBody;
			bodyDef.position.Set((Math.random()*300+60)/pixelsPerMeter,0);
			bodyDef.userData = i;
			var box:b2PolygonShape = new b2PolygonShape();
			box.SetAsBox((Math.random()*30+3)/pixelsPerMeter,(Math.random()*30+3)/pixelsPerMeter);
			var fixtureDef:b2FixtureDef = new b2FixtureDef();
			fixtureDef.shape = box;
			fixtureDef.density = 1.0;
			fixtureDef.friction = 0.5;
			fixtureDef.restitution = 0.2;
			var body:b2Body = world.CreateBody(bodyDef);
			body.CreateFixture(fixtureDef);
			i++;
		}
		
		private function onEnterframe(e:Event):void{
			world.Step(timeStep,iterations,iterations);
			world.ClearForces();
			world.DrawDebugData();
			if(world.GetContactList()){
				var contact:b2Contact = world.GetContactList();
				if(contact.GetFixtureA().GetBody().GetUserData() == "ground"){
					trace(contact.GetFixtureB().GetBody().GetUserData());
				}
				if(contact.GetFixtureA().GetBody().GetUserData() == "through"){
					var body:b2Body = contact.GetFixtureB().GetBody();
					world.DestroyBody(body);
				}
			}
		}
	}
}

转载请注明：陈童的博客 » box2d之Sensor传感器