cocos2d for iPhone

A fast, easy to use, free, and community supported 2D game engine

1. 

   phoenixreanimation
   Member

   I took two day,but I still can not fix the problem.
   Thanks for your help.

   I am using the newest box2d template（version 0.8.2 ）.
   When I run the app,it works fine but get 10 warnings:

   warnings:statement has no effect

   And when I added MyContactListener,I get more warnings,and nothing happen.
   I try to printf "Hello World ".
   I add this to HelloWorldScene.m:

   mContactListener = new MyContactListener;
   world->SetContactListener(mContactListener);

   This is MyContactListener class
   

   #include "Box2D.h"
   
   class MyContactListener : public b2ContactListener
   {
   public:
   
   	//Methods override from b2ContactListener
   	void Add(const b2ContactPoint* point) ;
   	void Persist(const b2ContactPoint* point);
   	void Remove(const b2ContactPoint* point);
   
   	//clear contact point vector
   	void Clear();
   
   };

   void MyContactListener::Add(const b2ContactPoint* point){
   	printf("Hello world.")
   }
   
   void MyContactListener::Persist(const b2ContactPoint* point){
   }
   
   void MyContactListener::Remove(const b2ContactPoint* point){
   
   }

   Posted 2 years ago #
2. 

   onedayitwillmake
   Member

   Sorry, about to go to bed... Don't have time for a proper write up, but this code dump should suffice for now - let me know if you have any questions.

   Here is what I'm using currently

   contactlistener header
   

   #import "SunnyObject.h"
   #import "ContactListener.h"
   #import "Box2D.h"
   #import "b2Contact.h"
   
   class ContactListener : public b2ContactListener
   {
   public:
   	ContactListener();
   
   	void* userData; /// Use this to store application specific body data.
   	void BeginContact(b2Contact* contact);
   	void EndContact(b2Contact* contact);
   };

   Contactlistener implementation

   #import "ContactListener.h"
   #import "Box2D.h"
   #import "b2Contact.h"
   #import "GameScene.h"
   #import "SunnyObject.h"
   
   // Implement contact listener.
   ContactListener::ContactListener(){};
   
   void ContactListener::BeginContact(b2Contact* contact)
   {
   	b2Fixture* fixtureA = contact->GetFixtureA();
   	SunnyObject* actorA = (SunnyObject*) fixtureA->GetBody()->GetUserData();
   
   	b2Fixture* fixtureB = contact->GetFixtureB();
   	SunnyObject* actorB = (SunnyObject*)  fixtureB->GetBody()->GetUserData();
   
   	// Return world box touch
   	if(actorA == nil || actorB == nil) return;
   
   // For debug - randomly scale the objects so u can tell which were hit
   	[actorA setScale:CCRANDOM_0_1() + 0.5];
   	[actorB setScale:CCRANDOM_0_1() + 0.5];
   }
   
   	// Implement contact listener.
   void ContactListener::EndContact(b2Contact* contact)
   {
   		b2Fixture* fixtureA = contact->GetFixtureA();
   		SunnyObject* actorA = (SunnyObject*) fixtureA->GetBody()->GetUserData();
   
   		b2Fixture* fixtureB = contact->GetFixtureB();
   		SunnyObject* actorB = (SunnyObject*)  fixtureB->GetBody()->GetUserData();
   
   		if(actorA == nil || actorB == nil) return;
   }

   SunnyObject is just a class I have that extends atlassprite -

   //In the game
   _contactListener = new ContactListener();
   _world->SetContactListener(_contactListener);

   Posted 2 years ago #
3. 

   onedayitwillmake
   Member

   Oh I just noticed your actual bug you mentioned, that's just a box2d thing - look up this code snippet in box2dsettings.h (not actual spelling)

   #define B2_NOT_USED(x) (x)

   and change it to
   

   #define B2_NOT_USED(x) (void)(x)

   But note, that this is a superfluous change, you can ignore these warnings!

   Oneday,
   http://littlephysics.com

   Posted 2 years ago #
4. 

   phoenixreanimation
   Member

   It works,man.
   You are awesome.

   Posted 2 years ago #
5. 

   fchan
   Member

   @onedayitwillmake: instead of scaling, how would you delete a fixture from there? say for example i want to remove actorA.

   Posted 2 years ago #
6. 

   onedayitwillmake
   Member

   Hi fchan, to remove actorA...

   All my objects have a flag, BOOL _isMarkedForDeletion

   Once that flag is true, the game loop does this....

   -(void) physicsStep:(ccTime)dt
   {
   	int32 velocityIterations = 8;
   	int32 positionIterations = 1;
   
   	// Instruct the world to perform a single step of simulation. It is
   	// generally best to keep the time step and iterations fixed.
   	world->Step(dt, velocityIterations, positionIterations);
   
   	b2Body* node = world->GetBodyList();
   	while(node)
   	{
   		b2Body* b = node;
   		node = node->GetNext();
   
   		// If GetUserData() is null, then it's probably the floor or something else
   		// we're not interested in
   		if (b->GetUserData() != NULL)
   		{
   			// Safely remove a body marked for deletion
   			if(actor._isMarkedForDeletion == YES)
   			{
   				b->SetUserData(NULL);
   				world->DestroyBody(b);
   
   				// Remove from cocos2d
   				AtlasSpriteManager* mgr = (AtlasSpriteManager*) actor.parent;
   				[mgr removeChild:actor cleanup:YES];
   			}
   		}
   	}
   }

   You can't remove an object during a contact, so just get rid of it the next frame.

   Posted 2 years ago #
7. 

   cocos2dbeginner
   Member

   @all + onedayitwillmake

   How do I use the contact listener in HelloWorldScene?

   How can I use this? Please help me! I looked at the breakout tut on rays website but he uses another listener..
   :(

   Posted 1 year ago #

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