ios - 在 cocos2d 中销毁 box2d 主体

Question

我有一张网和一些昆虫，我正在扔网并与昆虫进行碰撞检测并摧毁它们。我使用 bod2d 进行碰撞检测。

世界法

-(void)createWorld
{

 // Define the gravity vector.
    b2Vec2 b_gravity;
    b_gravity.Set(0.0f, -9.8f);

 // Do we want to let bodies sleep?
 // This will speed up the physics simulation
    bool doSleep = true;

 // Construct a world object, which will hold and simulate the rigid bodies.
    world = new b2World(b_gravity);
    world->SetAllowSleeping(doSleep);

    world->SetContinuousPhysics(true);

}

创建网站

-(void) createWeb
{
    freeBodySprite = [CCSprite spriteWithFile:@"web1.png"];
        [self addChild:freeBodySprite z:2 tag:TAG_WEB];

    CGPoint startPos = CGPointMake(100, 320/1.25);

    bodyDef.type = b2_staticBody;
    bodyDef.position = [self toMeters:startPos];
    bodyDef.userData = freeBodySprite;

    float radiusInMeters = ((freeBodySprite.contentSize.width * freeBodySprite.scale/PTM_RATIO) * 1.0f);
    shape.m_radius = radiusInMeters;

    fixtureDef.shape = &shape;
    fixtureDef.density = 0.01f;
    fixtureDef.friction = 0.1f;
    fixtureDef.restitution = 0.1f;

    circularObstacleBody = world->CreateBody(&bodyDef);
    stoneFixture = circularObstacleBody->CreateFixture(&fixtureDef);
        freeBody = circularObstacleBody;
}

我用 spritesheet 创建了我的昆虫动画，然后为那个 Sprite 创建了 b2body

-(b2Body *) createMovingBoxObstacle
{


    //set this to avoid updating this object in the tick schedule
        _ants.userData = (void *)YES;

    b2BodyDef bodyDef_Ant;
    bodyDef_Ant.type = b2_dynamicBody;
    CGPoint startPos = ccp(520,winSize.height/7.6);
    bodyDef_Ant.position = [self toMeters:startPos];
    bodyDef_Ant.userData = _ants;

    b2PolygonShape dynamicBox;
    float tileWidth = ((_ants.contentSize.width * _ants.scale/PTM_RATIO) * 0.5f);
    float tileHeight = ((_ants.contentSize.height * _ants.scale/PTM_RATIO) * 0.5f);
    dynamicBox.SetAsBox(tileWidth, tileHeight);

    b2FixtureDef fixtureDef_Ant;
    fixtureDef_Ant.shape = &dynamicBox;
    fixtureDef_Ant.friction = 0.7;
    fixtureDef_Ant.density = 0.1f;
    fixtureDef_Ant.restitution = 0.7;


    staticBody = world->CreateBody(&bodyDef_Ant);
    staticBody->CreateFixture(&fixtureDef_Ant);

       VAMovingObstacle* moveableObject = [[VAMovingObstacle alloc] init];
       moveableObject.startPoint = ccp(520,winSize.height/7.6);
       moveableObject.endPoint = ccp(-50,winSize.height/7.6);
       moveableObject.transitionTime = 20.0;
       moveableObject.breakTime = 1.0;

    moveableObject.obstacleSprite = _ants;
    moveableObject.physicalBody = staticBody;
    [moveableObject startMovement];

    if (!movingObstacles) {
        movingObstacles = [[NSMutableArray alloc] init];
    }
    [movingObstacles addObject:moveableObject];
    [moveableObject release];
    return staticBody;
}

VAMovingObstacle 是一个帮助 sprite 和 b2body 从左向右移动(runaction)的类

这是我的联系人监听器的 EndContact 方法

void ContactListener::EndContact(b2Contact* contact)
{
    b2Body* bodyA = contact->GetFixtureA()->GetBody();
    b2Body* bodyB = contact->GetFixtureB()->GetBody();

    if (bodyA->GetUserData() != NULL && bodyB->GetUserData() != NULL) {
        CCSprite *spriteA = (CCSprite *) bodyA->GetUserData();
        CCSprite *spriteB = (CCSprite *) bodyB->GetUserData();


        if (spriteA.tag == TAG_WEB && spriteB.tag >= TAG_ANT) {

        }

        else if (spriteA.tag >= TAG_ANT && spriteB.tag == TAG_WEB) {

            [spriteA removeFromParentAndCleanup:YES];
            [[HelloWorldLayer sharedLevel] WebCollisionWithInsect:bodyA];
        }
    }
}

当碰撞发生时，EndContact 方法调用 WebCollisionWithInsect:bodyA

-(void) WebCollisionWithInsect:(b2Body*) bodyT{
            world->DestroyBody(bodyT);
}

在 world->DestroyBody(bodyT) 行它给出一个错误

Assertion failed: (IsLocked() == false), function DestroyBody, file /Users/libs/Box2D/Dynamics/b2World.cpp, line 134.

知道我做错了什么。 ？

已编辑我在 EndContact 中添加了这一行

destroyCollisionDetectionBody = objBody;
didInsectCollideWithWeb = YES;

保留我想销毁的 body 的引用。现在我可以在 if check 上用 tick 方法破坏我的 body 在 tick 方法中添加了这些行

if(didInsectCollideWithWeb)
    {
        [self unschedule:@selector(tick:)];
        [freeBodySprite removeFromParentAndCleanup:YES]; // this is my web
        world->DestroyBody(destroyCollisionDetectionBody);
        world->DestroyBody(freeBody);
        [self createWeb];
        [self schedule:@selector(tick:)];
        didInsectCollideWithWeb = NO;

    }

但现在的问题是，当我破坏我的网络时，即自由体。我无法重新创建它。正如我之前通过调用 [self createWeb] 所做的那样；

Answer 1

您正试图销毁一个正在模拟阶段使用的 box2d 对象(因为在该阶段调用了 EndContact)。模拟阶段是调用世界的 step 方法时执行的阶段。

因此，您应该做的是保持对要删除的 body 对象的引用，并在 box2d 模拟阶段之后(在 step 方法返回之后)执行 WebCollisionWithInsect拥有想要的身材