我正在使用 cocos2d v1.0.1 和相应的 Box2d 版本。在模拟器中一切正常。它只是一个在触摸位置创建的身体，它会落到地上。但我在设备 iphone4 上运行它，并且对象向上浮动。
为什么会发生这种情况？
重力设置为 -0.3f。我在场景中有另一个动态物体，它应该出现在地面的底部。它只是漂浮起来的触摸物体。睡眠是真的。
我只是将 sleep 设置为 false，现在流动站也浮起来了。但它不应该浮起来。这是我的世界创建方法：
- (void)setupWorld {
b2Vec2 gravity = b2Vec2(0.0f, -0.3f);
bool doSleep = false;
world = new b2World(gravity, doSleep);
}
这是我从init创建的身体：
Box2DSprite *roverSprite = [Box2DSprite spriteWithSpriteFrameName:@"rover.png"];
[self createBoxAtLocation:ccp(100,15) withSize:CGSizeMake(50, 50) forSprite:roverSprite isBox:TRUE];
[sceneSpriteBatchNode addChild:roverSprite];
这是 createBox 方法：
- (void)createBoxAtLocation:(CGPoint)location withSize:(CGSize)size forSprite:(Box2DSprite *)sprite isBox:(BOOL)isBox{
b2BodyDef bodyDef;
bodyDef.type = b2_dynamicBody;
bodyDef.position = b2Vec2(location.x/PTM_RATIO, location.y/PTM_RATIO);
b2Body *body = world->CreateBody(&bodyDef);
//
body->SetUserData(sprite);
sprite.body = body;
b2FixtureDef fixtureDef;
//
if (isBox) {
b2PolygonShape shape;
shape.SetAsBox(sprite.contentSize.width/3/PTM_RATIO,
sprite.contentSize.height/3/PTM_RATIO);
fixtureDef.shape = &shape;
} else {
b2CircleShape shape;
shape.m_radius = sprite.contentSize.width/2/PTM_RATIO;
fixtureDef.shape = &shape;
}
fixtureDef.density = 1.0;
fixtureDef.friction = 1.0;
fixtureDef.restitution = 0.5;
body->CreateFixture(&fixtureDef);
}
同样的方法也用于从这些行创建的触摸创建对象：
-(BOOL) ccTouchBegan:(UITouch *)touch withEvent:(UIEvent *)event {
CGPoint touchLocation = [touch locationInView:[touch view]];
touchLocation = [[CCDirector sharedDirector] convertToGL:touchLocation];
touchLocation = [self convertToNodeSpace:touchLocation];
//b2Vec2 locationWorld = b2Vec2(touchLocation.x/PTM_RATIO, touchLocation.y/PTM_RATIO);
Box2DSprite *sprite = [Box2DSprite spriteWithSpriteFrameName:@"koko1.png"];
[self createBoxAtLocation:touchLocation withSize:CGSizeMake(50, 50) forSprite:sprite isBox:TRUE];
[sceneSpriteBatchNode addChild:sprite];
return TRUE;
}