碰撞检测在几个精灵之后变得非常慢

Question

我在cocos2d中有以下方法在sprite之间进行一些碰撞检测。 我能够阻止阵列_车辆中的“车辆”精灵，之后这种方法会阻止车辆从同一方向后方飞来。

现在，当我停下车辆并且“几乎碰撞”的动作生效时帧速率很快下降......为什么会这样？

-(void)doCollisionDetection {
    if (currentVehicle > 0) {
        for (Vehicle *vehicle in _vehicles) {
            int i = [_vehicles indexOfObject:vehicle];
            CGRect Rect1 = CGRectMake(vehicle.position.x - (vehicle.vehicleWidth/2), 
                                      vehicle.position.y - (vehicle.vehicleHeight/2), 
                                      vehicle.vehicleWidth, 
                                      vehicle.vehicleHeight);


            for (Vehicle *vehicletoCheck in _vehicles) {
                int l = [_vehicles indexOfObject:vehicletoCheck];
                if (l == i) { break; }

                CGRect TouchingRect2 = CGRectMake(vehicletoCheck.position.x - (vehicletoCheck.vehicleWidth/2), 
                                                  vehicletoCheck.position.y - (vehicletoCheck.vehicleHeight/2), 
                                                  vehicletoCheck.vehicleWidth, 
                                                  vehicletoCheck.vehicleHeight);

                CGRect TouchingRectWithPadding = CGRectMake(vehicletoCheck.position.x - (vehicletoCheck.vehicleWidth/2)-10, 
                                                  vehicletoCheck.position.y - (vehicletoCheck.vehicleHeight/2)-10, 
                                                  vehicletoCheck.vehicleWidth + 20, 
                                                  vehicletoCheck.vehicleHeight + 20);

                if (CGRectIntersectsRect(Rect1, TouchingRect2))
                {
                    CCLOG(@"Collision detected: %i is touching %i",i,l);
                    [[CCDirector sharedDirector] pause];
                }


                if ( vehicletoCheck.GoDirection == vehicle.GoDirection && CGRectIntersectsRect(Rect1, TouchingRectWithPadding))
                {
                    CCLOG(@"Almost Collided: %i is touching %i",i,l);
                    vehicletoCheck.state = kVehicleStateStopped;
                    vehicle.state = kVehicleStateStopped;
                    break;
                }



            }


            // now check if the vehicle has made it
            if (vehicle.position.x < 0-(vehicle.vehicleWidth) || vehicle.position.x > screenSize.width + (vehicle.vehicleWidth) || vehicle.position.y < 0 - (vehicle.vehicleHeight) || vehicle.position.y > screenSize.height + (vehicle.vehicleHeight)) {
                [vehicle removeFromParentAndCleanup:YES];
                [_vehicles removeObject:vehicle];
            }


        }
    }
}