在 cocos2d 3.1 中拖放物理体？

Question

我是cocos2d v3.1的新手

如何在cocos2d v3.1中拖放Physics body。

然后是如何检查两个物理体之间的碰撞和检测。

提前谢谢你

Answer 1

首先，您需要一个名为 CCTouchJoint 的类。

CCTouchJoint.h

#import "Box2D.h"

@interface CCTouchJoint : NSObject
{
@public
b2MouseJoint *mouseJoint;
UITouch *touch;
}
 @property (assign) b2MouseJoint *mouseJoint;
 @property (nonatomic, retain) UITouch *touch;

- (id)initLocal:(UITouch *)touch withMouseJoint:(b2MouseJoint *)mouseJoint;
+ (id)touch:(UITouch *)touch withMouseJoint:(b2MouseJoint *)mouseJoint;

 // Public methods

/**
* Destroy the touch joint in the Box2d world.
*/
 - (void)destroyTouchJoint;

@end

CCTouchJoint.mm

#import "CCTouchJoint.h"

 @implementation CCTouchJoint
 @synthesize mouseJoint;
 @synthesize touch;

- (void)dealloc
 {
  [touch release];
  [super dealloc];
  }

- (id)initLocal:(UITouch *)_touch withMouseJoint:(b2MouseJoint *)_mouseJoint
 {
  if ((self = [super init]))
  {
    self.touch = _touch;
    mouseJoint = _mouseJoint;
 }
 return self;
 }

+ (id)touch:(UITouch *)_touch withMouseJoint:(b2MouseJoint *)_mouseJoint
 {
 return [[self alloc] initLocal:_touch withMouseJoint:_mouseJoint];
  }

#pragma mark -
 #pragma mark CCTouchJoint Public Methods

 - (void)destroyTouchJoint
   {
  if (mouseJoint != NULL)
   {
    mouseJoint->GetBodyA()->GetWorld()->DestroyJoint(mouseJoint);
   }
 } 

#pragma mark CCTouchJoint Private Methods

@end

第二。 self.touchEnabled = YES; 你需要 NSMutableArray *touchJointList; b2Body *groundBody 和 b2Body *b; 这个触摸代码：

  - (void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
 {
   NSSet *allTouches = [event allTouches];


  for(UITouch *touch in allTouches)
  {
    CGPoint location = [touch locationInView:touch.view];

    location = [[CCDirector sharedDirector] convertToGL:location];
    b2Vec2 worldLoc = b2Vec2(ptm(location.x), ptm(location.y));

    for (b = world->GetBodyList(); b; b = b->GetNext())
    {
        if (b->GetType() == b2_dynamicBody)


            for (b2Fixture *f = b->GetFixtureList(); f; f = f->GetNext())
            {    


                // Hit!
                if (f->TestPoint(worldLoc))
                {

                    /// Mouse joint definition
                    b2MouseJointDef md;
                    md.bodyA = groundBody;
                    md.bodyB = b;
                    md.target = worldLoc;
                    md.maxForce = 3000.0 * b->GetMass();
                    md.dampingRatio = 5;
                    md.frequencyHz = 60;


                    // Joint of bodys
                    b2MouseJoint *m_touchJoint;
                    m_touchJoint = (b2MouseJoint *)world->CreateJoint(&md);

                    CCTouchJoint *tj = [CCTouchJoint touch:touch withMouseJoint:m_touchJoint];
                    [touchJointList addObject:tj];

                    b->SetAwake(true);

                    }
                    break;
                }
            }
            }
       }




- (void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
  {

   for (CCTouchJoint *tj in touchJointList)
   {
    if([tj.touch phase] == UITouchPhaseMoved)
      {
        // Update if it is moved
        CGPoint location = [tj.touch locationInView:tj.touch.view];
        location = [[CCDirector sharedDirector] convertToGL:location];

        b2Vec2 worldLocation = b2Vec2(ptm(location.x), ptm(location.y));
        tj.mouseJoint->SetTarget(worldLocation);
        }
    }
 }

  - (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
  {

  NSSet *allTouches = [event allTouches];

   NSMutableArray *discardedItems = [NSMutableArray array];

   for(UITouch *touch in allTouches)
     {
    for (CCTouchJoint *tj in touchJointList)
    {
        if (tj.touch == touch)
        {
            // Defensive programming - assertion
            NSAssert([tj isKindOfClass:[CCTouchJoint class]], @"node is not a touchJoint!");

            // If safe - loop through
            if ([tj.touch phase] == UITouchPhaseEnded)
            {
                [discardedItems addObject:tj];

                [tj destroyTouchJoint];
                [tj release];
            }
        }
    }

 }


  [touchJointList removeObjectsInArray:discardedItems];

  }

  - (void)ccTouchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
 {

  [touchJointList removeAllObjects];

    }

记住：更改 md.dampingRatio 和 md.frequencyHz 会影响鼠标关节的行为。

Answer 2

尝试以下链接进行碰撞检测。对你有帮助。

http://www.cocos2d-x.org/wiki/Chapter_5_-_How_to_Detect_the_Collisions