Smoothly drag a Sprite in cocos2d - iPhone

Question

I have implemented a drag on a sprite object as follows..

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

UITouch * touch = [touches anyObject];
CGPoint location = [[Director sharedDirector] convertCoordinate: [touch locationInView:touch.view]];    
[diskSprite setPosition:ccp(location.x , location.y )];
return kEventHandled;
}

but this dragging is not smooth..... when i drag fast with my thumb the object left from the path.

Thanks

Solution 1

Probably a little bit late but I was searching for a similar thing. I found this great Tutorial which explained everything: http://www.raywenderlich.com/2343/how-to-drag-and-drop-sprites-with-cocos2d

- (void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event {       
    CGPoint touchLocation = [self convertTouchToNodeSpace:touch];

    CGPoint oldTouchLocation = [touch previousLocationInView:touch.view];
    oldTouchLocation = [[CCDirector sharedDirector] convertToGL:oldTouchLocation];
    oldTouchLocation = [self convertToNodeSpace:oldTouchLocation];

    CGPoint translation = ccpSub(touchLocation, oldTouchLocation);    
    CGPoint newPos = ccpAdd(mySpriteToMove.position, translation);
    mySpriteToMove.position = newPos;
}

Solution 2

I had this same issue with my game. Dragging operations appeared jerky. I believe the reason is that touch events aren't generated fast enough to give a smooth appearance.

To solve the problem I smoothed the motion out by running an action on the sprite toward the desired location, instead of setting the position immediately.