Adding and touching multiple sprites in cocos2d - objective-c

Question

I have a class where I add multiple sprites as shown in the code below:
CCSprite *b = [CCSprite spriteWithFile:#"b"];
b.position = ccp(100, 160);
CCSprite *b2 = [CCSprite spriteWithFile:#"b2.png"];
b2.position = ccp(115, 150);
CCSprite *b3 = [CCSprite spriteWithFile:#"b3.png"];
b.position = ccp(200, 150);
CCSprite *b4 = [CCSprite spriteWithFile:#"b4.png"];
b4.position = ccp(220, 145);
b.anchorPoint = ccp(0.98, 0.05);
b2.anchorPoint = ccp(0.03, 0.05);
b3.anchorPoint = ccp(0.03, 0.05);
b4.anchorPoint = ccp(0.95, 0.05);
[self addChild:b z:1 tag:1];
[self addChild:b2 z:1 tag:2];
[self addChild:b3 z:1 tag:3];
[self addChild:b4 z:1 tag:4];
Here's the code for the touch event:
-(void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
NSSet *allTouch = [event allTouches];
UITouch *touch = [[allTouch allObjects]objectAtIndex:0];
CGPoint location = [touch locationInView:[touch view]];
location = [[CCDirector sharedDirector]convertToGL:location];
//Swipe Detection - Beginning point
beginTouch = location;
for(int i = 0; i < [hairArray count]; i++)
{
CCSprite *sprite = (CCSprite *)[hairArray objectAtIndex:i];
if(CGRectContainsPoint([sprite boundingBox], location))
{
//selectedSprite is a sprite declared on the header file
selectedSprite = sprite;
}
}}
-(void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
//Move touched sprite
NSSet *allTouch = [event allTouches];
UITouch *touch = [[allTouch allObjects]objectAtIndex:0];
CGPoint location = [touch locationInView:[touch view]];
location = [[CCDirector sharedDirector]convertToGL:location];
if(selectedSprite != nil)
{
selectedSprite.position = ccp(location.x, location.y);
}}
-(void) ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
//End point of sprite after dragged
NSSet *allTouch = [event allTouches];
UITouch *touch = [[allTouch allObjects]objectAtIndex:0];
CGPoint location = [touch locationInView:[touch view]];
location = [[CCDirector sharedDirector]convertToGL:location];
endTouch = location;
posX = endTouch.x;
//Minimum swipe length
posY = ccpDistance(beginTouch, endTouch);
[self moveSprite];}
Now, the actions itself work just fine but the trouble I'm having is that if I want to drag b2, I have to drag b3 and b4 first. I'm not sure if it has anything to do with the z-index or it is because of the transparent areas that is present for each sprite. Is there something I'm missing here?

Answer 1

if(CGRectContainsPoint([sprite boundingBox], location))
{
//selectedSprite is a sprite declared on the header file
selectedSprite = sprite;
}
This code updates the currently selected sprite as soon as a new one is found while looping on all sprites. This means that if 3 sprites overlap you will get that the selected one is the last one in the array of nodes of the parent.
You can't make any assumptions on the orders so this is not clearly what you want, you have to decide a policy to give sprites priority. Mind that editing the anchorPoint may alter the position of the sprite compared to the bounding box (so that the bounding box is even outside the sprite).
To be sure of it you should enable:
#define CC_SPRITE_DEBUG_DRAW 1
in ccConfig.h. This will render bounding boxes around sprites.