Question

I have a set of frames that I need to show in a sequence one after the other but instead of simply erasing the previous frame and drawing the next one, I need to fade out the previous frame and fade in the new one simultaneously.

What is the best way to achieve this in cocos2d?

Answer 1

- (void) showFirstSpriteWithFade
{
    if( [m_sprites count] > 0 )
    {
        CCSprite* spriteToShow = [m_sprites objectAtIndex: 0];
        [m_sprites removeObjectAtIndex: 0];

        id showAction = [CCSequence actions: [CCFadeIn actionWithDuration: fadeInDuration],
                                             [CCFadeOut actionWithDuration: fadeOutDuration],
                                             [CCCallFunc actionWithTarget: self selector:@selector(showFirstSpriteWithFade)],
                                             nil];
       [spriteToShow runAction: showAction];
    }
}

this will work if you wil store all your sprites in array m_sprites. in this case all sprites must be added to the parent to be shown one by one. you can improve this code if you want, for example, use just one sprite and change it’s texture each time.

if you wanna show pictures forever, you can try something like this

- (void) showNextSpriteWithFade
{
        m_shownSpriteIndex++;
        if( m_shownSpriteIndex == [m_sprites count] )
        {
            m_shownSpriteIndex = 0;
        }

        CCSprite* spriteToShow = [m_sprites objectAtIndex: m_shownSpriteIndex];

        id showAction = [CCSequence actions: [CCFadeIn actionWithDuration: fadeInDuration],
                                             [CCFadeOut actionWithDuration: fadeOutDuration],
                                             [CCCallFunc actionWithTarget: self selector:@selector(showNextSpriteWithFade)],
                                             nil];
       [spriteToShow runAction: showAction];

}