La animation de UICollectionView contentOffset no muestra celdas no visibles

Estoy trabajando en algunas funciones tipo ticker y estoy usando una UICollectionView . Originalmente era un scrollView, pero creemos que una colecciónView facilitará agregar / eliminar celdas.

Estoy animando la colecciónView con lo siguiente:

 - (void)beginAnimation { [UIView animateWithDuration:((self.collectionView.collectionViewLayout.collectionViewContentSize.width - self.collectionView.contentOffset.x) / 75) delay:0 options:(UIViewAnimationOptionCurveLinear | UIViewAnimationOptionRepeat | UIViewAnimationOptionBeginFromCurrentState) animations:^{ self.collectionView.contentOffset = CGPointMake(self.collectionView.collectionViewLayout.collectionViewContentSize.width, 0); } completion:nil]; } 

Esto funciona bien para la vista de desplazamiento, y la animation está sucediendo con la vista de colección. Sin embargo, solo se muestran las celdas que están visibles al final de la animation. Ajustar el contenido del juego no provoca la cellForItemAtIndexPath de cellForItemAtIndexPath . ¿Cómo puedo hacer que las celdas se muestren cuando cambia el contenido?

EDIT: Para un poco más de reference (no estoy seguro si es de mucha ayuda):

 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath { TickerElementCell *cell = (TickerElementCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"TickerElementCell" forIndexPath:indexPath]; cell.ticker = [self.fetchedResultsController objectAtIndexPath:indexPath]; return cell; } - (void)controllerDidChangeContent:(NSFetchedResultsController *)controller { // ... [self loadTicker]; } - (void)loadTicker { // ... if (self.animating) { [self updateAnimation]; } else { [self beginAnimation]; } } - (void)beginAnimation { if (self.animating) { [self endAnimation]; } if ([self.tickerElements count] && !self.animating && !self.paused) { self.animating = YES; self.collectionView.contentOffset = CGPointMake(1, 0); [UIView animateWithDuration:((self.collectionView.collectionViewLayout.collectionViewContentSize.width - self.collectionView.contentOffset.x) / 75) delay:0 options:(UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionRepeat | UIViewAnimationOptionBeginFromCurrentState) animations:^{ self.collectionView.contentOffset = CGPointMake(self.collectionView.collectionViewLayout.collectionViewContentSize.width, 0); } completion:nil]; } } 

Simplemente debe agregar [self.view layoutIfNeeded]; dentro del bloque de animation, así:

 [UIView animateWithDuration:((self.collectionView.collectionViewLayout.collectionViewContentSize.width - self.collectionView.contentOffset.x) / 75) delay:0 options:(UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionRepeat | UIViewAnimationOptionBeginFromCurrentState) animations:^{ self.collectionView.contentOffset = CGPointMake(self.collectionView.collectionViewLayout.collectionViewContentSize.width, 0); [self.view layoutIfNeeded]; } completion:nil]; 

Podría intentar usar un CADisplayLink para manejar la animation usted mismo. Esto no es muy difícil de configurar ya que está utilizando una curva de animation lineal de todos modos. Aquí hay una implementación básica que puede funcionar para usted:

 @property (nonatomic, strong) CADisplayLink *displayLink; @property (nonatomic, assign) CFTimeInterval lastTimerTick; @property (nonatomic, assign) CGFloat animationPointsPerSecond; @property (nonatomic, assign) CGPoint finalContentOffset; -(void)beginAnimation { self.lastTimerTick = 0; self.animationPointsPerSecond = 50; self.finalContentOffset = CGPointMake(..., ...); self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(displayLinkTick:)]; [self.displayLink setFrameInterval:1]; [self.displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes]; } -(void)endAnimation { [self.displayLink invalidate]; self.displayLink = nil; } -(void)displayLinkTick { if (self.lastTimerTick = 0) { self.lastTimerTick = self.displayLink.timestamp; return; } CFTimeInterval currentTimestamp = self.displayLink.timestamp; CGPoint newContentOffset = self.collectionView.contentOffset; newContentOffset.x += self.animationPointsPerSecond * (currentTimestamp - self.lastTimerTick) self.collectionView.contentOffset = newContentOffset; self.lastTimerTick = currentTimestamp; if (newContentOffset.x >= self.finalContentOffset.x) [self endAnimation]; } 

Sospecho que UICollectionView está tratando de mejorar el performance esperando hasta el final del desplazamiento antes de actualizar.

Tal vez podrías dividir la animation en chucks, aunque no estoy seguro de lo suave que sería eso.

O tal vez llamando a setNeedsDisplay periódicamente durante el desplazamiento?

Alternativamente, tal vez este reemploop para UICollectionView querrá que lo necesite o, de lo contrario, se puede modificar para hacerlo:

https://github.com/steipete/PSTCollectionView

Aquí hay una implementación rápida, con comentarios que explican por qué esto es necesario.

La idea es la misma que en la respuesta de Devdavid, solo el enfoque de implementación es diferente.

 /* Animated use of `scrollToContentOffset:animated:` doesn't give enough control over the animation duration and curve. Non-animated use of `scrollToContentOffset:animated:` (or contentOffset directly) embedded in an animation block gives more control but interfer with the internal logic of UICollectionView. For example, cells that are not visible for the target contentOffset are removed at the beginning of the animation because from the collection view point of view, the change is not animated and the cells can safely be removed. To fix that, we must control the scroll ourselves. We use CADisplayLink to update the scroll offset step-by-step and render cells if needed alongside. To simplify, we force a linear animation curve, but this can be adapted if needed. */ private var currentScrollDisplayLink: CADisplayLink? private var currentScrollStartTime = Date() private var currentScrollDuration: TimeInterval = 0 private var currentScrollStartContentOffset: CGFloat = 0.0 private var currentScrollEndContentOffset: CGFloat = 0.0 // The curve is hardcoded to linear for simplicity private func beginAnimatedScroll(toContentOffset contentOffset: CGPoint, animationDuration: TimeInterval) { // Cancel previous scroll if needed resetCurrentAnimatedScroll() // Prevent non-animated scroll guard animationDuration != 0 else { logAssertFail("Animation controlled scroll must not be used for non-animated changes") collectionView?.setContentOffset(contentOffset, animated: false) return } // Setup new scroll properties currentScrollStartTime = Date() currentScrollDuration = animationDuration currentScrollStartContentOffset = collectionView?.contentOffset.y ?? 0.0 currentScrollEndContentOffset = contentOffset.y // Start new scroll currentScrollDisplayLink = CADisplayLink(target: self, selector: #selector(handleScrollDisplayLinkTick)) currentScrollDisplayLink?.add(to: RunLoop.current, forMode: .commonModes) } @objc private func handleScrollDisplayLinkTick() { let animationRatio = CGFloat(abs(currentScrollStartTime.timeIntervalSinceNow) / currentScrollDuration) // Animation is finished guard animationRatio < 1 else { endAnimatedScroll() return } // Animation running, update with incremental content offset let deltaContentOffset = animationRatio * (currentScrollEndContentOffset - currentScrollStartContentOffset) let newContentOffset = CGPoint(x: 0.0, y: currentScrollStartContentOffset + deltaContentOffset) collectionView?.setContentOffset(newContentOffset, animated: false) } private func endAnimatedScroll() { let newContentOffset = CGPoint(x: 0.0, y: currentScrollEndContentOffset) collectionView?.setContentOffset(newContentOffset, animated: false) resetCurrentAnimatedScroll() } private func resetCurrentAnimatedScroll() { currentScrollDisplayLink?.invalidate() currentScrollDisplayLink = nil } 

Use :scrollToItemAtIndexPath lugar:

 [UIView animateWithDuration:duration animations:^{ [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UICollectionViewScrollPositionNone animated:NO]; }];