UIImageView使用UICollectionView淡入淡出动画

Question

I have a Horizontal UICollectionView with n number of records. Each cell has an UIImageView which needs to animate the Fadein Fadeout with some TimerInterval. So, i have planned to implement that reload my UICollectionView using NSTimer My code snippet,

....
....
if (collectionTimer) {
    [collectionTimer invalidate];
    collectionTimer = nil;
}
collectionTimer = [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(reloadCollection) userInfo:nil repeats:YES];
....
....

reloadCollection Method

-(void)reloadCollection{
    [_collectionView reloadData];
}

cellForItemAtIndexPath Method

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    ....
    ....
    /* Basic Animation working fine*/
    [UIView animateKeyframesWithDuration:1.0 delay:1.0 options:UIViewKeyframeAnimationOptionAutoreverse animations:^{
        cell.articleImage.image = [UIImage imageNamed:[NSString stringWithFormat:@"%@.jpg", [images objectAtIndex:i]]];
    } completion:nil];

    /* Not working */
    /* [UIView transitionWithView:cell.articleImage duration:1.0f options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
        cell.articleImage.image = [UIImage imageNamed:[NSString stringWithFormat:@"%@.jpg", [images objectAtIndex:i]]];
    } completion:nil]; */
    ....
    ....
}

The basic animation works fine. But, whenever i am trying to implement UIViewAnimationOptionTransitionCrossDissolve with transitionWithView method. It will showing the animation, but immediately one more image loaded because of reloadData calling. How to fix this? How to animate only the images in UICollectionView

Any Idea appreciated!

Answer 1

Well i guess that in your method cellForItemAtIndexPath you are not configuring animation right.

please use this.

[UIView animateKeyframesWithDuration:1.0 delay:0.1 options:UIViewKeyframeAnimationOptionAutoreverse animations:^{
    cell.articleImage.image = [UIImage imageNamed:[NSString stringWithFormat:@"%@.jpg", [images objectAtIndex:i]]];
} completion:nil];

You were not assigning the delay properly to let animation work.

Hope it works for you now. Thanks

Answer 2

My animation work like this:

cell.articleImage.alpha = 0.0;
[UIView animateWithDuration:0.3f animations:^{
     [cell.articleImage setAlpha:1.0];
}];

Answer 3

Try to add the animation for visible cells without reloading the collectionView:

NSArray* visibleCells = [collectionView visibleCells];
[visibleCells enumerateObjectsUsingBlock:^(UICollectionViewCell* cell, NSUInteger idx, BOOL *stop) {
    //TODO: add animation;
}];

Update
To animate new cells, you should start animation after adding cell to window. In cell you can override method didMoveToWindow:

- (void)didMoveToWindow
{
   [super didMoveToWindow];
   if (self.window && self.shouldStartAnimation)
   {
     [self startAnimation];
   }
}

And in ViewController these methods:

    - (void)animateVisibleCells
    {
        NSArray* visibleCells = [self.collectionView visibleCells];
        [visibleCells enumerateObjectsUsingBlock:^(BTCollectionViewCell* cell, NSUInteger idx, BOOL *stop) {
            [cell startAnimation];
        }];
    }


    #define ANIMATION_DURATION (0.3)
    - (void)animateCells
    {
        self.shouldAnimationStart = YES;

        [self animateVisibleCells];

        [NSTimer scheduledTimerWithTimeInterval:ANIMATION_DURATION target:self selector:@selector(endAnimateCells) userInfo:nil repeats:NO];
    }


    - (void)endAnimateCells
    {
        self.shouldAnimationStart = NO;
    }


    - (void)collectionView:(UICollectionView *)collectionView willDisplayCell:(UICollectionViewCell *)cell forItemAtIndexPath:(NSIndexPath *)indexPath
    {
        ((BTCollectionViewCell*)cell).shouldStartAnimation = self.shouldAnimationStart;
    }

But problem with synchronization of the animation continues to be (new animations will starts from 0 time). If you know method to start animation from concrete time, you can use it method in willDisplayCell