my project have a UIcollectionView. This Horizontal paging and have four object. I want my collectionView Auto Scroll Paging. which use methods?
As for theory, I just explain the key point. For example, if you want to auto-cycle display 5 images in somewhere, just as ads bar. You can create a UICollectionView with 100 sections, and there're 5 items in every section. After creating UICollectionView, set its original position is equal to the 50th section 0th item(middle of MaxSections ) so that you can scroll to left or right. Don't worry it will ends, because I have reset the position equal to middle of MaxSections when the Timer runs. Never argue with me :" it also will ends when the user keep scrolling by himself" If one find there're only 5 images, will he keep scrolling!? I believe there is few such silly user in this world!
Note: In the following codes,the headerView is UICollectionView,headerNews is data. And I suggest set MaxSections = 100.
Add a NSTimer after custom collectionView(Ensure the UICollectionViewFlowLayout is properly set at first):
- (void)addTimer
{
NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:3.0f target:self selector:@selector(nextPage) userInfo:nil repeats:YES];
[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
self.timer = timer;
}
then implement @selector(nextPage):
- (void)nextPage
{
// 1.back to the middle of sections
NSIndexPath *currentIndexPathReset = [self resetIndexPath];
// 2.next position
NSInteger nextItem = currentIndexPathReset.item + 1;
NSInteger nextSection = currentIndexPathReset.section;
if (nextItem == self.headerNews.count) {
nextItem = 0;
nextSection++;
}
NSIndexPath *nextIndexPath = [NSIndexPath indexPathForItem:nextItem inSection:nextSection];
// 3.scroll to next position
[self.headerView scrollToItemAtIndexPath:nextIndexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];
}
last implement resetIndexPath method:
- (NSIndexPath *)resetIndexPath
{
// currentIndexPath
NSIndexPath *currentIndexPath = [[self.headerView indexPathsForVisibleItems] lastObject];
// back to the middle of sections
NSIndexPath *currentIndexPathReset = [NSIndexPath indexPathForItem:currentIndexPath.item inSection:MaxSections / 2];
[self.headerView scrollToItemAtIndexPath:currentIndexPathReset atScrollPosition:UICollectionViewScrollPositionLeft animated:NO];
return currentIndexPathReset;
}
In order to control NSTimer , you have to implement some other methods and UIScrollView's delegate methods:
- (void)removeTimer
{
// stop NSTimer
[self.timer invalidate];
// clear NSTimer
self.timer = nil;
}
// UIScrollView' delegate method
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
[self removeTimer];
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
[self addTimer];
}