IOS--常用Banner循环滚动实现

实现步骤：

1.先整合数据源

//循环滚动，增加尾部和首部的数据源用以实现循环的视觉错觉
//如原@[a,b,c]，整合成@[c,a,b,c,a]
  self.lastX = 0;
  NSMutableArray *tmpArray = [NSMutableArray arrayWithArray:URLArray];
  [tmpArray addObject:[URLArray firstObject]];
  [tmpArray insertObject:[URLArray lastObject] atIndex:0];
  self.urlArray = [NSArray arrayWithArray:tmpArray];
  [self.collectionView reloadData];
 //collectionView刷新数据后再显示第一个数据页面
   [self.collectionView performBatchUpdates:^{
        [self.collectionView reloadData];
   } completion:^(BOOL finished) {
   [self.collectionView selectItemAtIndexPath:[NSIndexPath indexPathForItem:1 inSection:0] animated:NO scrollPosition:UICollectionViewScrollPositionLeft];
   //开启滚动计时器
   [self startTimer];
   }];

2.计时器的设计

//开启计时器
- (void)startTimer {
[self stopTimer];
self.timer = [MSWeakTimer scheduledTimerWithTimeInterval:3 target:self selector:@selector(scrollToNextPage) userInfo:nil repeats:YES dispatchQueue:dispatch_get_main_queue()];
}
//collectionView滚动至下一页
- (void)scrollToNextPage {
NSIndexPath *indexpath = [self.collectionView indexPathForItemAtPoint:self.collectionView.contentOffset];
NSIndexPath *incrementPath = nil;

if (indexpath.item == [self.collectionView numberOfItemsInSection:0] - 1) {
    //滚动至尾部
    incrementPath = [NSIndexPath indexPathForItem:0 inSection:0];
} else if ([self.collectionView numberOfItemsInSection:0] == 0) {
    //滚动至首部
    incrementPath = [NSIndexPath indexPathForItem:0 inSection:0];
} else {
    //中间部分滚动
    incrementPath = [NSIndexPath indexPathForItem:indexpath.item + 1 inSection:0];
}
[self.collectionView scrollToItemAtIndexPath:incrementPath atScrollPosition:UICollectionViewScrollPositionRight animated:YES];
}   

3.循环滚动实现

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
    //banner无限循环快速滑动
    CGFloat currX = scrollView.contentOffset.x;
    CGFloat pageX = currX - scrollView.frame.size.width;
    NSInteger currCount = self.urlArray.count;
    if (currCount > 1) {
        if ((currX - _lastX) >= 0) {
            //Banner右边区域的滑动
            if(currX > (currCount-2)*scrollView.frame.size.width){
                _lastX = 0;
                [scrollView setContentOffset:CGPointMake(currX-(currCount-2)*scrollView.frame.size.width, 0)];
            }
            //pageVC滑动
            if (currX < scrollView.frame.size.width) {
                pageX = (currCount-2)*scrollView.frame.size.width;
            }
        }else{
            //Banner左边区域的滑动
            if(currX > (currCount-2)*scrollView.frame.size.width){
                _lastX = 0;
                [scrollView setContentOffset:CGPointMake(currX-(currCount-2)*scrollView.frame.size.width, 0)];
            }else if (currX < scrollView.frame.size.width) {
                _lastX = currCount*scrollView.frame.size.width;
                [scrollView setContentOffset:CGPointMake(currX+(currCount-2)*scrollView.frame.size.width, 0)];
            }
            //pageVC滑动
            if (currX < scrollView.frame.size.width) {
                pageX = (currCount-2)*scrollView.frame.size.width;
            }else if (currX > (currCount-2)*scrollView.frame.size.width){
                pageX = 0;
            }
        }
        int currPage = (int)(pageX/scrollView.frame.size.width);
        self.pageControl.currentPage = currPage;
    }
}