iOS UICollectionView 在滚动时停在某个item位置上
方法一：实现UIScrollView的代理，然后实现下面这个方法
#pragma mark - UIScrollViewDelegate
//预计出大概位置，经过精确定位获得准备位置
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset{
CGPoint targetOffset = [self nearestTargetOffsetForOffset:*targetContentOffset];
targetContentOffset->x = targetOffset.x;
targetContentOffset->y = targetOffset.y;
}
//计算落在哪个item上
- (CGPoint)nearestTargetOffsetForOffset:(CGPoint)offset
{
CGFloat pageSize = itemSpacing + itemWidth;
//四舍五入
NSInteger page = roundf(offset.x / pageSize);
CGFloat targetX = pageSize * page;
return CGPointMake(targetX, offset.y);
}
方法二：重写UICollectionViewFlowLayout
参考文献：http://tech.glowing.com/cn/practice-in-uiscrollview/
---------------------
作者：C_calary
来源：CSDN
原文：https://blog.csdn.net/C_calary/article/details/78891724
版权声明：本文为博主原创文章，转载请附上博文链接！
UICollectionView横向移动时，且UICollectionView.page = yes只显示一个Cell 移动时姑且计算划至第几个cell
#pragma mark - collectionView
- (UICollectionView *)collectionView
{
if (!_collectionView) {
UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
_collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, screenHeight - kTopHeight - Height_BottomView) collectionViewLayout:layout];
_collectionView.dataSource = self;
_collectionView.delegate = self;
_collectionView.pagingEnabled = YES;
// _collectionView.scrollEnabled = !GetAnswernextque; // 如果只能滑动至下一题取消滚动效果
[_collectionView registerClass:[AnswerCollectionViewCell class] forCellWithReuseIdentifier:@"AnswerCollectionViewCell"];
_collectionView.backgroundColor = [UIColor whiteColor];
_collectionView.showsVerticalScrollIndicator = NO;
_collectionView.showsHorizontalScrollIndicator = NO;
[self.view addSubview:_collectionView];
}
return _collectionView;
}
#pragma mark - UICollectionViewDelegate
//预计出大概位置，经过精确定位获得准备位置
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset{
CGPoint targetOffset = [self nearestTargetOffsetForOffset:*targetContentOffset];
targetContentOffset->x = targetOffset.x;
targetContentOffset->y = targetOffset.y;
// self.currentIndexPath
NSInteger index = targetOffset.x/screenWidth;
DLog(@"---------%ld",index);
self.currentIndexPath = [NSIndexPath indexPathForItem:index inSection:0];
self.lbPageIndex.text = [NSString stringWithFormat:@"%li/%li",self.currentIndexPath.item,self.dataSource.count];
}
//计算落在哪个item上
- (CGPoint)nearestTargetOffsetForOffset:(CGPoint)offset
{
CGFloat pageSize = screenWidth;
//四舍五入
NSInteger page = roundf(offset.x / pageSize);
CGFloat targetX = pageSize * page;
return CGPointMake(targetX, offset.y);
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
CGPoint offsetPoint = scrollView.contentOffset;
self.currentIndexPath = [NSIndexPath indexPathForItem:offsetPoint.x/(screenWidth) inSection:0];
self.lbPageIndex.text = [NSString stringWithFormat:@"%li/%li",self.currentIndexPath.item,self.dataSource.count];
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
CGPoint offsetPoint = scrollView.contentOffset;
self.currentIndexPath = [NSIndexPath indexPathForItem:offsetPoint.x/(screenWidth) inSection:0];
self.lbPageIndex.text = [NSString stringWithFormat:@"%li/%li",self.currentIndexPath.item,self.dataSource.count];
}
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView {
CGPoint offsetPoint = scrollView.contentOffset;
self.currentIndexPath = [NSIndexPath indexPathForItem:offsetPoint.x/(screenWidth) inSection:0];
self.lbPageIndex.text = [NSString stringWithFormat:@"%li/%li",self.currentIndexPath.item,self.dataSource.count];
}
#pragma mark - FlipPageDelegate
- (void)flipToNextPage{
CGPoint offsetPoint = self.collectionView.contentOffset;
NSInteger pageIndex = offsetPoint.x / screenWidth;
if (pageIndex < self.dataSource.count - 1) {
pageIndex++;
NSIndexPath *curIndexPath = [NSIndexPath indexPathForItem:pageIndex inSection:0];
self.currentIndexPath = curIndexPath;
self.lbPageIndex.text = [NSString stringWithFormat:@"%li/%li",pageIndex,self.dataSource.count];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:pageIndex inSection:0];
[self.collectionView scrollToItemAtIndexPath:indexPath atScrollPosition:UICollectionViewScrollPositionLeft animated:YES];
}else{
[ToolUtils showSuccess:@"已经是最后一页"];
}
}
