1.实现滚动缩放
自定义Layout继承
UICollectionViewFlowLayout
@implementation MyCollectionLayout
- (void)prepareLayout{
[super prepareLayout];
self.scrollDirection = UICollectionViewScrollDirectionHorizontal;
self.minimumLineSpacing = 1;
}
- (NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{
NSArray *attrsArr = [super layoutAttributesForElementsInRect:rect];
NSMutableArray *newAttrsArr = [NSMutableArray arrayWithCapacity:attrsArr.count];
CGFloat centerX = self.collectionView.bounds.size.width/2;
for (UICollectionViewLayoutAttributes* attr in attrsArr) {
CGFloat distanceCenter = fabs(attr.center.x - centerX-self.collectionView.contentOffset.x);
CGFloat scale = 1.2- distanceCenter/centerX;
if (scale <0.8) {
scale = 0.8;
}
attr.transform = CGAffineTransformMakeScale(scale, scale);
[newAttrsArr addObject:attr];
self.itemWidth = attr.size.width;
}
return newAttrsArr;
}
- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds{
return true;
}
- (CGPoint)targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset withScrollingVelocity:(CGPoint)velocity {
NSLog(@"before proposedContentOffset==%@",NSStringFromCGPoint(proposedContentOffset));
CGRect rect = CGRectMake(proposedContentOffset.x, 0, self.collectionView.bounds.size.width, self.collectionView.bounds.size.height);
NSArray *attrs = [super layoutAttributesForElementsInRect:rect];
CGFloat collectionViewCenterX = self.collectionView.frame.size.width * 0.5;
CGFloat minDistance = MAXFLOAT;
//找出距离中点最近的item
for (UICollectionViewLayoutAttributes *attr in attrs) {
CGFloat distance = attr.center.x - proposedContentOffset.x - collectionViewCenterX;
NSLog(@"distance ==%f",distance);
if (fabs(distance) < fabs(minDistance)) {
minDistance = distance;
}
}
//位移一段保持居中
proposedContentOffset.x += minDistance;
NSLog(@"after proposedContentOffset==%@",NSStringFromCGPoint(proposedContentOffset));
return proposedContentOffset;
}
@end
2.拖动排序item
这里给collectionview添加一个长按的手势进入拖动状态
- (void)move:(UILongPressGestureRecognizer*)reg{
if (reg.state == UIGestureRecognizerStateBegan) {
[self.collectionView beginInteractiveMovementForItemAtIndexPath:[self.collectionView indexPathForItemAtPoint: [reg locationInView:self.collectionView]]];
cell = (WJLCollectionViewCell*)[self.collectionView cellForItemAtIndexPath:[self.collectionView indexPathForItemAtPoint: [reg locationInView:self.collectionView]]];
}else if (reg.state == UIGestureRecognizerStateChanged){
[self.collectionView updateInteractiveMovementTargetPosition:[reg locationInView:self.collectionView]];
}else if (reg.state == UIGestureRecognizerStateEnded) {
[self.collectionView endInteractiveMovement];
}else{
[self.collectionView cancelInteractiveMovement];
}
}
- (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{
//处理移动后的逻辑
}
3.瀑布流