iOS使用UICollectionView实现列表头部拉伸效果

//// CustomCollectionViewFlowLayout.m// //// Created by GongHui_YJ on 16/8/4.// Copyright © 2016年 Yangjian. All rights reserved.//#import "CustomCollectionViewFlowLayout.h"@implementation CustomCollectionViewFlowLayout- (BOOL)shouldInvalidateLayoutForBoundsChange:(CGRect)newBounds{  return YES;}- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {  UICollectionView *collectionView = [self collectionView];  UIEdgeInsets insets = [collectionView contentInset];  CGPoint offset = [collectionView contentOffset];  CGFloat minY = -insets.top;  NSArray *attributes = [super layoutAttributesForElementsInRect:rect];  if (offset.y < minY) {    CGSize headerSize = [self headerReferenceSize];    CGFloat deltaY = fabsf(offset.y - minY);    for (UICollectionViewLayoutAttributes *attrs in attributes) {      if ([attrs representedElementKind] == UICollectionElementKindSectionHeader) {        CGRect headerRect = [attrs frame];        headerRect.size.height = MAX(minY, headerSize.height + deltaY);        headerRect.origin.y = headerRect.origin.y - deltaY;        [attrs setFrame:headerRect];        break;      }    }  }  return attributes;}@end

// 创建collectionView  CustomCollectionViewFlowLayout *flowLayout=[[CustomCollectionViewFlowLayout alloc] init];  [flowLayout setSectionInset:UIEdgeInsetsMake(0, 0, 10, 0)];  [flowLayout setItemSize:CGSizeMake(kScreenWidth / collectionCellW, kScreenWidth / collectionCellW)];  [flowLayout setHeaderReferenceSize:CGSizeMake(kScreenWidth, userInfoImageViewH)];  [flowLayout setFooterReferenceSize:CGSizeMake(kScreenWidth, 83)];  [flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];  [flowLayout setMinimumInteritemSpacing:0.0];  [flowLayout setMinimumLineSpacing:0.0];  self.homeCollectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 0, kScreenWidth, kScreenHeight - 44)collectionViewLayout:flowLayout];  self.homeCollectionView.backgroundColor = kViewBackgroundColor;  self.homeCollectionView.alwaysBounceVertical = YES;  self.homeCollectionView.showsVerticalScrollIndicator = NO;  //设置代理  self.homeCollectionView.delegate = self;  self.homeCollectionView.dataSource = self;  [self.view addSubview:self.homeCollectionView];  // 注册表头  [self.homeCollectionView registerClass:[YJHeaderCollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:kCollectionHeaderView];  // 注册表尾  [self.homeCollectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:kCollectionFooterView];

//// CustomCollectionViewFlowLayout.swift// //// Created by GongHui_YJ on 16/8/4.// Copyright © 2016年YangJian. All rights reserved.//import UIKitclass CustomCollectionViewFlowLayout: UICollectionViewFlowLayout {  override func shouldInvalidateLayoutForBoundsChange(newBounds: CGRect) -> Bool {    return true  }  override func layoutAttributesForElementsInRect(rect: CGRect) -> [UICollectionViewLayoutAttributes]? {    let collectionView = self.collectionView    let insets = collectionView?.contentInset    let offset = collectionView?.contentOffset    let minY = -((insets?.top)!)    let attributesArray = super.layoutAttributesForElementsInRect(rect)    if offset!.y < minY {      let headerSize = self.headerReferenceSize      let deltaY = CGFloat(fabsf(Float((offset?.y)! - CGFloat(minY))))      for attrs:UICollectionViewLayoutAttributes in attributesArray! {        if attrs.representedElementKind == UICollectionElementKindSectionHeader {          var headerRect = attrs.frame          headerRect.size.height = max(minY, headerSize.height + deltaY)          headerRect.origin.y = headerRect.origin.y - deltaY          attrs.frame = headerRect          break        }      }    }    return attributesArray  }}

let customFlowLayout = CustomCollectionViewFlowLayout()  customFlowLayout.headerReferenceSize = CGSizeMake(kScreenWidth, 203)  customFlowLayout.footerReferenceSize = CGSizeMake(kScreenWidth, 83)  customFlowLayout.minimumInteritemSpacing = 0  customFlowLayout.minimumLineSpacing = 0  customFlowLayout.itemSize = CGSizeMake(kScreenWidth / 3.000006, kScreenWidth / 3.00006)  customFlowLayout.sectionInset = UIEdgeInsetsMake(0, 0, 10, 0)  self.homeCollectionView.setCollectionViewLayout(customFlowLayout, animated: true)  self.homeCollectionView.backgroundColor = kViewBackgroundColor  self.homeCollectionView.alwaysBounceVertical = true  let nib = UINib(nibName: "CommonCollectionViewCell", bundle: nil)  self.homeCollectionView.registerNib(nib, forCellWithReuseIdentifier: cellId)  // 注册表头表尾  let headerNib = UINib(nibName: "HeaderCollectionReusableView", bundle: nil)  self.homeCollectionView.registerNib(headerNib, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: collectionHeaderId)  self.homeCollectionView.registerClass(UICollectionReusableView.classForCoder(), forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier: collectionFooterId)