iOS使用UICollectionView實(shí)現(xiàn)列表頭部拉伸效果

更新時間：2018年05月08日 15:01:14 作者：Break__Self

這篇文章主要介紹了iOS使用UICollectionView實(shí)現(xiàn)列表頭部拉伸效果，OC和Swift兩個版本，具有一定的參考價值，感興趣的小伙伴們可以參考一下

本文實(shí)例為大家分享了iOS實(shí)現(xiàn)列表下拉放大效果展示的具體代碼，供大家參考，具體內(nèi)容如下

先看效果圖

突然發(fā)現(xiàn)沒有做出來之前都覺得蠻難的，做出來之后就覺得So Easy 大家都有這樣的感觸吧

做這個就重寫 UICollectionViewFlowLayout 的幾個方法就可以

OC版本

創(chuàng)建一個類 CustomCollectionViewFlowLayout 繼承 UICollectionViewFlowLayout

//
// 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

在控制器中使用先導(dǎo)入頭文件

// 創(chuàng)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;
  //設(shè)置代理
  self.homeCollectionView.delegate = self;
  self.homeCollectionView.dataSource = self;
  [self.view addSubview:self.homeCollectionView];

  // 注冊表頭
  [self.homeCollectionView registerClass:[YJHeaderCollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:kCollectionHeaderView];

  // 注冊表尾
  [self.homeCollectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:kCollectionFooterView];

Swift版

喜歡swift 不需要導(dǎo)入頭文件那么麻煩

//
// CustomCollectionViewFlowLayout.swift
// 
//
// Created by GongHui_YJ on 16/8/4.
// Copyright © 2016年YangJian. All rights reserved.
//

import UIKit

class 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
  }

}

在控制器 viewDidLoad方法實(shí)現(xiàn)

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)

  // 注冊表頭表尾
  let headerNib = UINib(nibName: "HeaderCollectionReusableView", bundle: nil)
  self.homeCollectionView.registerNib(headerNib, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: collectionHeaderId)

  self.homeCollectionView.registerClass(UICollectionReusableView.classForCoder(), forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier: collectionFooterId)

注：不要實(shí)現(xiàn)UICollectionViewDelegateFlowLayout的代理方法了。

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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