1 //
  2 //  ViewController.m
  3 //  HeaderCollectionView
  4 //
  5 //  Created by 思 彭 on 16/10/24.
  6 //  Copyright © 2016年 思 彭. All rights reserved.
  7 //
  8
  9 #import "ViewController.h"
 10 #import "SectionHeaderView.h"
 11
 12 @interface ViewController ()<UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout>
 13
 14 @property (nonatomic, strong) UICollectionView *collectionView;
 15
 16 @end
 17
 18 @implementation ViewController
 19
 20 #pragma mark - life Cycle
 21
 22 - (void)viewDidLoad {
 23     [super viewDidLoad];
 24     self.title = @"HeaderCollectionView";
 25     self.automaticallyAdjustsScrollViewInsets = NO;
 26     self.navigationController.navigationBar.translucent = NO;
 27     self.view.backgroundColor = [UIColor whiteColor];
 28     [self setCollectionView];
 29     [self setHeaderView];
 30 }
 31
 32 #pragma mark - setUI
 33
 34 - (void)setCollectionView {
 35
 36     UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];
 37     layout.itemSize = CGSizeMake((self.view.frame.size.width - 30) / 3, (self.view.frame.size.width - 30) / 3);
 38     self.collectionView = [[UICollectionView alloc]initWithFrame:self.view.bounds collectionViewLayout:layout];
 39     self.collectionView.backgroundColor = [UIColor clearColor];
 40     self.collectionView.delegate = self;
 41     self.collectionView.dataSource = self;
 42     // 最重要的一句代码!!!
 43     self.collectionView.contentInset = UIEdgeInsetsMake(200, 0, 0, 0);
 44     self.collectionView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
 45     [self.view addSubview:self.collectionView];
 46
 47     // 注册cell
 48     [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"collectionCellIdentify"];
 49     [self.collectionView registerNib:[UINib nibWithNibName:@"SectionHeaderView" bundle:nil] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"sectionHeaderView"];
 50 }
 51
 52 - (void)setHeaderView {
 53
 54     // 注意这里设置headerView的头视图的y坐标一定是从"负值"开始,因为headerView是添加在collectionView上的.
 55     UIView *headerView = [[UIView alloc]initWithFrame:CGRectMake(0, -200, self.view.frame.size.width, 200)];
 56     headerView.backgroundColor = [UIColor greenColor];
 57     [self.collectionView addSubview:headerView];
 58 }
 59
 60 #pragma mark - UICollectionViewDataSource
 61
 62 - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
 63
 64     return 10;
 65 }
 66
 67 - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
 68
 69     return 5;
 70 }
 71
 72 - (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
 73
 74     UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"collectionCellIdentify" forIndexPath:indexPath];
 75     cell.backgroundColor = [UIColor redColor];
 76     return cell;
 77 }
 78
 79 #pragma mark - UICollectionViewDelegateFlowLayout
 80
 81 - (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section {
 82
 83     return UIEdgeInsetsMake(0, 0, 0, 0);
 84 }
 85
 86 #pragma mark - UICollectionViewDelegate
 87
 88 - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
 89
 90     // 复用SectionHeaderView,SectionHeaderView是xib创建的
 91     SectionHeaderView *headerView = [self.collectionView dequeueReusableSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"sectionHeaderView" forIndexPath:indexPath];
 92     return headerView;
 93
 94 }
 95
 96 - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section {
 97
 98     return CGSizeMake(self.view.frame.size.width, 41);
 99 }
100
101 @end