UICollectionView

创建

#pragma mark -  初始化CollectionView
- (void)settingCollectionView {
    
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    CGFloat kSectionMargin = W(5);
    //每行3个Cell
    CGFloat screenWith = self.view.bounds.size.width;
    CGFloat cellWidth = (screenWith - 4 *kSectionMargin)/3 ;
    //定义每个item 的大小
    flowLayout.itemSize = CGSizeMake(cellWidth, cellWidth*140/118);
    //头部大小
    flowLayout.headerReferenceSize = CGSizeMake(screenWith, SCREEN_WIDTH*288/375);
    //定义每个item 横向的间距
    flowLayout.minimumLineSpacing = kSectionMargin;
    //定义每个item 纵向的间距
    flowLayout.minimumInteritemSpacing = kSectionMargin;
    //定义每个item 的边距距 //上左下右
    flowLayout.sectionInset = UIEdgeInsetsMake(kSectionMargin, kSectionMargin, kSectionMargin, kSectionMargin);
    
    _collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, WIDTH, HEIGHT-64) collectionViewLayout:flowLayout];
    _collectionView.backgroundColor = [UIColor clearColor];
    _collectionView.showsVerticalScrollIndicator = NO;
    _collectionView.showsHorizontalScrollIndicator = NO;
    _collectionView.dataSource = self;
    _collectionView.delegate = self;
    
    [self.view addSubview:self.collectionView];
    [self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:cellID];
    [self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:headerID];

}

代理

#pragma mark- UICollectionViewDelegate\UICollectionViewDataSource

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
    return 1;
}

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
    return self.dataArr.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellID forIndexPath:indexPath];
    [cell.contentView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
    
    dataModel *model = self.dataArr[indexPath.row];
    
    NSString *urlStr;
    if (model.imgUrl.count) {
        urlStr = model.imgUrl[0];
    }
    UIImageView *cellImageV = [[UIImageView alloc] initWithFrame:cell.contentView.bounds];
    [cellImageV sd_setImageWithURL:[NSURL URLWithString:urlStr] placeholderImage:[UIImage imageNamed:@"占位图"]];
    cellImageV.contentMode = UIViewContentModeScaleToFill;
    [cell.contentView addSubview:cellImageV];
    
    return cell;
}

- (void)collectionView:(UICollectionView *)collectionView      didSelectItemAtIndexPath:(NSIndexPath *)indexPath {
    dataModel *model = self.dataArr[indexPath.row];
    DetailsController *vc = [[DetailsController alloc] init];
    vc.hidesBottomBarWhenPushed = YES;
    vc.ClassId = model.findImgDetails_id;
    [self.navigationController pushViewController:vc animated:YES];
    
}

// 头部或者尾部视图
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    if (kind == UICollectionElementKindSectionHeader) {
        UICollectionReusableView *headerRV = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:headerID forIndexPath:indexPath];
        [headerRV.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];

        [headerRV addSubview:_bannerView];
        
        return headerRV;
    }else //尾部视图
    {
        return nil;
    }
}