UICollectionView 集合视图详解

   UICollectionView 和 UICollectionViewController 类是iOS6 新引进的API，用于展示集合视图，布局更加灵活，可实现多列布局，用法类似于UITableView 和 UITableViewController 类.

- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
//self.view.backgroundColor = [UIColor redColor];

UICollectionViewFlowLayout * layout = [[UICollectionViewFlowLayout alloc]init];
// 设置滚动方向
layout.scrollDirection = UICollectionViewScrollDirectionVertical;
// 设置layout块的大小,决定cell的大小
//layout.itemSize = CGSizeMake(100, 100);
//layout.minimumLineSpacing = 100;
//layout.minimumInteritemSpacing = 100;
//layout.headerReferenceSize = CGSizeMake(320, 40);
//layout.footerReferenceSize = CGSizeMake(320, 80);
//layout.sectionInset = UIEdgeInsetsMake(20, 20, 20, 20);

UICollectionView * collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 20, ScreenWidth, ScreenHeight-20) collectionViewLayout:layout];
collectionView.delegate = self;
collectionView.dataSource = self;
// 注册cell的类型,才能实现cell重用
[collectionView registerClass:[HMTMyCustomCollectionCell class] forCellWithReuseIdentifier:@"cell"];

[self.view addSubview:collectionView];

}

//  设置分区
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{

return 2;

}

//  定义每个分区上的元素个数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{

return 10;

}

//  设置元素内容
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

static NSString * cellIdentifier = @"cell";
HMTMyCustomCollectionCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];

cell.backgroundColor = [UIColor cyanColor];
cell.showLabel.text = [NSString stringWithFormat:@"%ld,%ld",indexPath.section,indexPath.row];

return cell;
}

//  设置每个元素大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{

//    if (indexPath.row % 2 == 0) {
//
//        return CGSizeMake(100, 100);
//    } else {
//
//        return CGSizeMake(50, 150);
//    }
return CGSizeMake(100, 50);

}

//  定义每个元素的margin(边缘 上-左-下-右)
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{

return UIEdgeInsetsMake(0, 0, 0, 0);

}

//  定义单元格所在行line之间的距离,前一行和后一行的距离
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section{

return 20;
}

//  定义每个单元格相互之间的距离
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section{

return 0;

}

//  设置页眉(水平滑动的时候设置width,垂直滑动的时候设置height)
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section{

return CGSizeMake(10, 100);

}

//  设置页脚(水平滑动的时候设置width,垂直滑动的时候设置height)
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section{

return CGSizeMake(10, 10);

}

//  点击元素响应方法
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{

}

/*******************************************自定义Cell***************************************************************/
- (void)createShowLabel{

_showLabel = [[UILabel alloc]initWithFrame:CGRectMake(10, 10, self.bounds.size.width-20, self.bounds.size.height-20)];
_showLabel.backgroundColor = [UIColor redColor];
[self.contentView addSubview:_showLabel];
[_showLabel release];

}

//  重点:防止cell错乱
- (void)layoutSubviews{

[super layoutSubviews];
_showLabel.frame = CGRectMake(10, 10, self.bounds.size.width-20, self.bounds.size.height-20);

}

@附加:可能最不好理解的就是那个上-左-下-右了,给出2张图作参考