对UICollectionView的学习

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

与UICollectionView有关的三个协议:UICollectionViewDataSource,UICollectionViewDelegate,UICollectionViewDelegateFlowLayout

几个常用到得方法(需遵守协议)

- (void)viewDidLoad
{
    [super viewDidLoad];
    //创建一个布局方式
    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc] init];
//    layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    layout.headerReferenceSize = CGSizeMake(320, 50);//header的size
    layout.footerReferenceSize = CGSizeMake(320, 20);
    layout.sectionInset = UIEdgeInsetsMake(0, 0, 20, 0);
    //创建一个集合视图
    UICollectionView *collectionView = [[UICollectionView alloc] initWithFrame:[UIScreen mainScreen].bounds collectionViewLayout:layout];
    collectionView.dataSource = self;
    collectionView.delegate = self;
    [collectionView registerClass:[CustomCell class] forCellWithReuseIdentifier:@"cell"];
    //注册header
    [collectionView registerClass:[CustomHeaderView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];
    //注册footer 增补视图
    [collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"footer"];
    
    [self.view addSubview:collectionView];
    [layout release];
    [collectionView release];
    // Do any additional setup after loading the view.
}
//定义展示的Section的个数
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 2;
}
//定义展示的UICollectionViewCell的个数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 10;
}

//每个UICollectionViewCell展示的内容
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *identifier = @"cell";
    CustomCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
    cell.titleLabel.text = [NSString stringWithFormat:@"%d",indexPath.row];
    cell.backgroundColor = [UIColor orangeColor];
    return cell;
}
//定义每个UICollectionView 中cell的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return CGSizeMake(100, 200);
}
//增补视图header与footer
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
{
    if (kind == UICollectionElementKindSectionHeader) {
        CustomHeaderView *view = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"header" forIndexPath:indexPath];
        view.backgroundColor = [UIColor greenColor];
        return view;
    }else
    {
        UICollectionReusableView *view = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"footer" forIndexPath:indexPath];
        view.backgroundColor = [UIColor redColor];
        return view;
    }
    
}