初始化:
//初始化布局类(UICollectionViewLayout的子类)
UICollectionViewFlowLayout *fl = [[UICollectionViewFlowLayout alloc]init];
//初始化collectionView
self.collectionView = [[UICollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:fl];
//设置代理
self.collectionView.delegate = self;
self.collectionView.dataSource = self;
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需要实现的协议:
UICollectionViewDataSource, UICollectionViewDelegateFlowLayout
PS:UICollectionViewDelegateFlowLayout是UICollectionViewDelegate的子协议
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注册相应的UICollectionViewCell子类到collectionView用来从队列提取和显示
- (void)registerClass:(Class)cellClass forCellWithReuseIdentifier:(NSString *)identifier;
PS:如果是用nib创建的话，使用下面这个函数来注册。
- (void)registerNib:(UINib *)nib forCellWithReuseIdentifier:(NSString *)identifier;
如果需要显示每个section的headerView或footerView，则还需注册相应的UICollectionReusableView的子类到collectionView
elementKind是header或footer的标识符，只有两种可以设置UICollectionElementKindSectionHeader和UICollectionElementKindSectionFooter
- (void)registerClass:(Class)viewClass forSupplementaryViewOfKind:(NSString *)elementKind withReuseIdentifier:(NSString *)identifier;
PS:如果是用nib创建的话，使用下面这个函数来注册。
- (void)registerNib:(UINib *)nib forSupplementaryViewOfKind:(NSString *)kind withReuseIdentifier:(NSString *)identifier;
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实现协议的函数:
跟UITableView的DataSource和Delegate很像，大可自行代入理解。
DataSource:
//每一组有多少个cell
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section;
//定义并返回每个cell
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath;
//collectionView里有多少个组
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView;
//定义并返回每个headerView或footerView
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
上面这个方法使用时必须要注意的一点是，如果布局没有为headerView或footerView设置size的话(默认size为CGSizeZero)，则该方法不会被调用。所以如果需要显示header或footer，需要手动设置size。
可以通过设置UICollectionViewFlowLayout的headerReferenceSize和footerReferenceSize属性来全局控制size。或者通过重载以下代理方法来分别设置
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section;
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section;
Delegate:
//每一个cell的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath;
//设置每组的cell的边界, 具体看下图
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section;
//cell的最小行间距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section;
//cell的最小列间距
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;
//cell被选择时被调用
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath;
//cell反选时被调用(多选时才生效)
- (void)collectionView:(UICollectionView *)collectionView didDeselectItemAtIndexPath:(NSIndexPath *)indexPath;
例子：
- (void)viewDidLoad {
[super viewDidLoad];
self.titleLab.text = @"会员信息";
UICollectionViewFlowLayout *layout = [UICollectionViewFlowLayout new];
layout.headerReferenceSize = CGSizeMake(self.view.bounds.size.width, 50.0f);
_collectionView = [[UICollectionView alloc]initWithFrame:CGRectZero collectionViewLayout:layout];
[_collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];
[self.view addSubview:_collectionView];
[_collectionView mas_makeConstraints:^(MASConstraintMaker *make) {
make.top.equalTo(self.navView.mas_bottom).offset(0);
make.width.equalTo(self.view.mas_width);
make.left.offset(0);
make.bottom.offset(0);
}];
_collectionView.dataSource = self;
_collectionView.delegate = self;
[_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"1"];
}
#pragma mark UICollectionViewDataSource,UICollectionViewDelegate
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
return 10;
}
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
return 3;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"1" forIndexPath:indexPath];
cell.backgroundColor = [UIColor redColor];
return cell;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section;
{
return 20;
}
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section{
return 20;
}
//每一个cell的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
if(indexPath.section == 0){
return CGSizeMake(50, 50);
}else if(indexPath.section == 1){
return CGSizeMake(self.view.bounds.size.width, 100);
}else{
return CGSizeMake(80, 80);
}
}
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
UICollectionReusableView *resableView = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"header" forIndexPath:indexPath];
UILabel *label = (UILabel *)[resableView viewWithTag:100];
if (!label) {
label = [[UILabel alloc] initWithFrame:CGRectMake(0, 5, collectionView.frame.size.width, 40.0f)];
label.backgroundColor = [UIColor colorWithWhite:0.9 alpha:1];
label.textColor = [UIColor blackColor];
label.tag = 100;
[resableView addSubview:label];
}
if (indexPath.section == 0) {
label.text = @"切换栏目";
UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
button.frame = CGRectMake(self.view.bounds
.size.width - 100.0f, 10.0f, 80, 30.0f);
[button setTitle:@"排序删除" forState:UIControlStateNormal];
[button setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
button.layer.borderColor = [UIColor redColor].CGColor;
button.layer.masksToBounds = YES;
button.layer.cornerRadius = 5;
button.layer.borderWidth = 1;
[resableView addSubview:button];
}else{
label.text = @"点击添加更多栏目";
}
return resableView;
}