直接上代码，说明请看注释吧
```
ViewController.h
#import
@interface ViewController : UIViewController{
}
@property (strong, nonatomic)UICollectionView *collectionView;
@end
ViewController.m
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//确定是水平滚动，还是垂直滚动
UICollectionViewFlowLayout *flowLayout=[[UICollectionViewFlowLayout alloc] init];
[flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
self.collectionView=[[UICollectionView alloc] initWithFrame:CGRectMake(0,64,320,200) collectionViewLayout:flowLayout];
self.collectionView.dataSource=self;
self.collectionView.delegate=self;
[self.collectionView setBackgroundColor:[UIColor clearColor]];
//注册Cell，必须要有
[self.collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"UICollectionViewCell"];
[self.view addSubview:self.collectionView];
}
#pragmamark -- UICollectionViewDataSource
//定义展示的UICollectionViewCell的个数
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
return10;
}
//定义展示的Section的个数
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return2;
}
//每个UICollectionView展示的内容
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
static NSString * CellIdentifier =@"UICollectionViewCell";
UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier:CellIdentifier forIndexPath:indexPath];
cell.backgroundColor = [UIColor colorWithRed:((10* indexPath.row) /255.0) green:((20* indexPath.row)/255.0) blue:((30* indexPath.row)/255.0) alpha:1.0f];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0,0,20,20)];
label.textColor = [UIColor redColor];
label.text = [NSString stringWithFormat:@"%d",indexPath.row];
for (id subView in cell.contentView.subviews) {
[subView removeFromSuperview];
}
[cell.contentView addSubview:label];
return cell;
}
#pragmamark --UICollectionViewDelegateFlowLayout
//定义每个Item 的大小
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
return CGSizeMake(60,60);
}
//定义每个UICollectionView 的 margin
-(UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
{
return UIEdgeInsetsMake(5,5,5,5);
}
#pragmamark --UICollectionViewDelegate
//UICollectionView被选中时调用的方法
-(void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell * cell = (UICollectionViewCell *)[collectionView cellForItemAtIndexPath:indexPath];
//临时改变个颜色，看好，只是临时改变的。如果要永久改变，可以先改数据源，然后在cellForItemAtIndexPath中控制。（和UITableView差不多吧！O(∩_∩)O~）
cell.backgroundColor = [UIColor greenColor];
NSLog(@"item======%d",indexPath.item);
NSLog(@"row=======%d",indexPath.row);
NSLog(@"section===%d",indexPath.section);
}
//返回这个UICollectionView是否可以被选择
-(BOOL)collectionView:(UICollectionView *)collectionView shouldSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
return YES;
}
@end
```
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