UICollectionView-简单讲解

• 好久没有用到UICollectionView差点就不会用了，看来写过的代码要及时复习啊

• 下面贴一下关于UICollectionView的简单用法

• 协议
  //代理、数据源协议 @interface RootViewController ()<UICollectionViewDataSource, UICollectionViewDelegateFlowLayout, UIAlertViewDelegate>

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    //创建数据源
    _dataArray = [[NSMutableArray alloc]initWithCapacity:0];
    for (int i = 0; i < 16; i ++) {
        [_dataArray addObject:[NSString stringWithFormat:@"%d",i+1]];
    }
    
    /************UICollectionView*************/
    //UICollectionView  可以自动布局
    //自动布局的类：UICollectionViewLayout  父类
    //UICollectionViewFlowLayout  网格类控件的自动布局的类
    
    //UICollectionViewFlowLayout 实例化
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc]init];
    //设置UICollectionView的滑动方向
    /*
     1、UICollectionViewScrollDirectionHorizontal  水平滑动
     2、UICollectionViewScrollDirectionVertical  竖直滑动
     */
    //flowLayout.scrollDirection = UICollectionViewScrollDirectionVertical;
    flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    //设置水平方向的空隙
    flowLayout.minimumInteritemSpacing = 20;
    //设置垂直方向的空隙
    flowLayout.minimumLineSpacing = 50;
    //120 + 20  +120 +20  180-120  60
    
    //UICollectionView  的实例化
    UICollectionView *collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 20, self.view.frame.size.width, self.view.frame.size.height - 20) collectionViewLayout:flowLayout];
    //UICollectionViewDelegateFlowLayout  代理
    collectionView.delegate = self;
    //UICollectionViewDataSource   数据源协议
    collectionView.dataSource = self;
    //默认颜色黑色
    collectionView.backgroundColor = [UIColor whiteColor];
    collectionView.tag = 10000;
    [self.view addSubview:collectionView];
    
    //注册cell类
    [collectionView registerClass:[MyCollectionViewCell class] forCellWithReuseIdentifier:@"iden"];
    //注册标题头
    //UICollectionElementKindSectionHeader  标题头
    /*
     supplementary [,sʌplɪ'ment(ə)rɪ]
     
     基本释义
     
     adj. 补充的；追加的
*/
    [collectionView registerClass:[MyCollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"view"];
    //注册标题尾
    //UICollectionElementKindSectionFooter  标题尾
    [collectionView registerClass:[MyCollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionFooter withReuseIdentifier:@"view"];
    
    //刷新数据
    [collectionView reloadData];
    NSLog(@"屏幕的高---->%f",[UIScreen mainScreen].bounds.size.height);
    
}
#pragma mark - UICollectionViewDataSource,UICollectionViewDelegateFlowLayout
//设置段数
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{
    return 1;
}
//设置单元格个数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return _dataArray.count;
}
//UICollectionViewCell
//只能用注册自定义cell的方式
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{

    MyCollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"iden" forIndexPath:indexPath];
    cell.imageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"10_%ld.jpg",(long)indexPath.item]];
    //NSLog(@"%ld",(long)indexPath.item);
//    indexPath.section;  找到某一段
//    indexPath.row == indexPath.item;  找到某一个单元格
    cell.titleLabel.text = _dataArray[indexPath.item];
    return cell;
}

//水平滑动时：最左上角  最左下角
//竖直滑动时：最左上角  最右上角

//设置item的大小
//item的默认大小：50*50
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath{
    //第一个参数：设置item的宽
    //第二个参数：设置item的高
    return CGSizeMake(100, 120);
}
//120 + 100 +120 +100  - 460    20
//设置水平间隙  ： 默认10
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumInteritemSpacingForSectionAtIndex:(NSInteger)section{
    return 50;
}
//设置竖直间隙  ： 默认10
- (CGFloat)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout minimumLineSpacingForSectionAtIndex:(NSInteger)section{
    return 50;
}
//设置边距
- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:(NSInteger)section{
    //上左下右
    return UIEdgeInsetsMake(10 ,10, 10, 10);
}
//点击方法
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
    //
    NSLog(@"%ld====%ld",(long)indexPath.section,(long)indexPath.item);
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"提示" message:@"是否删除" delegate:self cancelButtonTitle:@"确定" otherButtonTitles:@"取消", nil];
    alert.tag = indexPath.item + 1000;
    [alert show];
}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex{
    NSLog(@"%ld",(long)buttonIndex);
    if (buttonIndex==0) {
        [_dataArray removeObjectAtIndex:alertView.tag - 1000];
        UICollectionView *col = (UICollectionView *)[self.view viewWithTag:10000];
        //刷新数据
        [col reloadData];
    }
}
//设置标题头的高度
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForHeaderInSection:(NSInteger)section{
    //水平滑动时：第一个参数有效
    //竖直滑动时：第二个参数有效
    return CGSizeMake(50, 50);
}
//设置标题尾的高度
- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout referenceSizeForFooterInSection:(NSInteger)section{
    //水平滑动时：第一个参数有效
    //竖直滑动时：第二个参数有效
    return CGSizeMake(50, 50);
}
//自定义标题头或标题尾
//需要自定义，需要注册
- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath{
    MyCollectionReusableView *view = [collectionView dequeueReusableSupplementaryViewOfKind:kind withReuseIdentifier:@"view" forIndexPath:indexPath];
    //标题头
    if (kind == UICollectionElementKindSectionHeader) {
        view.label.text = [NSString stringWithFormat:@"第%d标题头",indexPath.section];
    }else if (kind == UICollectionElementKindSectionFooter){
        //标题尾
        view.label.text = [NSString stringWithFormat:@"第%d标题尾",indexPath.section];
    }
    return view;
}

• 这是item cell

#import "MyCollectionViewCell.h"

@implementation MyCollectionViewCell

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        //
        [self creatUI];
    }
    return self;
}
- (void)creatUI{
    _imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height)];
    [self.contentView addSubview:_imageView];
    
    _titleLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, self.bounds.size.height+10, self.bounds.size.width, 20)];
    _titleLabel.backgroundColor = [UIColor clearColor];
    _titleLabel.textColor = [UIColor redColor];
    _titleLabel.textAlignment = NSTextAlignmentCenter;
    _titleLabel.font = [UIFont systemFontOfSize:16.0];
    [self.contentView addSubview:_titleLabel];
}

@end

• 这是 标题头 cell

#import "MyCollectionReusableView.h"

@implementation MyCollectionReusableView

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        //
        [self creatUI];
    }
    return self;
}
- (void)creatUI{
    _label = [[UILabel alloc]initWithFrame:CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height)];
    _label.backgroundColor = [UIColor yellowColor];
    _label.textAlignment = NSTextAlignmentCenter;
    _label.font = [UIFont systemFontOfSize:12.0];
    _label.textColor = [UIColor redColor];
    [self addSubview:_label];
}

@end