UICollectionView 简单使用

#import "ViewController.h"

#define _CELL @ "acell"

@interface ViewController ()< UICollectionViewDataSource , UICollectionViewDelegate , UICollectionViewDelegateFlowLayout >

@property (nonatomic , strong) UICollectionView * collectionView;
@property (nonatomic , strong) NSMutableArray *arr;
@property (nonatomic , assign) CGFloat Height;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self arr];
    [self collectionView];
}

#pragma mark - lazyload

-(UICollectionView *)collectionView{
    if (_collectionView == nil) {
        NSInteger i = _arr.count-1;
        _Height       = 20+(i/4+1)*20+(i/4)*10;
        //先实例化一个层
        UICollectionViewFlowLayout *layout=[[ UICollectionViewFlowLayout alloc ] init ];
        [layout setScrollDirection:UICollectionViewScrollDirectionVertical];
        
        //创建UICollectionView大小
        _collectionView=[[ UICollectionView alloc ] initWithFrame:CGRectMake(0, 64, self.view.frame.size.width, _Height) collectionViewLayout :layout];
        //注册Cell类
        [_collectionView registerClass :[ UICollectionViewCell class ] forCellWithReuseIdentifier : _CELL ];
        _collectionView. delegate = self ;
        _collectionView. dataSource = self ;
        _collectionView.backgroundColor = [UIColor grayColor];
        [ self . view addSubview :_collectionView];
    }
    return _collectionView;
}

-(NSMutableArray *)arr{
    if (_arr==nil) {
        _arr =  [[NSMutableArray alloc]initWithObjects:@"父母之魂1",@"父母之魂2",@"父母之魂3",@"父母之魂4",@"父母之魂5",@"父母之魂6",@"父母之魂7",@"父母之魂8",@"父母之魂1",@"父母之魂2",@"父母之魂3",@"父母之魂4",@"父母之魂5",@"父母之魂6",@"父母之魂7",@"父母之魂8",nil];
    }
    return _arr;
}

#pragma mark --UICollectionViewDataSource

//定义展示的UICollectionViewCell的个数
-( NSInteger )collectionView:( UICollectionView *)collectionView numberOfItemsInSection:( NSInteger )section{
    return _arr.count ;
}

//定义展示的Section的个数
-( NSInteger )numberOfSectionsInCollectionView:( UICollectionView *)collectionView{
    return 1 ;
}

//每个UICollectionView展示的内容
-( UICollectionViewCell *)collectionView:( UICollectionView *)collectionView cellForItemAtIndexPath:( NSIndexPath *)indexPath{
    UICollectionViewCell * cell = [collectionView dequeueReusableCellWithReuseIdentifier : _CELL forIndexPath :indexPath];
    
    UIButton * btn = [[UIButton alloc]initWithFrame:CGRectMake(0, 0, 70, 20)];
    [btn setTitleColor:[UIColor blackColor] forState:(UIControlStateNormal)];
    btn.backgroundColor = [UIColor yellowColor];
    [btn setTitle:[_arr objectAtIndex:indexPath.row]  forState:(UIControlStateNormal)];
    [cell.contentView addSubview:btn];
    btn.userInteractionEnabled = NO;
    
    return cell;
}

#pragma mark --UICollectionViewDelegate

//UICollectionView被选中时调用的方法
-( void )collectionView:( UICollectionView *)collectionView didSelectItemAtIndexPath:( NSIndexPath *)indexPath{
    NSLog(@"%ld",(long)indexPath.row);
    [_arr removeObjectAtIndex:indexPath.row];
    [collectionView deleteItemsAtIndexPaths:[NSArray arrayWithObject:indexPath]];
    //删除后再计算collection的高度
    NSInteger i = _arr.count-1;
    _Height       = 20+(i/4+1)*20+(i/4)*10;
    _collectionView.frame = CGRectMake(0, 64, self.view.frame.size.width, _Height);
}

//返回这个UICollectionViewCell是否可以被选择
-( BOOL )collectionView:( UICollectionView *)collectionView shouldSelectItemAtIndexPath:( NSIndexPath *)indexPath{
    return YES ;
}

#pragma mark --UICollectionViewDelegateFlowLayout
//定义每个UICollectionView 的大小
- ( CGSize )collectionView:( UICollectionView *)collectionView layout:( UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:( NSIndexPath *)indexPath{
    return CGSizeMake ( 70 , 20 );
}

//定义每个UICollectionView 的边距(次序: 上，左，下，右边)
-( UIEdgeInsets )collectionView:( UICollectionView *)collectionView layout:( UICollectionViewLayout *)collectionViewLayout insetForSectionAtIndex:( NSInteger )section{
    return UIEdgeInsetsMake ( 10 , 10 , 10 , 10 );
}

//设置单元格间的横向间距
- (CGFloat) collectionView:(UICollectionView *)collectionView
                    layout:(UICollectionViewLayout *)collectionViewLayout
minimumInteritemSpacingForSectionAtIndex:(NSInteger)section{
    return (self.view.frame.size.width-10-280)/4;
}

//设置单元格间的竖向间距
- (CGFloat) collectionView:(UICollectionView *)collectionView
                    layout:(UICollectionViewLayout *)collectionViewLayout
minimumLineSpacingForSectionAtIndex:(NSInteger)section
{
    return 10;
}

// 长按某item，弹出copy和paste的菜单
- (BOOL)collectionView:(UICollectionView *)collectionView shouldShowMenuForItemAtIndexPath:(NSIndexPath *)indexPath
{
    return YES;
}

// 使copy和paste有效
- (BOOL)collectionView:(UICollectionView *)collectionView canPerformAction:(SEL)action forItemAtIndexPath:(NSIndexPath *)indexPath withSender:(nullable id)sender
{
    if ([NSStringFromSelector(action) isEqualToString:@"copy:"] || [NSStringFromSelector(action) isEqualToString:@"paste:"])
    {
        return YES;
    }
    
    return NO;
}

- (void)collectionView:(UICollectionView *)collectionView performAction:(SEL)action forItemAtIndexPath:(NSIndexPath *)indexPath withSender:(nullable id)sender
{
    if([NSStringFromSelector(action) isEqualToString:@"copy:"])
    {
        NSLog(@"-------------执行拷贝-------------");
        //点击长按弹出copy和paste--点击copy删除cell
        __weak typeof(self)weakSelf = self;
        [_collectionView performBatchUpdates:^{
            [weakSelf.arr removeObjectAtIndex:indexPath.row];
            [weakSelf.collectionView deleteItemsAtIndexPaths:@[indexPath]];
            //删除后再计算collection的高度
            NSInteger i = weakSelf.arr.count-1;
            weakSelf.Height       = 20+(i/4+1)*20+(i/4)*10;
            weakSelf.collectionView.frame = CGRectMake(0, 64, self.view.frame.size.width, weakSelf.Height);
            
        } completion:nil];
    }
    else if([NSStringFromSelector(action) isEqualToString:@"paste:"])
    {
        NSLog(@"-------------执行粘贴-------------");
        //点击长按弹出copy和paste--点击paste添加一个cell
        __weak typeof(self)weakSelf = self;
        [_collectionView performBatchUpdates:^{
            // 构造一个indexPath
            NSIndexPath *indePath = [NSIndexPath indexPathForItem:weakSelf.arr.count inSection:0];
            [weakSelf.collectionView insertItemsAtIndexPaths:@[indePath]]; // 然后在此indexPath处插入给collectionView插入一个item
            [weakSelf.arr addObject:@"x"]; // 保持collectionView的item和数据源一致
            //增加后再计算collection的高度
            NSInteger i = weakSelf.arr.count-1;
            weakSelf.Height       = 20+(i/4+1)*20+(i/4)*10;
            weakSelf.collectionView.frame = CGRectMake(0, 64, self.view.frame.size.width, weakSelf.Height);
            
        } completion:nil];
    }
}

@end