01.轮播图之三 ： collectionView 轮播

个人觉得 collection view 做轮播是最方便的，设置下flowlayout 其他不会有很大的变动，没有什么逻辑的代码

let's begin……

创建自定义的view

.h 声明文件

@interface CollectionViewShuffling : UIView

@property (nonatomic,strong)NSArray *array;

@end

.m 实现文件

@interface CollectionViewShuffling ()<UICollectionViewDelegate, UICollectionViewDataSource>

@property (nonatomic,strong)UICollectionView *collectionView;
@property (nonatomic,strong)NSMutableArray *collectionArray;

@end

@implementation CollectionViewShuffling
@synthesize array = _array;

-(instancetype)initWithFrame:(CGRect)frame{
    
    if (self == [super initWithFrame:frame]) {
    }
    return self;
}
/**
这个是横向滚动轮播的重点研究对象
*/
-( UICollectionViewFlowLayout *)creatFlowLayout{
    // 创建UICollectionViewFlowLayout约束对象
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    // 设置item的Size大小
    flowLayout.itemSize = CGSizeMake(self.frame.size.width, self.frame.size.height);
    // 设置uicollection 的 横向滑动
    flowLayout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
    flowLayout.minimumLineSpacing = 0;
    return  flowLayout;
}

- (UICollectionView *)collectionView
{
    if (!_collectionView) {
        UICollectionViewFlowLayout *flowLayout = [self creatFlowLayout];
        _collectionView = [[UICollectionView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width,  self.frame.size.height) collectionViewLayout:flowLayout];
        [self addSubview:_collectionView];
        // 设置代理
        _collectionView.delegate = self;
        _collectionView.dataSource = self;
//        _collectionView.showsHorizontalScrollIndicator = NO;// 设置不展示滑动条
        _collectionView.pagingEnabled = YES; // 设置整页滑动
        // 设置当前collectionView 到哪个位置(indexPath row 0 section 取中间(50个))
        
        [_collectionView registerNib:[UINib nibWithNibName:@"ShufflingItem" bundle:nil] forCellWithReuseIdentifier:@"ShufflingItem"];
    }
    return _collectionView;
}

-(void)setArray:(NSArray *)array{
    NSAssert(array.count != 0, @"传入的滚动数组是 空的");
    _array = array;
    [self prepareData];
    [self prepareUI];
}

-(void)prepareUI{
    
    [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:1 inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:false];
    [self.collectionView reloadData];
}

- (void)prepareData{
    
    self.collectionArray = [NSMutableArray new];
    //    首位 添加数组最后的元素
    [self.collectionArray addObject:_array.lastObject];
    //   添加数组元素
    [self.collectionArray addObjectsFromArray:_array];
    //    末尾 补充第一个元素
    [self.collectionArray addObject:_array.firstObject];
}
/*
 collection view  delegate
 */
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 1;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return self.collectionArray.count;
}

- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    ShufflingItem *item = [collectionView dequeueReusableCellWithReuseIdentifier:@"ShufflingItem" forIndexPath:indexPath];
    if (!item) {
        item = [[ShufflingItem alloc] init];
    }
    item.imageView.backgroundColor = self.collectionArray[indexPath.row];
    return item;
}


-(void)scrollViewDidScroll:(UIScrollView *)scrollView{

    if (scrollView == self.collectionView) {
        
        NSLog(@"scroll content %@",NSStringFromCGPoint(scrollView.contentOffset));
        
        //检测移动的位移
        if (scrollView.contentOffset.x == (self.collectionArray.count-1)*(self.frame.size.width) ) {
            
            [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:1 inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:false];

        }else if (scrollView.contentOffset.x == 0){
            
            [self.collectionView scrollToItemAtIndexPath:[NSIndexPath indexPathForItem:(self.collectionArray.count-2) inSection:0] atScrollPosition:UICollectionViewScrollPositionLeft animated:false];
        }else{
            
            //            正常滚动
        }
    }
}

 最简单的collection 轮播，实现啦……

总结下，他的实现为什么如此简单

1. collection view 有个flow layout 设置这个属性就可以让他横向滚动，竖向滚动
2. 还有一个重点 声明下 collection view 使用 item cell 的时候，是必须注册的

调用方法：：：：

-(void)prepareCollectShuffling{
    
    CollectionViewShuffling *collectShuffling = [[CollectionViewShuffling alloc]initWithFrame:CGRectMake(10, 320, self.view.frame.size.width -20, 220)];
    [self.view addSubview:collectShuffling];;
    collectShuffling.array = self.arr;
}

这个写完，距离成功又进了一步，继续………………