UICollectionView

UICollectionView和UITableView十分相似

一般须遵守协议

 < UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout > 

 1. 基本使用

(1)先创建, 创建的时候先创建FlowLayout，然后创建UICollectionView的时候设置layout

//创建Layout, 创建UICollectionView会使用
    UICollectionViewFlowLayout *flowLayout= [[UICollectionViewFlowLayout alloc]init];
    
    //创建
    self.myCollectionView = [[UICollectionView alloc] initWithFrame:self.view.bounds collectionViewLayout:flowLayout];
     self.myCollectionView.delegate = self;
     self.myCollectionView.dataSource = self;
     [self.view addSubview:self.myCollectionView];
    
    //注册cell, 必须加此句提前注册cell, 否则崩溃
    [self.myCollectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"myCell"];

（2）代理方法

#pragma mark - dataSource 代理方法
//此方法可以不写, 默认为1
-(NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 2;
}
//指定section中item的个数
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 10;
}
// The cell that is returned must be retrieved from a call to -dequeueReusableCellWithReuseIdentifier:forIndexPath:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"myCell" forIndexPath:indexPath];
    if(indexPath.section==0)
    {
        cell.backgroundColor = [UIColor redColor];
    }
    if(indexPath.section==1)
    {
        cell.backgroundColor = [UIColor greenColor];
    }
    return cell;
}

(3)FlowLayout 属性和设置

    flowLayout.scrollDirection = UICollectionViewScrollDirectionVertical;//滚动方向
    flowLayout.minimumLineSpacing = 10.0;//行间距(最小值)
    flowLayout.minimumInteritemSpacing = 10;//item间距(最小值)
    flowLayout.itemSize = CGSizeMake(50, 50);//item的大小
    flowLayout.sectionInset = UIEdgeInsetsMake(10, 10, 10, 10);//设置section的边距

cell核心代码

-(id)initWithFrame:(CGRect)frame
{
    if(self = [super initWithFrame:frame])
    {
        //创建ui
        _imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height)];
        [self.contentView addSubview:_imageView];
    }
    return self;
}

 UICollectionView使用基本代码

#import "ViewController.h"

//使用集合视图


@interface ViewController ()<UICollectionViewDataSource,UICollectionViewDelegate,UICollectionViewDelegateFlowLayout>
@property (strong,nonatomic) UICollectionView *collectionView;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    [self createCollectionView];
    
}
-(void)createCollectionView
{
    
    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc] init];
    
    //item 行间距
    flowLayout.minimumLineSpacing = 40;     //默认10
    flowLayout.minimumInteritemSpacing = 20;    //默认10
    //设置统一的item大小
    flowLayout.itemSize = CGSizeMake(50, 50);   //默认50,50
    flowLayout.scrollDirection = UICollectionViewScrollDirectionVertical; //默认竖直滚动
    flowLayout.sectionInset = UIEdgeInsetsMake(10, 10, 10, 10);
    
    
    //创建集合视图
    //参数1: 位置
    //参数2: 传入布局对象, 集合视图item布局由布局对象控制
    _collectionView = [[UICollectionView alloc] initWithFrame:self.view.bounds collectionViewLayout:flowLayout];
    _collectionView.dataSource = self;
    _collectionView.delegate = self;
    [self.view addSubview:_collectionView];
    
    //注册cell
    [_collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"cell"];
}

- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
    return 2;
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 20;
}
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"cell" forIndexPath:indexPath];
    
    if(indexPath.section == 0)
    {
        cell.backgroundColor = [UIColor redColor];
    }
    else
    {
        cell.backgroundColor = [UIColor greenColor];
    }
    
    return cell;
}

-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
{
    double w = 20 + arc4random()%40;
    double h = 20 + arc4random()%40;
    return CGSizeMake(w, h);
}

UICollectionViewLayout自定义布局

//重写方法，准备布局，添加初始化操作

- (void)prepareLayout
{
    [super prepareLayout];
    .......
}

//返回内容的大小，一般返回集合视图大小

- (CGSize)collectionViewContentSize
{
    return self.collectionView.frame.size;
}

//返回所有的item对应布局对象的数组

- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect

//传入item的位置，返回这个item的布局对象

- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath

    圆形布局自定义

#import <UIKit/UIKit.h>
//圆形布局
@interface MyCircleLayout : UICollectionViewLayout
@property (nonatomic)CGPoint center;
@property (nonatomic)CGFloat radius;
@property (nonatomic)CGSize itemSize;
@end

============================================
#import "MyCircleLayout.h"
@interface MyCircleLayout ()
@property (nonatomic)NSInteger cellCount;
@end
@implementation MyCircleLayout

//重写方法，准备布局，添加初始化操作
- (void)prepareLayout
{
    [super prepareLayout];
    
    CGSize size = self.collectionView.frame.size;
    //center
    if (CGPointEqualToPoint(self.center, CGPointZero)) {
        self.center = CGPointMake(size.width/2, size.height/2);
    }
    if (self.radius == 0) {
        self.radius = MIN(size.width/2, size.height/2)*0.8;
    }
    if (CGSizeEqualToSize(self.itemSize, CGSizeZero)) {
        self.itemSize = CGSizeMake(50, 50);
    }
    
    
    //利用集合视图的dataSourse协议
    self.cellCount = [self.collectionView numberOfItemsInSection:0];
}
//返回内容的大小，一般返回集合视图大小
- (CGSize)collectionViewContentSize
{
    return self.collectionView.frame.size;
}
//返回所有的item对应布局对象的数组
- (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect
{
    NSMutableArray *marr = [[NSMutableArray alloc] init];
    for (int i = 0; i < self.cellCount; i ++) {
        NSIndexPath *indexPath = [NSIndexPath indexPathForItem:i inSection:0];
        [marr addObject:[self layoutAttributesForItemAtIndexPath:indexPath]];
    }
    return marr;
}
//传入item的位置，返回这个item的布局对象
- (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath
{
    UICollectionViewLayoutAttributes *attr = [UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];
    //每个item可能有不同的大小，不同的位置
    attr.size = self.itemSize;
    
    //获取角度
    double angle = M_PI*2*indexPath.item / self.cellCount;
    attr.center = CGPointMake(self.center.x+self.radius*cosf(angle), self.center.y+self.radius*sinf(angle));
    
    return attr;
}

@end