UICollectionView的使用

文件结构：

一：先定义cell，这里是Cell类，继承自UICollectionViewCell，用xib画出cell

CollectionCell.h

#import <UIKit/UIKit.h>

@interface CollectionCell : UICollectionViewCell

@end

CollectionCell.c

#import "CollectionCell.h"

@implementation CollectionCell

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {
        // 初始化时加载collectionCell.xib文件
        NSArray *arrayOfViews = [[NSBundle mainBundle] loadNibNamed:@"CollectionCell" owner:self options:nil];
        
        // 如果路径不存在，return nil
        if (arrayOfViews.count < 1)
        {
            return nil;
        }
        // 如果xib中view不属于UICollectionViewCell类，return nil
        if (![[arrayOfViews objectAtIndex:0] isKindOfClass:[UICollectionViewCell class]])
        {
            return nil;
        }
        // 加载nib
        self = [arrayOfViews objectAtIndex:0];
    }
    return self;
}

CollectionCell.xib

画出cell：

设置Cell大小：

设置Identifier：

设置Class：

二：UICollectionViewController

1.CollectionViewController.h

#import <UIKit/UIKit.h>
#import "CollectionCell.h"

@interface CollectionViewController : UICollectionViewController


@end

2.CollectionViewController.c

#import "CollectionViewController.h"

@interface CollectionViewController ()

@end

@implementation CollectionViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.

    self.collectionView.dataSource = self;
    self.collectionView.delegate = self;
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
    return 4;
}

-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
    [self.collectionView registerClass:[CollectionCell class] forCellWithReuseIdentifier:@"CollectionCell"];
    
    CollectionCell *cell = (CollectionCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"CollectionCell" forIndexPath:indexPath];
    
    
    return cell;
}

//- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
//{
//    CGFloat width = indexPath.row * 50;
//    CGFloat height = indexPath.row * 50;
//    return CGSizeMake(width,height);
//    
//}

@end

3.CollectionViewController.xib:

结构：

删除原来的view，拖一个collectionView进来

设置file's owner

custom class

cell大小及间隙

outlet：

常见错误：

1.只有collectionView，没有Cell显示出来，那么重写自定义Cell类的 - (id)initWithFrame:(CGRect)frame 方法，从nib加载或者自定义。

2.Xcode运行时报错：

UICollectionElementKindCell with identifier CollectionCell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard

检查有没有注册identifier：在viewDidLoad方法里加入：

[self.collectionView registerClass:[CollectionCell class] forCellWithReuseIdentifier:@"CollectionCell"];

3.

'NSInternalInconsistencyException', reason: '-[UIViewController _loadViewFromNibNamed:bundle:] loaded the "CollectionViewController" nib but the view outlet was not set.

file's owner中的view属性没有设置，连线view属性和xib中的collectionView

3.出现错误：'UICollectionView must be initialized with a non-nil layout parameter'

去xib文件中的collectionView下面的Collection View Flow Layout中的sizeInspector中改变一下Min Spacing或者给在Cell的xib中设置一下Cell的IDentiFier