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

1 #import <UIKit/UIKit.h>
2 
3 @interface CollectionCell : UICollectionViewCell
4 
5 @end

CollectionCell.c

 1 #import "CollectionCell.h"
 2 
 3 @implementation CollectionCell
 4 
 5 - (id)initWithFrame:(CGRect)frame
 6 {
 7     self = [super initWithFrame:frame];
 8     if (self)
 9     {
10         // 初始化时加载collectionCell.xib文件
11         NSArray *arrayOfViews = [[NSBundle mainBundle] loadNibNamed:@"CollectionCell" owner:self options:nil];
12         
13         // 如果路径不存在，return nil
14         if (arrayOfViews.count < 1)
15         {
16             return nil;
17         }
18         // 如果xib中view不属于UICollectionViewCell类，return nil
19         if (![[arrayOfViews objectAtIndex:0] isKindOfClass:[UICollectionViewCell class]])
20         {
21             return nil;
22         }
23         // 加载nib
24         self = [arrayOfViews objectAtIndex:0];
25     }
26     return self;
27 }

CollectionCell.xib

画出cell：

设置Cell大小：

设置Identifier：

设置Class：

二：UICollectionViewController

1.CollectionViewController.h

1 #import <UIKit/UIKit.h>
2 #import "CollectionCell.h"
3 
4 @interface CollectionViewController : UICollectionViewController
5 
6 
7 @end

2.CollectionViewController.c

 1 #import "CollectionViewController.h"
 2 
 3 @interface CollectionViewController ()
 4 
 5 @end
 6 
 7 @implementation CollectionViewController
 8 
 9 - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
10 {
11     self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
12     if (self) {
13         // Custom initialization
14     }
15     return self;
16 }
17 
18 - (void)viewDidLoad
19 {
20     [super viewDidLoad];
21     // Do any additional setup after loading the view from its nib.
22 
23     self.collectionView.dataSource = self;
24     self.collectionView.delegate = self;
25 }
26 
27 - (void)didReceiveMemoryWarning
28 {
29     [super didReceiveMemoryWarning];
30     // Dispose of any resources that can be recreated.
31 }
32 
33 -(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
34 {
35     return 4;
36 }
37 
38 -(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
39 {
40     [self.collectionView registerClass:[CollectionCell class] forCellWithReuseIdentifier:@"CollectionCell"];
41     
42     CollectionCell *cell = (CollectionCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"CollectionCell" forIndexPath:indexPath];
43     
44     
45     return cell;
46 }
47 
48 //- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath
49 //{
50 //    CGFloat width = indexPath.row * 50;
51 //    CGFloat height = indexPath.row * 50;
52 //    return CGSizeMake(width,height);
53 //    
54 //}
55 
56 @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"];

'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