iOS 使用UICollectionView实现图片轮播

1.因为UICollectionView继承于UIScrollView，所以我们可以使用UICollectionView来实现图片的无限轮播，当图片数量增加UICollectionView可以帮助我们减少内存的消耗。

#import "ViewController.h"static NSString *cellIdef_ = @"cellIdef";@interface ViewController ()<UICollectionViewDataSource,UICollectionViewDelegate>@property (nonatomic,strong) UICollectionView *collectionView;@property (nonatomic,strong) UIPageControl   *pageControl;@property (nonatomic,strong) NSTimer           *timer;- (void)initialUSerInterface;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    self.view.backgroundColor = [UIColor whiteColor];    [self initialUSerInterface];    // Do any additional setup after loading the view, typically from a nib.}//懒加载pageControl- (UIPageControl *)pageControl{    if (_pageControl == nil) {        //分页控件，本质上和scorllView没有任何关系，是2个独立的控件        _pageControl = [[UIPageControl alloc]init];        _pageControl.numberOfPages = 5;        CGSize size = [_pageControl sizeForNumberOfPages:5];        _pageControl.bounds = CGRectMake(0, 0, size.width, size.width);        _pageControl.center = CGPointMake(self.view.center.x, 130);        _pageControl.pageIndicatorTintColor = [UIColor redColor];        [self.view addSubview:_pageControl];    }    return _pageControl;}- (void)initialUSerInterface{    UICollectionViewFlowLayout *layout = [[UICollectionViewFlowLayout alloc]init];    layout.itemSize = CGSizeMake(self.view.frame.size.width, 250);    layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;    UICollectionView *collectionView = [[UICollectionView alloc]initWithFrame:CGRectMake(0, 10, self.view.frame.size.width, 250) collectionViewLayout:layout];    collectionView.backgroundColor = [UIColor whiteColor];    collectionView.delegate = self;    collectionView.dataSource = self;    [collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:cellIdef_];    collectionView.pagingEnabled = YES;    collectionView.showsHorizontalScrollIndicator = NO;    collectionView.showsVerticalScrollIndicator = NO;    collectionView.bounces = NO;    collectionView.contentSize = CGSizeMake(5 * collectionView.bounds.size.width, 0);    [self.view addSubview:collectionView];    self.collectionView = collectionView;    [self addNSTime];    self.pageControl.currentPage = 0;}//添加定时器- (void)addNSTime{    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(nextPage) userInfo:nil repeats:YES];    //添加到runloop中    [[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];    [timer fire];    self.timer = timer;}//删除定时器- (void)removeNSTimer{    [self.timer invalidate];    self.timer = nil;}//自动滚动- (void)nextPage{   NSInteger currentNumber = self.pageControl.currentPage;    CGFloat x = ((currentNumber + 1)%5) * self.collectionView.bounds.size.width;    if (currentNumber <= 5) {        [self.collectionView setContentOffset:CGPointMake(x, 0) animated:YES];    }else{        [self.collectionView setContentOffset:CGPointMake(x, 0) animated:NO];    }        self.pageControl.currentPage = x;}#pragma mark --)<UICollectionViewDataSource,UICollectionViewDelegate>- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView{    return 1;}- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{    return 5;}- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{    UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdef_ forIndexPath:indexPath];    cell.backgroundColor = [UIColor yellowColor];    UIImageView *image = [[UIImageView alloc]initWithImage:[UIImage imageNamed:[NSString stringWithFormat:@"%ld",indexPath.row + 1]]];    image.frame = cell.bounds;    [cell addSubview:image];    return cell;}//当用户开始拖拽的时候就调用- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView{    [self removeNSTimer];}//当用户停止拖拽的时候调用- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{    [self addNSTime];}//设置页码- (void)scrollViewDidScroll:(UIScrollView *)scrollView{    int page = (int)(scrollView.contentOffset.x/scrollView.frame.size.width + 0.5)%5;    self.pageControl.currentPage = page;}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167