循环广告我们在开发中已经是熟得不能再熟了，今天整理这篇scrollview三屏复用广告
原理使用scrollview里的三个imageview分别去加载不同的图片，用少量的资源来显示大量或不确定的广告数量，不然如果用普通方法实现广告，难道10个广告用12个scrollview的contentsize去做，岂不是太浪费资源了
代码如下，实现所有数量的循环广告，当广告只有一个时，仅采用单图显示，>=2个广告时，自动采用三屏复用
这里添加图片的方式是通过网络请求，更新服务器上的广告，如果仅使用本地广告，可以将.m文件里的全部图片的添加方式
如：
self.endImageView.image = self.imageArray[endImageCount];
修改为
self.endImageView.image = [UIImage imageNamed:self.imageArray[endImageCount]];
然后在使用该类时，直接将本地图片的名字用数组传过去就行了，如
cview.imageArray = [[NSMutableArray alloc]initWithObjects:@"图片1",@"图片2",@"图片3", nil];
或者不改则使用方法如
NSArray *imageArr = [[NSArray alloc]initWithObjects:@"banner_理财.jpg",@"banner_惠普",@"banner_炒股", nil];
for (int i=0; i<3; i++) {
UIImage *cirImage1 = [UIImage imageNamed:imageArr[i]];
[cirScrollView.imageArray addObject:cirImage1];
}
如果图片给的是地址那可以用imageWithURL这个方法来获取图片
下面讲从服务器获取的广告方式，请求服务器图片及解析这里就不讲了，仅从获取到的data数据后开始
先新建一个类继承UIView，
.h里
1 #import <UIKit/UIKit.h>
2
3 @interface CirculateScrollview : UIView
4
5 @property (nonatomic,strong)NSMutableArray *imageArray;//图片数组
6 @property (nonatomic,strong)UIScrollView *circulateScrollView;//广告
7
8 /*
9 三屏复用广告
10 适用范围:网络请求或固定本地的广告图片
11 适用所有数量广告，广告>=2时自动采用三屏复用技术
12 使用方法:例
13 在需要添加广告的控制器里面
14
15 CirculateScrollview *cview = [[CirculateScrollview alloc]initWithFrame:CGRectMake(0, 20, 320, 200)];
16 for (int i=0; i<3; i++) {
17 UIImage *image = [UIImage imageNamed:@"旅行图1"];//传进图片名字方式
18 //UIImage *image = UIImage imageWithData:data];//传进data数据图片方式将服务器请求到的data数据图片转换成image形式再传输
19 [cview.imageArray addObject:image];
20 }
21 [self.view addSubview:cview];
22
23 */
24
25
26 /*
27 图片转换NSData方法
28 测试可用
29 NSData * data = UIImageJPEGRepresentation(image, 1);
30 */
31
32 @end
.m文件里
实现方法是这三个成员变量，用来读取传输过来的图片在数组中的位置，三屏复用里，我们显示的位置是scrollview的中间位置，左边广告是全部广告的最后一个，中间显示第一个，右边的显示第二个，然后根据左滑成员变量递增，当变量递增到超过广告总数时，重新赋值第一个广告，而右滑递减，递减至－1时，即不在数组范围时，重新赋值广告数组的最后一个
1 #import "CirculateScrollview.h"
2
3 #define ViewWidth self.frame.size.width
4 #define ViewHeight self.frame.size.height
5 #define AllImageCount self.imageArray.count-1
6
7 @interface CirculateScrollview()<UIScrollViewDelegate>
8 {
9 NSInteger endImageCount;//左边图片
10 NSInteger oneImageCount;//中间图片[当前看到的图片]
11 NSInteger secondImageCount;//右边图片
12 }
13 @property (nonatomic,strong)UIImageView *endImageView;
14 @property (nonatomic,strong)UIImageView *oneImageView;
15 @property (nonatomic,strong)UIImageView *secondImageView;
16 @property (nonatomic,strong)UIPageControl *pageCtl;
17
18 @end
19
20 @implementation CirculateScrollview
21
22
23 -(id)initWithFrame:(CGRect)frame
24 {
25 self = [super initWithFrame:frame];
26 if (self) {
27
28 }
29 return self;
30 }
31
32 -(NSMutableArray *)imageArray
33 {
34 if (!_imageArray) {
35 _imageArray = [[NSMutableArray alloc]init];
36 }
37 return _imageArray;
38 }
39
40 - (void)drawRect:(CGRect)rect {
41 self.circulateScrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 0, ViewWidth, ViewHeight)];
42
43 endImageCount = self.imageArray.count-1;
44 oneImageCount = 0;
45 secondImageCount = 1;
46
47 self.circulateScrollView.showsHorizontalScrollIndicator = NO;
48 self.circulateScrollView.pagingEnabled = YES;
49 self.circulateScrollView.delegate = self;
50 self.circulateScrollView.bounces = NO;
51
52 self.circulateScrollView.contentOffset = CGPointMake(ViewWidth, 0);
53
54 self.backgroundColor = [UIColor whiteColor];
55
56 if (!self.imageArray.count) {
57 NSLog(@"图片数组为空");
58 return;
59 }
60
61
62 //若广告数量少于2张则不采用三屏复用技术
63 if (self.imageArray.count<=1){
64 self.circulateScrollView.contentSize = CGSizeMake(ViewWidth, ViewHeight);
65
66 self.endImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, ViewWidth, ViewHeight)];
67 self.endImageView.image = self.imageArray[endImageCount];
68 [self.circulateScrollView addSubview:self.endImageView];
69 [self addSubview:self.circulateScrollView];
70
71 }else{
72 self.circulateScrollView.contentSize = CGSizeMake(ViewWidth*3, ViewHeight);
73
74 //左
75 self.endImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, ViewWidth, ViewHeight)];
76 self.endImageView.image = self.imageArray[endImageCount];
77 [self.circulateScrollView addSubview:self.endImageView];
78 //中
79 self.oneImageView = [[UIImageView alloc]initWithFrame:CGRectMake(ViewWidth, 0, ViewWidth, ViewHeight)];
80 self.oneImageView.image = self.imageArray[oneImageCount];
81 [self.circulateScrollView addSubview:self.oneImageView];
82 //右
83 self.secondImageView = [[UIImageView alloc]initWithFrame:CGRectMake(ViewWidth*2, 0, ViewWidth, ViewHeight)];
84 self.secondImageView.image = self.imageArray[secondImageCount];
85 [self.circulateScrollView addSubview:self.secondImageView];
86
87
88 [self addSubview:self.circulateScrollView];
89 [self pageNumControl];
90 }
91
92 }
93 //添加页符
94 -(void)pageNumControl
95 {
96 self.pageCtl = [[UIPageControl alloc]initWithFrame:CGRectMake(0, ViewHeight-20, ViewWidth, 20)];
97 self.pageCtl.backgroundColor = [UIColor lightGrayColor];
98 self.pageCtl.currentPageIndicatorTintColor = [UIColor greenColor];
99 self.pageCtl.pageIndicatorTintColor = [UIColor whiteColor];
100 self.pageCtl.alpha = 0.7;
101 self.pageCtl.numberOfPages = AllImageCount+1;
102 [self addSubview:self.pageCtl];
103 }
104
105 -(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
106 {
107 if (scrollView.contentOffset.x == 0) {
108 endImageCount--;
109 oneImageCount--;
110 secondImageCount--;
111 if (endImageCount<0) {
112 endImageCount = AllImageCount;
113 }else if (oneImageCount<0){
114 oneImageCount = AllImageCount;
115 }
116 //适配2张图片
117 if (secondImageCount<0){
118 secondImageCount = AllImageCount;
119 }
120 //NSLog(@"endImageCount=%ld oneImageCount=%ld secondImageCount=%ld",endImageCount,oneImageCount,secondImageCount);
121
122 }else if(scrollView.contentOffset.x == ViewWidth*2){
123 endImageCount++;
124 oneImageCount++;
125 secondImageCount++;
126 if (endImageCount>AllImageCount) {
127 endImageCount = 0;
128 }else if (oneImageCount>AllImageCount){
129 oneImageCount = 0;
130 }
131 //适配2张图片
132 if (secondImageCount>AllImageCount){
133 secondImageCount = 0;
134 }
135 }
136 //重新加载显示当前位置的图片
137 scrollView.contentOffset = CGPointMake(ViewWidth, 0);
138 self.endImageView.image = self.imageArray[endImageCount];
139 self.oneImageView.image = self.imageArray[oneImageCount];
140 self.secondImageView.image = self.imageArray[secondImageCount];
141 self.pageCtl.currentPage = oneImageCount;
142 }
143
144 @end