iOS实现三屏复用循环广告[从服务器请求的广告]

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

 #import <UIKit/UIKit.h>
 
 @interface CirculateScrollview : UIView
 
 @property (nonatomic,strong)NSMutableArray *imageArray;//图片数组
 @property (nonatomic,strong)UIScrollView *circulateScrollView;//广告
 
 /*
  三屏复用广告
  适用范围:网络请求或固定本地的广告图片
         适用所有数量广告，广告>=2时自动采用三屏复用技术
  使用方法:例
  在需要添加广告的控制器里面
 
  CirculateScrollview *cview = [[CirculateScrollview alloc]initWithFrame:CGRectMake(0, 20, 320, 200)];
  for (int i=0; i<3; i++) {
  UIImage *image = [UIImage imageNamed:@"旅行图1"];//传进图片名字方式
  //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
  [cview.imageArray addObject:image];
  }
  [self.view addSubview:cview];
 
  */
 
 /*
  图片转换NSData方法
  测试可用
  NSData * data = UIImageJPEGRepresentation(image, 1);
  */
 
 @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

 #import "CirculateScrollview.h"
 
 #define ViewWidth self.frame.size.width
 #define ViewHeight self.frame.size.height
 #define AllImageCount self.imageArray.count-1
 
 @interface CirculateScrollview()<UIScrollViewDelegate>
 {
     NSInteger endImageCount;//左边图片
     NSInteger oneImageCount;//中间图片[当前看到的图片]
     NSInteger secondImageCount;//右边图片
 }
 @property (nonatomic,strong)UIImageView *endImageView;
 @property (nonatomic,strong)UIImageView *oneImageView;
 @property (nonatomic,strong)UIImageView *secondImageView;
 @property (nonatomic,strong)UIPageControl *pageCtl;
 
 @end
 
 @implementation CirculateScrollview
 
 -(id)initWithFrame:(CGRect)frame
 {
     self = [super initWithFrame:frame];
     if (self) {
 
     }
     return self;
 }
 
 -(NSMutableArray *)imageArray
 {
     if (!_imageArray) {
         _imageArray = [[NSMutableArray alloc]init];
     }
     return _imageArray;
 }
 
 - (void)drawRect:(CGRect)rect {
     self.circulateScrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(, , ViewWidth, ViewHeight)];
 
     endImageCount = self.imageArray.count-;
     oneImageCount = ;
     secondImageCount = ;
 
     self.circulateScrollView.showsHorizontalScrollIndicator = NO;
     self.circulateScrollView.pagingEnabled = YES;
     self.circulateScrollView.delegate = self;
     self.circulateScrollView.bounces = NO;
 
     self.circulateScrollView.contentOffset = CGPointMake(ViewWidth, );
 
     self.backgroundColor = [UIColor whiteColor];
 
     if (!self.imageArray.count) {
         NSLog(@"图片数组为空");
         return;
     }
 
     //若广告数量少于2张则不采用三屏复用技术
     if (self.imageArray.count<=){
         self.circulateScrollView.contentSize = CGSizeMake(ViewWidth, ViewHeight);
 
         self.endImageView = [[UIImageView alloc]initWithFrame:CGRectMake(, , ViewWidth, ViewHeight)];
         self.endImageView.image = self.imageArray[endImageCount];
         [self.circulateScrollView addSubview:self.endImageView];
         [self addSubview:self.circulateScrollView];
 
     }else{
         self.circulateScrollView.contentSize = CGSizeMake(ViewWidth*, ViewHeight);
 
         //左
         self.endImageView = [[UIImageView alloc]initWithFrame:CGRectMake(, , ViewWidth, ViewHeight)];
         self.endImageView.image = self.imageArray[endImageCount];
         [self.circulateScrollView addSubview:self.endImageView];
         //中
         self.oneImageView = [[UIImageView alloc]initWithFrame:CGRectMake(ViewWidth, , ViewWidth, ViewHeight)];
         self.oneImageView.image = self.imageArray[oneImageCount];
         [self.circulateScrollView addSubview:self.oneImageView];
         //右
         self.secondImageView = [[UIImageView alloc]initWithFrame:CGRectMake(ViewWidth*, , ViewWidth, ViewHeight)];
         self.secondImageView.image = self.imageArray[secondImageCount];
         [self.circulateScrollView addSubview:self.secondImageView];
 
         [self addSubview:self.circulateScrollView];
         [self pageNumControl];
     }
 
 }
 //添加页符
 -(void)pageNumControl
 {
     self.pageCtl = [[UIPageControl alloc]initWithFrame:CGRectMake(, ViewHeight-, ViewWidth, )];
     self.pageCtl.backgroundColor = [UIColor lightGrayColor];
     self.pageCtl.currentPageIndicatorTintColor = [UIColor greenColor];
     self.pageCtl.pageIndicatorTintColor = [UIColor whiteColor];
     self.pageCtl.alpha = 0.7;
     self.pageCtl.numberOfPages = AllImageCount+;
     [self addSubview:self.pageCtl];
 }
 
 -(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
 {
     if (scrollView.contentOffset.x == ) {
         endImageCount--;
         oneImageCount--;
         secondImageCount--;
         if (endImageCount<) {
             endImageCount = AllImageCount;
         }else if (oneImageCount<){
             oneImageCount = AllImageCount;
         }
         //适配2张图片
         if (secondImageCount<){
             secondImageCount = AllImageCount;
         }
         //NSLog(@"endImageCount=%ld  oneImageCount=%ld  secondImageCount=%ld",endImageCount,oneImageCount,secondImageCount);
 
     }else if(scrollView.contentOffset.x == ViewWidth*){
         endImageCount++;
         oneImageCount++;
         secondImageCount++;
         if (endImageCount>AllImageCount) {
             endImageCount = ;
         }else if (oneImageCount>AllImageCount){
             oneImageCount = ;
         }
         //适配2张图片
         if (secondImageCount>AllImageCount){
             secondImageCount = ;
         }
     }
     //重新加载显示当前位置的图片
     scrollView.contentOffset = CGPointMake(ViewWidth, );
     self.endImageView.image = self.imageArray[endImageCount];
     self.oneImageView.image = self.imageArray[oneImageCount];
     self.secondImageView.image = self.imageArray[secondImageCount];
     self.pageCtl.currentPage = oneImageCount;
 }
 
 @end