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(0, 0, ViewWidth, ViewHeight)];
    
    endImageCount = self.imageArray.count-1;
    oneImageCount = 0;
    secondImageCount = 1;
    
    self.circulateScrollView.showsHorizontalScrollIndicator = NO;
    self.circulateScrollView.pagingEnabled = YES;
    self.circulateScrollView.delegate = self;
    self.circulateScrollView.bounces = NO;
    
    self.circulateScrollView.contentOffset = CGPointMake(ViewWidth, 0);
    
    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<=1){
        self.circulateScrollView.contentSize = CGSizeMake(ViewWidth, ViewHeight);
        
        self.endImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, ViewWidth, ViewHeight)];
        self.endImageView.image = self.imageArray[endImageCount];
        [self.circulateScrollView addSubview:self.endImageView];
        [self addSubview:self.circulateScrollView];
        
    }else{
        self.circulateScrollView.contentSize = CGSizeMake(ViewWidth*3, ViewHeight);
        
        //左
        self.endImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, ViewWidth, ViewHeight)];
        self.endImageView.image = self.imageArray[endImageCount];
        [self.circulateScrollView addSubview:self.endImageView];
        //中
        self.oneImageView = [[UIImageView alloc]initWithFrame:CGRectMake(ViewWidth, 0, ViewWidth, ViewHeight)];
        self.oneImageView.image = self.imageArray[oneImageCount];
        [self.circulateScrollView addSubview:self.oneImageView];
        //右
        self.secondImageView = [[UIImageView alloc]initWithFrame:CGRectMake(ViewWidth*2, 0, 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(0, ViewHeight-20, ViewWidth, 20)];
    self.pageCtl.backgroundColor = [UIColor lightGrayColor];
    self.pageCtl.currentPageIndicatorTintColor = [UIColor greenColor];
    self.pageCtl.pageIndicatorTintColor = [UIColor whiteColor];
    self.pageCtl.alpha = 0.7;
    self.pageCtl.numberOfPages = AllImageCount+1;
    [self addSubview:self.pageCtl];
}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    if (scrollView.contentOffset.x == 0) {
        endImageCount--;
        oneImageCount--;
        secondImageCount--;
        if (endImageCount<0) {
            endImageCount = AllImageCount;
        }else if (oneImageCount<0){
            oneImageCount = AllImageCount;
        }
        //适配2张图片
        if (secondImageCount<0){
            secondImageCount = AllImageCount;
        }
        //NSLog(@"endImageCount=%ld  oneImageCount=%ld  secondImageCount=%ld",endImageCount,oneImageCount,secondImageCount);
        
    }else if(scrollView.contentOffset.x == ViewWidth*2){
        endImageCount++;
        oneImageCount++;
        secondImageCount++;
        if (endImageCount>AllImageCount) {
            endImageCount = 0;
        }else if (oneImageCount>AllImageCount){
            oneImageCount = 0;
        }
        //适配2张图片
        if (secondImageCount>AllImageCount){
            secondImageCount = 0;
        }
    }
    //重新加载显示当前位置的图片
    scrollView.contentOffset = CGPointMake(ViewWidth, 0);
    self.endImageView.image = self.imageArray[endImageCount];
    self.oneImageView.image = self.imageArray[oneImageCount];
    self.secondImageView.image = self.imageArray[secondImageCount];
    self.pageCtl.currentPage = oneImageCount;
}

@end