14、无限轮播图

1.SDWebImage提供一个UIImageView的类别以支持加载来自网络的远程图片。具有缓存管理、异步下载、同一个URL下载次数控制和优化等特征

2.目前来说,主要用到了"UIImageView+WebCache.h",给出一个代码示例: 它是UIImageView的一个类目,在要使用它的类中加入#import"UIImageView+WebCache.h"调用 setImageWithURL:placeholderImage:方法。从异步下载到缓存管理，一切都会为你处理。
封装类的.m中

#import "TimerScroller.h"
#import "UIImageView+WebCache.h"
//判断外部传递进来的图片类型
typedef enum:NSUInteger{
    
    ImageNamed=100,
    ImageURL,
    Image,
    
} SourceType;
@interface TimerScroller ()<UIScrollViewDelegate>

@property(nonatomic,retain)UIScrollView* myScrollerView;
@property(nonatomic,retain)UIImageView* leftImg;
@property(nonatomic,retain)UIImageView* centerImg;
@property(nonatomic,retain)UIImageView* rightImg;
@property(nonatomic,assign)int currentIndex;//记录当前显示的图片在数组中的位置
@property(nonatomic,retain)UIPageControl* myPageControl;
@property(nonatomic,retain)NSTimer* myTimer;

@property(nonatomic,assign)SourceType imageType;//图片类型



@end

@implementation TimerScroller

-(NSTimer*)myTimer{
    if (!_myTimer) {
        _myTimer=[NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(changeTimer) userInfo:nil repeats:YES];
        [_myTimer setFireDate:[NSDate distantFuture]];
    }
    return _myTimer;
}

//定时器的回调方法
-(void)changeTimer{
   //先改变偏移量  向右滚
    [self.myScrollerView setContentOffset:CGPointMake(CGRectGetWidth(self.bounds)*2, 0) animated:YES];
    //当前图片+1
    self.currentIndex++;
    //当currentIndex大于数组中的元素个数时，应该让显示第0张
    if (self.currentIndex>=self.allImgsMArray.count) {
        self.currentIndex=0;
    }
    self.myPageControl.currentPage=self.currentIndex;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        
         [self changeImageWithCurrentIndex:self.currentIndex];
    });
    
   
}

-(UIPageControl*)myPageControl{
    if (!_myPageControl) {
        UIView* bgView=[[UIView alloc] initWithFrame:CGRectMake(0, CGRectGetHeight(self.bounds)-30, CGRectGetWidth(self.bounds), 30)];
        _myPageControl=[[UIPageControl alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.bounds), 30)];
        //设置视图的透明度，不会影响上面子视图的透明度
        bgView.backgroundColor=[[UIColor blackColor] colorWithAlphaComponent:0.5];
//        [_myPageControl addTarget:self action:@selector(pageAction:) forControlEvents:(UIControlEventValueChanged)];
        [bgView addSubview:_myPageControl];
        [self addSubview:bgView];
        
    }
    return _myPageControl;
}

//点击图片的回调方法
-(void)selectImg{
//    NSLog(@"%d",self.currentIndex);
    if (self.passBlock) {
        self.passBlock(self.currentIndex);
    }
}


-(UIScrollView*)myScrollerView{
    if (!_myScrollerView) {
        _myScrollerView=[[UIScrollView alloc] initWithFrame:self.bounds];
        _myScrollerView.pagingEnabled=YES;
        _myScrollerView.contentSize=CGSizeMake(CGRectGetWidth(self.bounds)*3, CGRectGetHeight(self.bounds));
        _myScrollerView.directionalLockEnabled=NO;
        //将显示的视图永远是第一屏  (0,1,2)
        _myScrollerView.contentOffset=CGPointMake(CGRectGetWidth(self.bounds), 0);
        _myScrollerView.delegate=self;
        //添加手势
        UITapGestureRecognizer* tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(selectImg)];
        [_myScrollerView addGestureRecognizer:tap];
        [self addSubview:_myScrollerView];
    }
    return _myScrollerView;
}


-(UIImageView*)leftImg{
    if (!_leftImg) {
        _leftImg=[[UIImageView alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.bounds), CGRectGetHeight(self.bounds))];
        [self.myScrollerView addSubview:_leftImg];
        _leftImg.contentMode=UIViewContentModeScaleAspectFit;
    }
    return _leftImg;
}

-(UIImageView*)centerImg{
    if (!_centerImg) {
        _centerImg=[[UIImageView alloc] initWithFrame:CGRectMake(CGRectGetWidth(self.bounds), 0, CGRectGetWidth(self.bounds), CGRectGetHeight(self.bounds))];
        [self.myScrollerView addSubview:_centerImg];
         _centerImg.contentMode=UIViewContentModeScaleAspectFit;
        
    }
    return _centerImg;
}

-(UIImageView*)rightImg{
    if (!_rightImg) {
        _rightImg=[[UIImageView alloc] initWithFrame:CGRectMake(CGRectGetWidth(self.bounds)*2, 0,CGRectGetWidth(self.bounds), CGRectGetHeight(self.bounds))];
        [self.myScrollerView addSubview:_rightImg];
         _rightImg.contentMode=UIViewContentModeScaleAspectFit;
    }
    return _rightImg;
}



-(instancetype)initWithFrame:(CGRect)frame{
    
    self=[super initWithFrame:frame];
    if (self) {
        //为三张图片赋值占位图片
        self.leftImg.image=[UIImage imageNamed:@"01.jpg"];
         self.centerImg.image=[UIImage imageNamed:@"02.jpg"];
         self.rightImg.image=[UIImage imageNamed:@"03.jpeg"];
        
    }
    
    return self;
}


//重写数组的setter方法，当执行setter方法的时候，说明外部给数据了
-(void)setAllImgsMArray:(NSMutableArray *)allImgsMArray{
    
    if (allImgsMArray&&allImgsMArray.count) {
        //判断数据源的类型
        id source=allImgsMArray.firstObject;
        if ([source isKindOfClass:[UIImage class]]) {
            //说明数组元素是图片类型，调用对应的初始化方法
            self.imageType=Image;
            [self sourceIsUIImageWithArray:allImgsMArray];
        }else{
            //说明为字符串
            if ([source hasPrefix:@"http"]) {
                self.imageType=ImageURL;
                [self sourceIsImageURLWithArray:allImgsMArray];
            }else{
                self.imageType=ImageNamed;
                [self sourceIsImageNamedWithArray:allImgsMArray];
            }
        }

    }else{
        NSLog(@"数据源不能为空");
        return;
    }
    
    //当我们确定了数据的个数的时候，才可以确定小白点的个数
     self.myPageControl.numberOfPages=allImgsMArray.count;
    
    _allImgsMArray=allImgsMArray;
   
}

//当数据源为图片名称的时候
-(void)sourceIsImageNamedWithArray:(NSArray*)sourceArray{
    
    if (sourceArray.count==1) {
        //只有一张图片的时候，不能让scrollerView滚动
        self.centerImg.image=[UIImage imageNamed:sourceArray.lastObject];
        self.myScrollerView.pagingEnabled=NO;
        
    }else if (sourceArray.count>=2){
        
        //取出最后一个元素赋值给最左边的
        NSString* last=sourceArray.lastObject;
        self.leftImg.image=[UIImage imageNamed:last];
        
        NSString* first=sourceArray[0];
        self.centerImg.image=[UIImage imageNamed:first];
        self.currentIndex=0;
        NSString* next=sourceArray[1];
        self.rightImg.image=[UIImage imageNamed:next];
        [self.myTimer setFireDate:[NSDate distantPast]];
        
    }
}

//当数据源为图片的URL的时候
-(void)sourceIsImageURLWithArray:(NSArray*)sourceArray{
    
    if (sourceArray.count==1) {
        //只有一张图片的时候，不能让scrollerView滚动
        [self.centerImg sd_setImageWithURL:[NSURL URLWithString:sourceArray.lastObject] placeholderImage:[UIImage imageNamed:@"01.jpg"]];
        self.myScrollerView.pagingEnabled=NO;
        
    }else if (sourceArray.count>=2){
        
        //取出最后一个元素赋值给最左边的
         NSString* last=sourceArray.lastObject;
        [self.leftImg sd_setImageWithURL:[NSURL URLWithString:last] placeholderImage:[UIImage imageNamed:@"02.jpg"]];
        
        NSString* first=sourceArray[0];
         [self.centerImg sd_setImageWithURL:[NSURL URLWithString:first] placeholderImage:[UIImage imageNamed:@"03.jpeg"]];
        self.currentIndex=0;
        
         NSString* next=sourceArray[1];
        [self.rightImg sd_setImageWithURL:[NSURL URLWithString:next] placeholderImage:[UIImage imageNamed:@"03.jpeg"]];
        [self.myTimer setFireDate:[NSDate distantPast]];
        
    }
    
    
    
}

//当数据源为UIImage的时候
-(void)sourceIsUIImageWithArray:(NSArray*)sourceArray{
    
    if (sourceArray.count==1) {
        //只有一张图片的时候，不能让scrollerView滚动
        self.centerImg.image=sourceArray.lastObject;
        self.myScrollerView.pagingEnabled=NO;
    }else if (sourceArray.count>=2){
        //取出最后一个元素赋值给最左边的
        self.leftImg.image=sourceArray.lastObject;
        self.centerImg.image=sourceArray[0];
        self.currentIndex=0;
        self.rightImg.image=sourceArray[1];
        [self.myTimer setFireDate:[NSDate distantPast]];
        
    }

    
}


//停止减速的时候，画面静止会执行的代理方法


-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
   

    //先判断滑动方向
    if (scrollView.contentOffset.x>=CGRectGetWidth(self.bounds)*2) {
        //向右滑动，应该在当前显示的基础上+1
        self.currentIndex++;
    }else if (scrollView.contentOffset.x<=0){
          //向左滑动，应该在当前显示的基础上-1
        self.currentIndex--;
    }
    
    //说明当前显示的为最后一张，在+1就应该显示第0张
    if (self.currentIndex==self.allImgsMArray.count) {
        self.currentIndex=0;
    }
    //说明当前显示的为第0张，在-1，就应该显示最后一张
    if (self.currentIndex<=-1) {
        self.currentIndex=(int)self.allImgsMArray.count-1;
    }
    //当前显示第几张图片，小白点就处于对应的位置
    self.myPageControl.currentPage=self.currentIndex;
    
    //先将显示的图片进行更改
    //将scrollerView的偏移量进行修改
    
    [self changeImageWithCurrentIndex:self.currentIndex];
    //当画面静止几秒
    [self.myTimer setFireDate:[NSDate dateWithTimeIntervalSinceNow:5]];
}


//当用手拖拽的时候会执行的代理方法,（NSTimer不会执行该代理方法）
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    
    
    //将定时器停止
    [self.myTimer setFireDate:[NSDate distantFuture]];
    
    
    
}

//当滚动视图的时候，切换图片调用的方法.整个无限轮播图的算法核心
-(void)changeImageWithCurrentIndex:(int)index{
 
    switch (self.imageType) {
        case ImageNamed:
            [self changeIamgeNamedWithCurrentIndex:index];
            break;
            
        case Image:
            [self changeImageWithCurrentIndex:index];
            break;
            
        case ImageURL:
            [self changeURLWithCurrentIndex:index];
            break;
            
        default:
            break;
    }
    
}



-(void)changeIamgeNamedWithCurrentIndex:(int)index{
    //中间位置需要显示的图片名称
        NSString* center=self.allImgsMArray[index];
        self.centerImg.image=[UIImage imageNamed:center];
         NSString* left;
        NSString* right;
        if (index==0) {
            left=self.allImgsMArray.lastObject;
            right=self.allImgsMArray[index+1];
    
        }else if (index==self.allImgsMArray.count-1) {
            right=self.allImgsMArray.firstObject;
            left=self.allImgsMArray[index-1];
    
        }else{
            left=self.allImgsMArray[index-1];
            right=self.allImgsMArray[index+1];
        }
        self.leftImg.image=[UIImage imageNamed:left];
        self.rightImg.image=[UIImage imageNamed:right];
    
        //将偏移量改回中间位置
        [self.myScrollerView setContentOffset:CGPointMake(CGRectGetWidth(self.bounds), 0) animated:NO];
    
}


-(void)changeURLWithCurrentIndex:(int)index{
    //中间位置需要显示的图片名称
    NSString* center=self.allImgsMArray[index];
    [self.centerImg sd_setImageWithURL:[NSURL URLWithString:center] placeholderImage:[UIImage imageNamed:@"01.jpg"]];
    NSString* left;
    NSString* right;
    if (index==0) {
        left=self.allImgsMArray.lastObject;
        right=self.allImgsMArray[index+1];
        
    }else if (index==self.allImgsMArray.count-1) {
        right=self.allImgsMArray.firstObject;
        left=self.allImgsMArray[index-1];
        
    }else{
        left=self.allImgsMArray[index-1];
        right=self.allImgsMArray[index+1];
    }
    [self.leftImg sd_setImageWithURL:[NSURL URLWithString:left] placeholderImage:[UIImage imageNamed:@"01.jpg"]];
    [self.rightImg sd_setImageWithURL:[NSURL URLWithString:right] placeholderImage:[UIImage imageNamed:@"01.jpg"]];
    
    //将偏移量改回中间位置
    [self.myScrollerView setContentOffset:CGPointMake(CGRectGetWidth(self.bounds), 0) animated:NO];
    
    
    
}


-(void)changeUIImageWithCurrentIndex:(int)index{
    //中间位置需要显示的图片名称
//    NSString* center=self.allImgsMArray[index];
    self.centerImg.image=self.allImgsMArray[index];
    UIImage* left;
    UIImage* right;
    if (index==0) {
        left=self.allImgsMArray.lastObject;
        right=self.allImgsMArray[index+1];
        
    }else if (index==self.allImgsMArray.count-1) {
        right=self.allImgsMArray.firstObject;
        left=self.allImgsMArray[index-1];
        
    }else{
        left=self.allImgsMArray[index-1];
        right=self.allImgsMArray[index+1];
    }
    self.leftImg.image=left;
    self.rightImg.image=right;
    
    //将偏移量改回中间位置
    [self.myScrollerView setContentOffset:CGPointMake(CGRectGetWidth(self.bounds), 0) animated:NO];
    
    
    
}

@end

.h中

#import <UIKit/UIKit.h>

typedef void (^PassBlock)(int currentIndex);

@interface TimerScroller : UIView

@property(nonatomic,retain)NSMutableArray* allImgsMArray;//图片的集合
@property(nonatomic,copy)PassBlock passBlock;//当前位置

@end

运行结果如下

屏幕快照 2017-01-20 上午11.28.52.png