01.轮播图之四 ：imageViews（2 或者 3 个imageview） 轮播

首先说下 3 个imageView的轮播，这个逻辑分析起来 比较简单，

先上传个图片吧：：：：：

主要分析起来，核心就是这样 ：新的图片永远是加在中间ImageView上的，下一轮的第一张图片，是上一轮的第二张图片，这样就可以形成一个无缝滚动了，

  只是切换了数据的逻辑。难理解就算了，看代码才容易懂………………

.h 的声明文件

@interface ImageViewShuffling : UIView

@property (nonatomic,strong)NSArray *array;

@end

.m 的具体实现，这里是理解这个逻辑的好地方————————

@interface ImageViewShuffling ()<UIScrollViewDelegate>

@property (nonatomic,strong)UIScrollView *scrollView;

@property (nonatomic,strong)UIImageView *leftImageView;
@property (nonatomic,strong)UIImageView *centerImageView;
@property (nonatomic,strong)UIImageView *rightImageView;

@property (nonatomic,assign)NSInteger  currentIndex;

@end

@implementation ImageViewShuffling
@synthesize array = _array;

-(instancetype)initWithFrame:(CGRect)frame{
    
    if (self == [super initWithFrame:frame]) {
        self.currentIndex = 0;
    }
    return self;
}

-(UIScrollView*)scrollView{
    
    if (_scrollView == nil) {
        CGRect scrollRect = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
        _scrollView = [[UIScrollView alloc]initWithFrame:scrollRect];
        [self addSubview:_scrollView];
        _scrollView.pagingEnabled = YES;
        _scrollView.delegate = self;
    }
    return _scrollView;
}

-(void)setArray:(NSArray *)array{
    
    NSAssert(array.count != 0, @"传入的滚动数组是 空的");
    _array = array;
    [self initImageViews];
}

-(void)initImageViews{
    
    self.leftImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
    self.centerImageView = [[UIImageView alloc]initWithFrame:CGRectMake(self.frame.size.width, 0, self.frame.size.width, self.frame.size.height)];
    self.rightImageView = [[UIImageView alloc]initWithFrame:CGRectMake(self.frame.size.width*2, 0, self.frame.size.width, self.frame.size.height)];
    self.leftImageView.contentMode = UIViewContentModeScaleAspectFit;
    self.centerImageView.contentMode = UIViewContentModeScaleAspectFit;
    self.rightImageView.contentMode = UIViewContentModeScaleAspectFit;
    
    [self.scrollView addSubview:self.leftImageView];
    [self.scrollView addSubview:self.centerImageView];
    [self.scrollView addSubview:self.rightImageView];
    
/*
千万不要忘记设置这里
*/
    self.scrollView.contentSize = CGSizeMake(self.frame.size.width * 3 , 0);
    self.scrollView.contentOffset = CGPointMake(self.frame.size.width , 0);
   
    [self setImageWith:self.currentIndex];
}

-(void)setImageWith:(NSInteger)integer{
    
    self.centerImageView.backgroundColor = (UIColor*)self.array[integer];
    self.leftImageView.backgroundColor = (UIColor*)self.array[(integer - 1 + self.array.count)%(self.array.count)];
    self.rightImageView.backgroundColor = (UIColor*)self.array[(integer + 1)%(self.array.count)];
}

/**
理解此处，你就能理解整个逻辑实现
*/
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    
    if (scrollView == self.scrollView) {
        
        if (scrollView.contentOffset.x > self.frame.size.width ) {//右滑
            
            self.currentIndex = (self.currentIndex+1) % (self.array.count);
      
        }else  if(scrollView.contentOffset.x < self.frame.size.width ){//左滑
            
            self.currentIndex = (self.currentIndex - 1 + self.array.count)%(self.array.count);
       
        }else{//

        }
        [self setImageWith:self.currentIndex];
        self.scrollView.contentOffset = CGPointMake(self.frame.size.width , 0);
    }
}

上面就是 3张图实现的 轮播图，童叟无欺………………

调用：：：：

-(void)prepareImageViewShuffling{
    
    ImageViewShuffling *imageViewShuffling = [[ImageViewShuffling alloc]initWithFrame:CGRectMake(10, 450, self.view.frame.size.width -20, 220)];
    [self.view addSubview:imageViewShuffling];;
    imageViewShuffling.array = self.arr;
}

********************************************************************************

弄懂了上面这个，相信下面介绍这个两张图片实现的轮播 ，对你就是小case

他就是对上面3张图片的简化…………

看完上面的逻辑，理解后发现, 左侧，或者右侧的 imageView 始终有一个是备用的，就像实现的代码一样，你不是向左就是向右滑动；

根据这个理由，就想到了这个，实时检测scroll 的滚动方向，这样就可以实现：一个主要显示的imageView，和一个 待显示的imageView……

越说越啰嗦，直接撸代码……

.h 文件

@interface ImageView2Shuffling : UIView
@property (nonatomic,strong)NSArray *array;

@end

.m 实现文件，逻辑变化不大

@interface ImageView2Shuffling ()<UIScrollViewDelegate>

@property (nonatomic,strong)UIScrollView *scrollView;

@property (nonatomic,strong)UIImageView *currentImageView;
@property (nonatomic,strong)UIImageView *otherImageView;
@property (nonatomic,assign)NSInteger  currentIndex;
/*
这个是检测滚动方向的
*/
@property (nonatomic,strong)NSString *directionString;
@end

@implementation ImageView2Shuffling
@synthesize array = _array;

-(instancetype)initWithFrame:(CGRect)frame{
    
    if (self == [super initWithFrame:frame]) {
        self.currentIndex = 0;
        self.directionString = [[NSString alloc]init];
    }
    return self;
}

-(UIScrollView*)scrollView{
    
    if (_scrollView == nil) {
        CGRect scrollRect = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
        _scrollView = [[UIScrollView alloc]initWithFrame:scrollRect];
        [self addSubview:_scrollView];
        _scrollView.pagingEnabled = YES;
        _scrollView.delegate = self;
    }
    return _scrollView;
}

-(void)setArray:(NSArray *)array{
    
    NSAssert(array.count != 0, @"传入的滚动数组是 空的");
    _array = array;
    [self initImageViews];
}

-(void)initImageViews{
    /*
这里写个空 frame 的imageview
   */
    self.otherImageView = [[UIImageView alloc]init];
    [self.scrollView addSubview:self.otherImageView];

    self.currentImageView = [[UIImageView alloc]initWithFrame:CGRectMake(self.frame.size.width, 0, self.frame.size.width, self.frame.size.height)];
    self.currentImageView.contentMode = UIViewContentModeScaleAspectFit;
    [self.scrollView addSubview:self.currentImageView];
    
    self.scrollView.contentSize = CGSizeMake(self.frame.size.width * 3 , 0);
    self.scrollView.contentOffset = CGPointMake(self.frame.size.width , 0);
    
    [self setImageWith:self.currentIndex];
}


-(void)setImageWith:(NSInteger)integer{
    
    self.currentImageView.backgroundColor = (UIColor*)self.array[integer];
}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    
    if (scrollView == self.scrollView) {
        
        self.directionString = @"";
        
        if (scrollView.contentOffset.x > self.frame.size.width ) {//右滑
            
            self.currentIndex = (self.currentIndex+1) % (self.array.count);
            
        }else  if(scrollView.contentOffset.x < self.frame.size.width ){//左滑
            
            self.currentIndex = (self.currentIndex - 1 + self.array.count)%(self.array.count);
        }else{//
        }
        [self setImageWith:self.currentIndex];
        self.scrollView.contentOffset = CGPointMake(self.frame.size.width , 0);
    }
}

/*
这里集中了些 修改的代码
检测滚动方向，改变otherImageview 的位置，和颜色
*/
-(void)scrollViewDidScroll:(UIScrollView *)scrollView{

    if (scrollView == self.scrollView) {
        
        if (scrollView.contentOffset.x > self.frame.size.width ) {//右滑
           
            [self refreshOtherImageViewWithDirectionString:@"right"];
        }else  if(scrollView.contentOffset.x < self.frame.size.width ){//左滑
            
            [self refreshOtherImageViewWithDirectionString:@"left"];
        }else{//
        }
    }
}

-(void)refreshOtherImageViewWithDirectionString:(NSString*)direction{

    if ([self.directionString isEqualToString:direction]) {
        return ;
    }
    self.directionString = direction;
   
    CGRect frame; NSInteger integer;
    if ([direction isEqualToString:@"right"]) {
        
        integer = (self.currentIndex+1) % (self.array.count);
        frame = CGRectMake(self.frame.size.width*2, 0, self.frame.size.width, self.frame.size.height);
    }else{ //if "left"
    
        integer = (self.currentIndex - 1 + self.array.count)%(self.array.count);
        frame = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
    }
    self.otherImageView.backgroundColor = (UIColor*)self.array[integer];
    self.otherImageView.frame = frame;
}

写到这里，应该可以了，简单来讲，就是用一个direction 替换了一个imageview ，应该算减少了UI 的开销，增加了逻辑判断和运算

调用：：：：

-(void)prepareImageView2Shuffling{
    
    ImageView2Shuffling *imageView2Shuffling = [[ImageView2Shuffling alloc]initWithFrame:CGRectMake(10, 450, self.view.frame.size.width -20, 220)];
    [self.view addSubview:imageView2Shuffling];;
    imageView2Shuffling.array = self.arr;
}

突然感觉要超额完成任务的节拍，为自己加油点赞………………