三个ImageView 实现无线轮播 方法

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //开始滚动，判断位置，然后替换复用的三张图
    [self changeImageWithOffset:scrollView.contentOffset.x];
}

- (void)changeImageWithOffset:(CGFloat)offsetX
{
    if (offsetX >= ScrollWidth * 2)
    {
        _currentIndex++;
        
        if (_currentIndex == _MaxImageCount-1)
        {
            [self changeImageLeft:_currentIndex-1 center:_currentIndex right:0];
            
        }else if (_currentIndex == _MaxImageCount)
        {
            
            _currentIndex = 0;
            
            [self changeImageLeft:_MaxImageCount-1 center:0 right:1];
            
        }else
        {
            [self changeImageLeft:_currentIndex-1 center:_currentIndex right:_currentIndex+1];
        }
        _PageControl.currentPage = _currentIndex;
        
    }
    
    if (offsetX <= 0)
    {
        _currentIndex--;
        
        if (_currentIndex == 0) {
            
            [self changeImageLeft:_MaxImageCount-1 center:0 right:1];
            
        }else if (_currentIndex == -1) {
            
            _currentIndex = _MaxImageCount-1;
            [self changeImageLeft:_currentIndex-1 center:_currentIndex right:0];
            
        }else {
            [self changeImageLeft:_currentIndex-1 center:_currentIndex right:_currentIndex+1];
        }
        
        _PageControl.currentPage = _currentIndex;
    }
}

#pragma mark - 给复用的imageView赋值

- (void)changeImageLeft:(NSInteger)LeftIndex center:(NSInteger)centerIndex right:(NSInteger)rightIndex
{
    if (_isNetworkImage)
    {
        
        [_leftImageView sd_setImageWithURL:[NSURL URLWithString:_imageArray[LeftIndex]] placeholderImage:_placeholderImage];
        [_centerImageView sd_setImageWithURL:[NSURL URLWithString:_imageArray[centerIndex]] placeholderImage:_placeholderImage];
        [_rightImageView sd_setImageWithURL:[NSURL URLWithString:_imageArray[rightIndex]] placeholderImage:_placeholderImage];
        
    }else
    {
        _leftImageView.image = _imageArray[LeftIndex];
        _centerImageView.image = _imageArray[centerIndex];
        _rightImageView.image = _imageArray[rightIndex];
    }
    
    [_scrollView setContentOffset:CGPointMake(ScrollWidth, 0)];
}