iOS实现无限循环图片轮播器的封装

项目中很多时候会碰到这个需求，实现多张图片的无限循环轮转，以前做过，项目中几个地方的都用到了，当时没有封装，几个地方都拷贝几乎一样的代码，代码复用性不好，今天没事封装了一下，使用起来比较简单。

首先，说说我实现循环轮转图片的思想，在UIScrollView中添加了3个UIImageView，并排排列，我们看到的永远只是第二个UIImageView，这样的话，你一直可以向左，向右滑动，当你向左滑动是，这是你滑动到了最后一个UIImageView不能在向左边滑动了，这时，我在后面悄悄的将第二个UIImageView图片设置为当前要显示的图片，调整UIScrollView的contentOffset属性，如：

[_contentScrollView setContentOffset:CGPointMake(self.bounds.size.width, 0) animated:NO]（使用者根本感觉不出来这种变化）所以，此时，你看到的又是第二个UIImageView，所以此时你又可以向左滑动，当你向右边滑动时候处理类似，导致结果你可以向左边，右边无线循环轮转图片。

JGCirculateSwitchImgView.h头文件

@interface JGCirculateSwitchImgView : UIView

@property(nonatomic,strong)NSArray *imgUrlArr;

@end

头文件中只有一个需要设置的成员变量imgUrlArr数组，就是你要显示图片路径的数组，将通过这个数组访问图片。

JGCirculateSwitchImgView.m文件

typedef NS_ENUM(NSInteger, SwitchDirection)

{

//未成功旋转

  SwitchDirectionNone = -1,

//向右旋转图片

 SwitchDirectionRight = 0,

//向左训转图片

SwitchDirectionLeft = 1,

};

定义了SwitchDirection枚举，表示图片向左，向右轮转，或者什么也不做。

//默认5秒训转图片一次,可以根据需要改变

#define WiatForSwitchImgMaxTime 5

#import "JGCirculateSwitchImgView.h"

#import "UIImageView+WebCache.h"

@interface JGCirculateSwitchImgView ()

//底部UIScrollView

@property(nonatomic,weak)UIScrollView *contentScrollView;

//显示页码的UIPageControl控件

@property(nonatomic,weak)UIPageControl *pageControlView;

//用保存当前UIPageControl控件显示的当前位置

@property(nonatomic,assign)NSInteger currentPage;

//用于保存当前显示图片在图片urlArr数组中的索引

@property(nonatomic,assign)NSInteger currentImgIndex;

//UIScrollView上的三个UIImgaView这里通过3个UIImageView实现无限循环图片轮转

@property(nonatomic,weak)UIImageView *imgView1;

@property(nonatomic,weak)UIImageView *imgView2;

@property(nonatomic,weak)UIImageView *imgView3;

@property(nonatomic,assign)BOOL isDragImgView;

//SwitchDirection类型，用于保存滑动的方向

@property(nonatomic,assign)SwitchDirection swDirection;

@end

-(id)initWithFrame:(CGRect)frame

{

    if (self = [super initWithFrame:frame])

    {

       [self createContentScrollView];

       [self createPageControlView];

      //默认第一页

      _currentPage = 0;

      //默认显示第一张图片

      _currentImgIndex = 0;

     _isDragImgView = NO;

     _swDirection = SwitchDirectionNone;

   }

     return self;

}

创建UIScrollView代码

-(void)createContentScrollView

{

    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.bounds];

    scrollView.delegate = self;

    scrollView.showsHorizontalScrollIndicator = NO;

    scrollView.shouldGroupAccessibilityChildren = NO;

    scrollView.pagingEnabled = YES;

    [self addSubview:scrollView];

    _contentScrollView = scrollView;

}

创建UIPageControl

-(void)createPageControlView

{

    UIPageControl *pageControlVw = [[UIPageControl alloc] init];

   pageControlVw.frame = CGRectMake(0, 0, 80, 20);

   pageControlVw.center = CGPointMake(self.center.x, self.bounds.size.height - 20);

   pageControlVw.backgroundColor = [UIColor redColor];

   _pageControlView.pageIndicatorTintColor = [UIColor yellowColor];

   _pageControlView.currentPageIndicatorTintColor = [UIColor purpleColor];

   [self addSubview:pageControlVw];

   _pageControlView = pageControlVw;

}

//value对Count取模,并保证为正值

//这里很重要，是实现无限循环的重要的一步，比如现在显示的是第一张图片，_currentImgIndex=0,向左滑动后就显示_currentImgIndex+1张图片，可是_currentImgIndex+1可能回大于_imgUrlArr的数组count，这里取模，其次还要保证为正数，比如，如果向右边滑动是就显示_currentImgIndex-1张图片，_currentImgIndex-1取模也可能为负数，此时加上count保证为正数

-(NSInteger)switchToMValue:(NSInteger)value Count:(NSInteger)count

{

    NSInteger result = value % count;

    return result >=0 ? result : result + count;

}

重写imgUrlArr的set方法

-(void)setImgUrlArr:(NSArray *)imgUrlArr

{

    _imgUrlArr = [imgUrlArr copy];

    NSInteger count = imgUrlArr.count;

    if (count <= 0 )

    {

      return;

    }

   //如果只显示一张图片,那就没有旋转情况

   if (count == 1)

   {

       UIImageView *imgView = [[UIImageView alloc]init];

       imgView.frame = CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height);

      [_contentScrollView addSubview:imgView]; 

      _pageControlView.numberOfPages = 1; 

      _pageControlView.currentPage = 0;

      _contentScrollView.contentSize = CGSizeMake(self.bounds.size.width, self.bounds.size.height);

      NSURL *imgUrl = [NSURL URLWithString:imgUrlArr[0]];

     [imgView sd_setImageWithURL:imgUrl placeholderImage:nil];

     return;

   }

   if (count > 1)

   {

         //这里只使用3个ImgView轮转多张图片，数量2,3,4,5,6...

         for(int i = 0; i < 3 ;i++)

         {

             UIImageView *imgView = [[UIImageView alloc] init];

             imgView.frame = CGRectMake(i * self.bounds.size.width, 0, self.bounds.size.width, self.bounds.size.height);

             imgView.layer.masksToBounds = YES;

             NSString *urlStr = urlStr = _imgUrlArr[[self switchToValue:i-1 Count:count]];

             NSURL *imgUrl = [NSURL URLWithString:urlStr];

              [imgView sd_setImageWithURL:imgUrl placeholderImage:nil];

              if (i == 0)

              {

                  _imgView1 = imgView; 

               }

               else if (i == 1)

              {

                  _imgView2 = imgView;

              }

              else if (i == 2)

              {

                 _imgView3 = imgView; 

              }

              [_contentScrollView addSubview:imgView];

         }

        _pageControlView.numberOfPages = count; 

        _pageControlView.currentPage = 0;

        _contentScrollView.contentSize = CGSizeMake(self.bounds.size.width * 3,   self.bounds.size.height);

        _currentImgIndex = 0;

       [_contentScrollView setContentOffset:CGPointMake(self.bounds.size.width, 0) animated:NO];

      dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),  ^{

           //循环轮转图片

           [self switchImg];

     });

   }

}

5秒旋转图片

-(void)switchImg

{

     while (1)

     {

          [NSThread sleepForTimeInterval:WiatForSwitchImgMaxTime];

          //如果正在拖拽图片，此次作废 

           if (_isDragImgView) {

               continue;

           }

            _currentPage = [self switchToValue:_currentPage + 1 Count:_imgUrlArr.count];

            dispatch_async(dispatch_get_main_queue(), ^{

                  _pageControlView.currentPage = _currentPage;

                 _contentScrollView.contentOffset = CGPointMake(2 * self.bounds.size.width, 0);

                 [self reSetImgUrlWithDirection:SwitchDirectionLeft];

         });

     }

}

当手动旋转图片

-(void)switchImgByDirection:(SwitchDirection)direction

{

     if (direction == SwitchDirectionNone) {

         return;

     }

     [self reSetImgUrlWithDirection:direction];

     [_contentScrollView setContentOffset:CGPointMake(self.bounds.size.width, 0) animated:NO];

}

旋转图片后重新调整3个UIImageView显示的内容，如实现思想所述

-(void)reSetImgUrlWithDirection:(SwitchDirection)direction

{

     if (direction == SwitchDirectionRight) {

         [_imgView1 sd_setImageWithURL:[NSURL URLWithString:_imgUrlArr[[self switchToValue:_currentImgIndex - 2 Count:_imgUrlArr.count]]] placeholderImage:nil];

         [_imgView2 sd_setImageWithURL:[NSURL URLWithString:_imgUrlArr[[self switchToValue:_currentImgIndex - 1 Count:_imgUrlArr.count]]] placeholderImage:nil];

         [_imgView3 sd_setImageWithURL:[NSURL URLWithString:_imgUrlArr[[self switchToValue:_currentImgIndex Count:_imgUrlArr.count]]] placeholderImage:nil];

         _currentImgIndex = [self switchToValue:_currentImgIndex - 1 Count:_imgUrlArr.count];

      }

     else if(direction == SwitchDirectionLeft)

     {

          [_imgView1 sd_setImageWithURL:[NSURL URLWithString:_imgUrlArr[[self switchToValue:_currentImgIndex Count:_imgUrlArr.count]]] placeholderImage:nil];

          [_imgView2 sd_setImageWithURL:[NSURL URLWithString:_imgUrlArr[[self switchToValue:_currentImgIndex + 1 Count:_imgUrlArr.count]]] placeholderImage:nil];

          [_imgView3 sd_setImageWithURL:[NSURL URLWithString:_imgUrlArr[[self switchToValue:_currentImgIndex + 2 Count:_imgUrlArr.count]]] placeholderImage:nil];

          _currentImgIndex = [self switchToValue:_currentImgIndex + 1 Count:_imgUrlArr.count];

     }

}

实现UIScrollVie3个代理方法

#pragma mark -------------Delegate---------------

//记住滑动的方向

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

    static float newx = 0;

    static float oldx = 0;

   newx= scrollView.contentOffset.x ;

   if (newx != oldx )

   {

       if (newx > oldx)

       {

           _swDirection = SwitchDirectionLeft;

       }else if(newx < oldx)

      {

          _swDirection = SwitchDirectionRight;

      }

      oldx = newx;

   }

}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView

{

    _isDragImgView = YES;

}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView

{

     //向左旋转

     if (_swDirection == SwitchDirectionLeft)

     {

          _currentPage = [self switchToValue:_currentPage + 1 Count:_imgUrlArr.count];

     }//向右旋转

     else if (_swDirection == SwitchDirectionRight)

     {

         _currentPage = [self switchToValue:_currentPage - 1 Count:_imgUrlArr.count];

     }

     _pageControlView.currentPage = _currentPage;

     if (_swDirection != SwitchDirectionNone) {

     [self switchImgByDirection:_swDirection];

     }

    _isDragImgView = NO;

}

以上为实现代码，现在看看怎么用，例如：

JGCirculateSwitchImgView *jView = [[JGCirculateSwitchImgView alloc] initWithFrame:CGRectMake(20,100, 280, 250)];

NSArray *imgUrlArr = @[@"http://www.blisscake.cn/Upload/Product/Show/Source/ps_1507201119031647109.jpg",

@"http://www.blisscake.cn/Upload/Product/Show/Source/ps_1507201116215754685.jpg",

@"http://www.blisscake.cn/Upload/Product/Show/Source/ps_1507201115524758041.jpg",

@"http://www.blisscake.cn/Upload/Product/Show/Source/ps_1507201114495822068.jpg",

@"http://www.blisscake.cn/Upload/Product/Show/Source/ps_1507201107522493367.jpg"];

jView.imgUrlArr = imgUrlArr;

[self.view addSubview:jView];

可以看到封装之后，代码的重用性很高，使用起来很简单，就这么4句代码就可以实现图片的无限循环轮转。

以上就是本文的全部内容，希望对大家的学习有所帮助。