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。