首先，新建一个PageView.xib，在该xib的View里放上一个UILabel，并在IB里把它的tag设置为1：

然后，新建一个带xib文件的Controller，在这个Controller的xib里的View放上一个UIScrollView，frame和View一样大：

把刚才那个UIScrollView关联到Controller文件里，再开始写initView函数，初始化三个UIView，把他们添加到UIScrollView，然后设置UIScrollView宽度为三页，并让UIScrollView显示第二页：

_pageFirst = [[[NSBundle mainBundle] loadNibNamed:@"PageView" owner:self options:nil] lastObject]; UILabel *labelTitle = (UILabel *)[_pageFirst viewWithTag:1]; labelTitle.text = @"fistPage"; _pageSecond = [[[NSBundle mainBundle] loadNibNamed:@"PageView" owner:self options:nil] lastObject]; labelTitle = (UILabel *)[_pageSecond viewWithTag:1]; labelTitle.text = @"secondPage"; _pageThird = [[[NSBundle mainBundle] loadNibNamed:@"PageView" owner:self options:nil] lastObject]; labelTitle = (UILabel *)[_pageThird viewWithTag:1]; labelTitle.text = @"thirdPage"; [self setPageFrame]; [_scrollView addSubview:_pageFirst]; [_scrollView addSubview:_pageSecond]; [_scrollView addSubview:_pageThird]; _scrollView.pagingEnabled = YES; _scrollView.contentSize = CGSizeMake(_scrollView.frame.size.width * 3, _scrollView.frame.size.height); _scrollView.showsVerticalScrollIndicator = NO; _scrollView.showsHorizontalScrollIndicator = NO; _scrollView.delegate = self; //scroll to the second page CGPoint p = CGPointZero; p.x = _scrollView.frame.size.width; [_scrollView setContentOffset:p animated:NO];

下面是setPageFrame方法：

         _pageFirst.frame = CGRectMake(_scrollView.frame.origin.x, _scrollView.frame.origin.y, _scrollView.frame.size.width, _scrollView.frame.size.height); _pageSecond.frame = CGRectMake(_scrollView.frame.origin.x + _scrollView.frame.size.width, _scrollView.frame.origin.y, _scrollView.frame.size.width, _scrollView.frame.size.height); _pageThird.frame = CGRectMake(_scrollView.frame.origin.x + _scrollView.frame.size.width * 2, _scrollView.frame.origin.y, _scrollView.frame.size.width, _scrollView.frame.size.height);

接下来实现UIScrollView的delegate：- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView。首先通过UIScrollView的contentOffset和frame的width属性计算得到UIScrollView滚动停止时候的显示页面，如果是第二页，则说明没有翻页，不作处理，如果是第一页或者第三页，则UIScrollView的三个subView的顺序依次向右或向左移动，并且继续让UIScrollView显示第二页：

    CGFloat pageWidth = scrollView.frame.size.width; // 0 1 2 int page = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1; if(page == 1) { return; } else if (page == 0) { [self pageMoveToRight]; } else { [self pageMoveToLeft]; } CGPoint p = CGPointZero; p.x = pageWidth; [scrollView setContentOffset:p animated:NO];

依次向右或向左移动UIScrollView的subView方法：

- (void)pageMoveToRight { UIView *tmp = _pageSecond; _pageSecond = _pageFirst; _pageFirst = _pageThird; _pageThird = tmp; [self setPageFrame]; } - (void)pageMoveToLeft { UIView *tmp = _pageSecond; _pageSecond = _pageThird; _pageThird = _pageFirst; _pageFirst = tmp; [self setPageFrame]; }

本文所有代码下载链接：http://download.csdn.net/detail/i2c_rs485/4394375，我使用xcode4.3.2

我参考过的资料：

http://www.cocoachina.com/bbs/read.php?tid=7013&page=2   cocoachina的讨论

http://www.dreamingwish.com/dream-2011/uiscrollview-infinite-loop-scrolling.html  我都是从这篇文章学习到的正确方法，强烈建议你们也看一下，感谢Seven's！

        DM8168 HDVPSS的VIP Parser模块(2)

      此属性可以强制修改gcc的对齐方式

      一般软件的2进制协议中，会定义一系列的规范，32位机一般会定义4字节对齐的协议，这样对于32位机来说速度是最快的。

      最近发现gcc一个问题，在一个结构体包含unsignd long long （64位）类型时会导致结构体8字节对齐，且__attribute__ ((aligned(4))) 

竟然无效

      本例子用的x86 编译器版本

#gcc --version gcc (GCC) 4.1.3 20080704 (prerelease) (Debian 4.1.2-25) Copyright (C) 2006 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

# arm-linux-gcc --version arm-linux-gcc ((gcc4.4-290+uclibc_0.9.32.1+eabi+linuxpthread)) 4.4.1 Copyright (C) 2009 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

      直接上例子程序

#include <stdio.h> typedef unsigned long long ullong; typedef struct { char a; ullong b; int c; /*} __attribute__ ((packed)) test ;*/ /*} __attribute__ ((aligned (4))) test ;*/ } test; int main ( int argc, char *argv[] ) { printf("file:%s, line:%d, sizeof(test):%d\n", __FILE__, __LINE__, sizeof(test)); return 0; }x86 32运行结果

file:test.c, line:15, sizeof(test):16arm contex A9 运行结果

file:test.c, line:15, sizeof(test):24
结果说明在arm编译器成了8字节对齐 x86编译器还是4字节对齐

为了让该结构体4字节对齐，我们采用

__attribute__ ((aligned (4)))

强制对齐

输出结果还是

file:test.c, line:15, sizeof(test):24无奈使用单字节对齐

__attribute__ ((aligned (4))) test输出结果为

file:test.c, line:15, sizeof(test):13
这样虽然解决了我们4字节对齐的问题，但是这样 我们得严格注意结构体对齐的问题。