翻页效果，类似下面的样子：
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在电子书应用中会很常见。这里需要两个要点：在电子书应用中会很常见。这里需要两个要点：
翻页动画
手势上下轻扫（swipe）的处理
先说一下轻扫（swipe）的实现，可以参考编写简单的手势示例：Tap了解手势种类。
在viewDidLoad方法中注册了对上、下、左、右四个方向轻松的处理方法：
- (void)viewDidLoad {
???
??? UISwipeGestureRecognizer *recognizer;
???
??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionRight)];
??? [[self view] addGestureRecognizer:recognizer];
??? [recognizer release];
???
??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionUp)];
??? [[self view] addGestureRecognizer:recognizer];
??? [recognizer release];
???
??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionDown)];
??? [[self view] addGestureRecognizer:recognizer];
??? [recognizer release];
???
??? recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipeFrom:)];
??? [recognizer setDirection:(UISwipeGestureRecognizerDirectionLeft)];
??? [[self view] addGestureRecognizer:recognizer];
??? [recognizer release];
???
???
??? [super viewDidLoad];
可以看到，都是同一个方法，handleSwipeFrom。
在该方法中，再识别具体是哪个方向的轻扫手势，比如判断是向下的轻扫：
-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {
??? NSLog(@"Swipe received.");
???
??? if (recognizer.direction==UISwipeGestureRecognizerDirectionDown) {
??????? NSLog(@"swipe down");
判断是向上的轻扫：
if (recognizer.direction==UISwipeGestureRecognizerDirectionUp) {
??? NSLog(@"swipe up");
有关动画的处理，比如向下（往回）翻页，类似这样：
[UIView beginAnimations:@"animationID" context:nil];
[UIView setAnimationDuration:0.7f];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationRepeatAutoreverses:NO];
[UIView setAnimationTransition:UIViewAnimationTransitionCurlDown forView:self.view cache:YES];
[currentView removeFromSuperview];
[self.view addSubview:contentView];
[UIView commitAnimations];
向上（向前）翻页，只需改为：
[UIView beginAnimations:@"animationID" context:nil];
[UIView setAnimationDuration:0.7f];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationRepeatAutoreverses:NO];
[UIView setAnimationTransition:UIViewAnimationTransitionCurlUpforView:self.view cache:YES];
[currentView removeFromSuperview];
[self.view addSubview:contentView];
[UIView commitAnimations];
如果是电子书，还需要考虑一个问题，就是有多个页面（图形），比如50页。那么需要有一个数据结构来保存这些页面的图片路径：
objc数据结构，比如数组
sqlite数据库表
这样，写一套翻页代码和加载什么图形之间就可以解耦。
本文示例使用的是数组，类似这样：
pages=[[NSArray alloc] initWithObjects:@"1.jpg",@"2.jpg",@"3.jpg",@"4.jpg",@"5.jpg",@"6.jpg",
???????????????? nil];
图片保存在resources下。
为了能让上页下页翻页的时候找到关联的页面，采用了如下机制：
将图片封装为UIImageView显示
可以为UIImageView设置一个tag值，值为数组下标+1
这样，上级view有方法能根据tag查询到UIImageView，比如：UIView *currentView=[self.view viewWithTag:currentTag];
设置一个成员变量currentTag保存当前的tag值
比如这样，当应用加载的时候显示第一页：
??? currentTag=1;
???
??? NSString *path = [[NSBundle mainBundle] pathForResource:@"pageflip1" ofType:@"mp3"];
??? player=[[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:NULL];
???
??? //[[UIApplication sharedApplication] setStatusBarHidden:YES animated:NO];
??? [[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation: UIStatusBarAnimationSlide];
??? UIImageView *contentView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];?
??? [contentView setImage:[UIImage imageNamed:[pages objectAtIndex:(currentTag-1)]]];?
??? [contentView setUserInteractionEnabled:YES];
??? contentView.tag=currentTag;
在翻页时的处理：
if (currentTag<[pages count]) {
??? UIView *currentView=[self.view viewWithTag:currentTag];
??? currentTag++;
???
??? UIImageView *contentView = [[UIImageView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
??? [contentView setImage:[UIImage imageNamed:[pages objectAtIndex:(currentTag-1)]]];?
??? [contentView setUserInteractionEnabled:YES];
??? contentView.tag=currentTag;
???
??? [UIView beginAnimations:@"animationID" context:nil];
??? [UIView setAnimationDuration:0.7f];
??? [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
??? [UIView setAnimationRepeatAutoreverses:NO];
??? [UIView setAnimationTransition:UIViewAnimationTransitionCurlUp forView:self.view cache:YES];
???
??? [currentView removeFromSuperview];
??? [self.view addSubview:contentView];
???
??? [UIView commitAnimations];
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