tap是指轻触手势。类似鼠标操作的点击。从iOS 3.2版本开始支持完善的手势api：
- tap：轻触
- long press：在一点上长按
- pinch：两个指头捏或者放的操作
- pan：手指的拖动
- swipe：手指在屏幕上很快的滑动
- rotation：手指反向操作
这为开发者编写手势识别操作，提供了很大的方便，想想之前用android写手势滑动的代码（ 编写android简单的手势切换视图示例 ），尤其感到幸福。
这里写一个简单的tap操作。在下面视图的蓝色视图内增加对tap的识别：
当用手指tap蓝色视图的时候，打印日志输出：
代码很简单，首先要声明tap的recognizer：
UITapGestureRecognizer *recognizer=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapFrom:)];
[infoView addGestureRecognizer:recognizer];
[recognizer release];
在这里：
- initWithTarget:self，要引用到Controller，因为一般这部分代码写在controller中，用self；
- action:@selector(handleTapFrom:)，赋值一个方法名，用于当手势事件发生后的回调；
- [infoView addGestureRecognizer:recognizer]，为view注册这个手势识别对象，这样当手指在该视图区域内，可引发手势，之外则不会引发
对应的回调方法：
-(void)handleTapFrom:(UITapGestureRecognizer *)recognizer{
NSLog(@">>>tap it");
}
controller相关方法完整的代码（包含了一些与本文无关的视图构建代码）：
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
//去掉最顶端的状态拦
[[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation: UIStatusBarAnimationSlide];
UIImage *image=[UIImage imageNamed:@"3.jpg"];
//创建背景视图
self.view=[[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
UIImageView *backgroudView=[[UIImageView alloc] initWithImage:image];
[self.view addSubview:backgroudView];
/*
UIToolbar *toolBar=[[UIToolbar alloc] initWithFrame:CGRectMake(0, 1024-70, 768, 70)];
toolBar.alpha=0.8;
toolBar.tintColor = [UIColor colorWithRed:.3 green:.5 blue:.6 alpha:.1];
NSArray *items=[NSArray arrayWithObjects:[[UIBarButtonItem alloc] initWithTitle:@"test" style:UIBarButtonItemStyleDone target:self action:nil],nil];
toolBar.items=items;
[self.view addSubview:toolBar];
*/
UIView *bottomView=[[UIView alloc] initWithFrame:CGRectMake(0, 1024-70, 768, 70)];
bottomView.backgroundColor=[UIColor grayColor];
bottomView.alpha=0.8;
//UIButton *backButton=[[UIButton alloc] initWithFrame:CGRectMake(10, 10, 100, 40)];
UIButton *backButton=[UIButton buttonWithType: UIButtonTypeRoundedRect];
[backButton setTitle:@"ok" forState:UIControlStateNormal];
backButton.frame=CGRectMake(10, 15, 100, 40);
[bottomView addSubview:backButton];
[self.view addSubview:bottomView];
UIView *infoView=[[UIView alloc] initWithFrame:CGRectMake(200, 700, 768-400, 70)];
infoView.backgroundColor=[UIColor blueColor];
infoView.alpha=0.6;
infoView.layer.cornerRadius=6;
infoView.layer.masksToBounds=YES;
[self.view addSubview:infoView];
UITapGestureRecognizer *recognizer=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapFrom:)];
[infoView addGestureRecognizer:recognizer];
[recognizer release];
}-(void)handleTapFrom:(UITapGestureRecognizer *)recognizer{
NSLog(@">>>tap it");
}
翻页效果，类似下面的样子：
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: UIViewAnimationTransitionCurlUp forView: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];
