tap是指輕觸手勢。類似鼠標操作的點擊。從iOS 3.2版本開始支持完善的手勢api：

• tap：輕觸
• long press：在一點上長按
• pinch：兩個指頭捏或者放的操作
• pan：手指的拖動
• swipe：手指在屏幕上很快的滑動
• rotation：手指反向操作

這為開發者編寫手勢識別操作，提供了很大的方便，想想之前用android寫手勢滑動的代碼（ 編寫android簡單的手勢切換視圖示例 ），尤其感到幸福。

這里寫一個簡單的tap操作。在下面視圖的藍色視圖內增加對tap的識別：

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當用手指tap藍色視圖的時候，打印日志輸出：

代碼很簡單，首先要聲明tap的recognizer：

UITapGestureRecognizer *recognizer=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTapFrom:)];
[infoView addGestureRecognizer:recognizer];
[recognizer release];

在這里：

• initWithTarget:self，要引用到Controller，因為一般這部分代碼寫在controller中，用self；
• action:@selector(handleTapFrom:)，賦值一個方法名，用于當手勢事件發生后的回調；
• [infoView addGestureRecognizer:recognizer]，為view注冊這個手勢識別對象，這樣當手指在該視圖區域內，可引發手勢，之外則不會引發

對應的回調方法：

-(void)handleTapFrom:(UITapGestureRecognizer *)recognizer{
??? NSLog(@">>>tap it");
}

controller相關方法完整的代碼（包含了一些與本文無關的視圖構建代碼）：

// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
??? //去掉最頂端的狀態攔
??? [[UIApplication sharedApplication] setStatusBarHidden:YES withAnimation: UIStatusBarAnimationSlide];
???
??? UIImage *image=[UIImage imageNamed:@"3.jpg"];
???
??? //創建背景視圖
??? 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");
}

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翻頁效果，類似下面的樣子：

在電子書應用中會很常見。這里需要兩個要點：

• 翻頁動畫
• 手勢上下輕掃（swipe）的處理

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先說一下輕掃（swipe）的實現，可以參考 編寫簡單的手勢示例：Tap 了解手勢種類。

在viewDidLoad方法中注冊了對上、下、左、右四個方向輕松的處理方法：

- (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];

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可以看到，都是同一個方法，handleSwipeFrom。

在該方法中，再識別具體是哪個方向的輕掃手勢，比如判斷是向下的輕掃：

-(void)handleSwipeFrom:(UISwipeGestureRecognizer *)recognizer {
??? NSLog(@"Swipe received.");
???
??? if (recognizer.direction==UISwipeGestureRecognizerDirectionDown) {
??????? NSLog(@"swipe down");

判斷是向上的輕掃：

if (recognizer.direction==UISwipeGestureRecognizerDirectionUp) {
??? NSLog(@"swipe up");

有關動畫的處理，比如向下（往回）翻頁，類似這樣：

[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）翻頁，只需改為：

[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];

如果是電子書，還需要考慮一個問題，就是有多個頁面（圖形），比如50頁。那么需要有一個數據結構來保存這些頁面的圖片路徑：

• objc數據結構，比如數組
• sqlite數據庫表

這樣，寫一套翻頁代碼和加載什么圖形之間就可以解耦。

本文示例使用的是數組，類似這樣：

pages=[[NSArray alloc] initWithObjects:@"1.jpg",@"2.jpg",@"3.jpg",@"4.jpg",@"5.jpg",@"6.jpg",
???????????????? nil];

圖片保存在resources下。

為了能讓上頁下頁翻頁的時候找到關聯的頁面，采用了如下機制：

• 將圖片封裝為UIImageView顯示
• 可以為UIImageView設置一個tag值，值為數組下標+1
• 這樣，上級view有方法能根據tag查詢到UIImageView，比如：UIView *currentView=[self.view viewWithTag:currentTag];
• 設置一個成員變量currentTag保存當前的tag值

比如這樣，當應用加載的時候顯示第一頁：

??? 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;

在翻頁時的處理：

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];

UISwipeGestureRecognizer ---手指動作