UISwipeGestureRecognizer 手指动作

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];