iOS使用UIGestureRecognizer识别手势

UIKit中包含了UIGestureRecognizer类，用于检测发生在设备中的手势。UIGestureRecognizer是一个抽象类，定义了所有手势的 基本行为，它有下面一些子类用于处理具体的手势：
1、拍击UITapGestureRecognizer (任意次数的拍击)
2、向里或向外捏UIPinchGestureRecognizer (用于缩放)
3、摇动或者拖拽UIPanGestureRecognizer
4、擦碰UISwipeGestureRecognizer (以任意方向)
5、旋转UIRotationGestureRecognizer (手指朝相反方向移动)
6、长按UILongPressGestureRecognizer对于不同类型的手势识别器，具有不同的配置属性。比如UITapGest ureRecognizer，可以配置拍击次数。界面接收到手势之后，可以发送一个消息，用于处理响应手势动作后的任务。当然，不同的手势识别器，发送的消息方法也会 有所不同。

// 创建一个手势识别器
UITapGestureRecognizer *oneFingerTwoTaps =
  [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(oneFingerTwoTaps)] autorelease];

// Set required taps and number of touches
[oneFingerTwoTaps setNumberOfTapsRequired:2];
[oneFingerTwoTaps setNumberOfTouchesRequired:1];

// Add the gesture to the view
[[self view] addGestureRecognizer:oneFingerTwoTaps];

消息方法oneFingerTwoTaps
- (void)oneFingerTwoTaps
{
  NSLog(@"Action: One finger,two taps");
}

UITapGestureRecognizer *twoFingersTwoTaps =
  [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(twoFingersTwoTaps)] autorelease];
[twoFingersTwoTaps setNumberOfTapsRequired:2];
[twoFingersTwoTaps setNumberOfTouchesRequired:2];
[[self view] addGestureRecognizer:twoFingersTwoTaps];

消息方法twoFingersTwoTaps
- (void)twoFingersTwoTaps {
  NSLog(@"Action: Two fingers,two taps");
} 

// 向上擦碰
UISwipeGestureRecognizer *oneFingerSwipeUp =
  [[[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(oneFingerSwipeUp:)] autorelease];
[oneFingerSwipeUp setDirection:UISwipeGestureRecognizerDirectionUp];
[[self view] addGestureRecognizer:oneFingerSwipeUp];

- (void)oneFingerSwipeUp:(UISwipeGestureRecognizer *)recognizer
{
  CGPoint point = [recognizer locationInView:[self view]];
  NSLog(@"Swipe up - start location: %f,%f",point.x,point.y);
}

// 向下擦碰
UISwipeGestureRecognizer *oneFingerSwipeDown =
  [[[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(oneFingerSwipeDown:)] autorelease];
[oneFingerSwipeDown setDirection:UISwipeGestureRecognizerDirectionDown];
[[self view] addGestureRecognizer:oneFingerSwipeDown];

- (void)oneFingerSwipeDown:(UISwipeGestureRecognizer *)recognizer
{
  CGPoint point = [recognizer locationInView:[self view]];
  NSLog(@"Swipe down - start location: %f,point.y);
}

UIRotationGestureRecognizer *twoFingersRotate =
  [[[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(twoFingersRotate:)] autorelease];
[[self view] addGestureRecognizer:twoFingersRotate];

- (void)twoFingersRotate:(UIRotationGestureRecognizer *)recognizer
{
  // Convert the radian value to show the degree of rotation
  NSLog(@"Rotation in degrees since last change: %f",[recognizer rotation] * (180 / M_PI));
}

UIPinchGestureRecognizer *twoFingerPinch =
  [[[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(twoFingerPinch:)] autorelease];
[[self view] addGestureRecognizer:twoFingerPinch];

- (void)twoFingerPinch:(UIPinchGestureRecognizer *)recognizer
{
  NSLog(@"Pinch scale: %f",recognizer.scale);
}