1、UIGestureRecognizer介绍
手势识别在iOS上非常重要，手势操作移动设备的重要特征，极大的增加了移动设备使用便捷性。
iOS系统在3.2以后，为方便开发这使用一些常用的手势，提供了UIGestureRecognizer类。手势识别UIGestureRecognizer类是个抽象类，下面的子类是具体的手势，开发这可以直接使用这些手势识别。
- Tap（点一下）
- Pinch（二指往內或往外拨动，平时经常用到的缩放）
- Rotation（旋转）
- Swipe（滑动，快速移动）
- Pan （拖移，慢速移动）
- LongPress（长按）
UIGestureRecognizer的继承关系如下：
2、使用手势的步骤
使用手势很简单，分为两步：
- 创建手势实例。当创建手势时，指定一个回调方法，当手势开始，改变、或结束时，回调方法被调用。
- 添加到需要识别的View中。每个手势只对应一个View，当屏幕触摸在View的边界内时，如果手势和预定的一样，那就会回调方法。
ps：一个手势只能对应一个View，但是一个View可以有多个手势。
建议在真机上运行这些手势,模拟器操作不太方便，可能导致你认为手势失效。
3、Pan 拖动手势：
UIImageView *snakeImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snake.png"]]; snakeImageView.frame = CGRectMake(50, 50, 100, 160); UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)]; [snakeImageView addGestureRecognizer:panGestureRecognizer]; [self.view setBackgroundColor:[UIColor whiteColor]]; [self.view addSubview:snakeImageView];新建一个ImageView，然后添加手势
回调方法：
- (void) handlePan:(UIPanGestureRecognizer*) recognizer{ CGPoint translation = [recognizer translationInView:self.view]; recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y); [recognizer setTranslation:CGPointZero inView:self.view]; } 4、Pinch缩放手势
UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];
[snakeImageView addGestureRecognizer:pinchGestureRecognizer];
- (void) handlePinch:(UIPinchGestureRecognizer*) recognizer{ recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale); recognizer.scale = 1;} 5、Rotation旋转手势
UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(handleRotate:)]; [snakeImageView addGestureRecognizer:rotateRecognizer];
- (void) handleRotate:(UIRotationGestureRecognizer*) recognizer{ recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation); recognizer.rotation = 0;} 
添加了这几个手势后，运行看效果，程序中的imageView放了一个
/^\/^\
_|__| O|
\/ /~ \_/ \
\____|__________/ \
\_______ \
`\ \ \
| | \
/ / \
/ / \\
/ / \ \
/ / \ \
/ / _----_ \ \
/ / _-~ ~-_ | |
( ( _-~ _--_ ~-_ _/ |
\ ~-____-~ _-~ ~-_ ~-_-~ /
~-_ _-~ ~-_ _-~
~--______-~ ~-___-~
的图片，在模拟器上拖动是没问题的。缩放和旋转有点问题，估计是因为在模拟器上的模拟的两个接触点距离在imageView的边界外了，所以操作无效果。
建议在真机上运行这个手势。
在模拟器上缩放和选择的操作技巧：
可以把imageView的frame值设置大一点，按住alt键，按下触摸板(不按下不行)，这样就可以旋转和缩放了。
6、添加第二个ImagView并添加手势
记住：一个手势只能添加到一个View，两个View当然要有两个手势的实例了
- (void)viewDidLoad{ [super viewDidLoad]; UIImageView *snakeImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"snake.png"]]; UIImageView *dragonImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"dragon.png"]]; snakeImageView.frame = CGRectMake(120, 120, 100, 160); dragonImageView.frame = CGRectMake(50, 50, 100, 160); [self.view addSubview:snakeImageView]; [self.view addSubview:dragonImageView]; for (UIView *view in self.view.subviews) { UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)]; UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)]; UIRotationGestureRecognizer *rotateRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(handleRotate:)]; [view addGestureRecognizer:panGestureRecognizer]; [view addGestureRecognizer:pinchGestureRecognizer]; [view addGestureRecognizer:rotateRecognizer]; [view setUserInteractionEnabled:YES]; } [self.view setBackgroundColor:[UIColor whiteColor]]; } 多添加了一条龙的view，两个view都能接收上面的三种手势。运行效果如下： 
7、拖动(pan手势)速度(以较快的速度拖放后view有滑行的效果)
如何实现呢？
- 监视手势是否结束
- 监视触摸的速度
- (void) handlePan:(UIPanGestureRecognizer*) recognizer{ CGPoint translation = [recognizer translationInView:self.view]; recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y); [recognizer setTranslation:CGPointZero inView:self.view]; if (recognizer.state == UIGestureRecognizerStateEnded) { CGPoint velocity = [recognizer velocityInView:self.view]; CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y)); CGFloat slideMult = magnitude / 200; NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult); float slideFactor = 0.1 * slideMult; // Increase for more of a slide CGPoint finalPoint = CGPointMake(recognizer.view.center.x + (velocity.x * slideFactor), recognizer.view.center.y + (velocity.y * slideFactor)); finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width); finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height); [UIView animateWithDuration:slideFactor*2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{ recognizer.view.center = finalPoint; } completion:nil]; }代码实现解析： - 计算速度向量的长度（估计大部分都忘了）这些知识了。
- 如果速度向量小于200，那就会得到一个小于的小数，那么滑行会很短
- 基于速度和速度因素计算一个终点
- 确保终点不会跑出父View的边界
- 使用UIView动画使view滑动到终点
运行后，快速拖动图像view 放开会看到view还会在原来的方向滑行一段路。
8、同时触发两个view的手势
手势之间是互斥的，如果你想同时触发蛇和龙的view，那么需要实现协议
UIGestureRecognizerDelegate，
@interface ViewController : UIViewController并在协议这个方法里返回YES。@end
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer{ return YES;}把self作为代理设置给手势： panGestureRecognizer.delegate = self; pinchGestureRecognizer.delegate = self; rotateRecognizer.delegate = self;这样可以同时拖动或旋转缩放两个view了。
9、tap点击手势
这里为了方便看到tap的效果，当点击一下屏幕时，播放一个声音。
为了播放声音，我们加入AVFoundation.framework这个框架。
- (AVAudioPlayer *)loadWav:(NSString *)filename { NSURL * url = [[NSBundle mainBundle] URLForResource:filename withExtension:@"wav"]; NSError * error; AVAudioPlayer * player = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error]; if (!player) { NSLog(@"Error loading %@: %@", url, error.localizedDescription); } else { [player prepareToPlay]; } return player;}我会在最后例子代码给出完整代码，添加手势的步骤和前面一样的。 #import#import @interface ViewController : UIViewController @property (strong) AVAudioPlayer * chompPlayer;@property (strong) AVAudioPlayer * hehePlayer;@end
- (void)handleTap:(UITapGestureRecognizer *)recognizer { [self.chompPlayer play];} 运行，点一下某个图，就会播放一个咬东西的声音。
不过这个点击播放声音有点缺陷，就是在慢慢拖动的时候也会播放。这使得两个手势重合了。怎么解决呢？使用手势的：requireGestureRecognizerToFail方法。
10、手势的依赖性
在viewDidLoad的循环里添加这段代码：
[tapRecognizer requireGestureRecognizerToFail:panGestureRecognizer];意思就是，当如果pan手势失败，就是没发生拖动，才会出发tap手势。这样如果你有轻微的拖动，那就是pan手势发生了。tap的声音就不会发出来了。
11、自定义手势
自定义手势继承：UIGestureRecognizer，实现下面的方法：
– touchesBegan:withEvent:– touchesMoved:withEvent:– touchesEnded:withEvent:- touchesCancelled:withEvent:
新建一个类，继承UIGestureRecognizer，代码如下：
.h文件
#import.m文件typedef enum { DirectionUnknown = 0, DirectionLeft, DirectionRight} Direction;@interface HappyGestureRecognizer : UIGestureRecognizer@property (assign) int tickleCount;@property (assign) CGPoint curTickleStart;@property (assign) Direction lastDirection;@end
#import "HappyGestureRecognizer.h"#import调用自定义手势和上面一样，回到这样写：#define REQUIRED_TICKLES 2#define MOVE_AMT_PER_TICKLE 25@implementation HappyGestureRecognizer- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch * touch = [touches anyObject]; self.curTickleStart = [touch locationInView:self.view];}- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { // Make sure we've moved a minimum amount since curTickleStart UITouch * touch = [touches anyObject]; CGPoint ticklePoint = [touch locationInView:self.view]; CGFloat moveAmt = ticklePoint.x - self.curTickleStart.x; Direction curDirection; if (moveAmt < 0) { curDirection = DirectionLeft; } else { curDirection = DirectionRight; } if (ABS(moveAmt) < MOVE_AMT_PER_TICKLE) return; // 确认方向改变了 if (self.lastDirection == DirectionUnknown || (self.lastDirection == DirectionLeft && curDirection == DirectionRight) || (self.lastDirection == DirectionRight && curDirection == DirectionLeft)) { // 挠痒次数 self.tickleCount++; self.curTickleStart = ticklePoint; self.lastDirection = curDirection; // 一旦挠痒次数超过指定数，设置手势为结束状态 // 这样回调函数会被调用。 if (self.state == UIGestureRecognizerStatePossible && self.tickleCount > REQUIRED_TICKLES) { [self setState:UIGestureRecognizerStateEnded]; } } }- (void)reset { self.tickleCount = 0; self.curTickleStart = CGPointZero; self.lastDirection = DirectionUnknown; if (self.state == UIGestureRecognizerStatePossible) { [self setState:UIGestureRecognizerStateFailed]; }}- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{ [self reset];}- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event{ [self reset];}@end
- (void)handleHappy:(HappyGestureRecognizer *)recognizer{ [self.hehePlayer play];}手势成功后播放呵呵笑的声音。 在真机上运行，按住某个view，快速左右拖动，就会发出笑的声音了。 代码解析：
先获取起始坐标： curTickleStart
通过和 ticklePoint的x值对比，得出当前的放下是向左还是向右。再算出移动的x的值是否比 MOVE_AMT_PER_TICKLE距离大，如果太则返回。
再判断是否有三次是不同方向的动作，如果是则手势结束，回调。
参考：http://www.raywenderlich.com/6567/uigesturerecognizer-tutorial-in-ios-5-pinches-pans-and-more
例子代码：
容芳志 ()
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