1、UIGestureRecognizer 介绍

手势识别在 iOS 中非常重要，他极大地提高了移动设备的使用便捷性。

iOS 系统在 3.2 以后，他提供了一些常用的手势（UIGestureRecognizer 的子类），开发者可以直接使用他们进行手势操作。

UIPanGestureRecognizer（拖动）

UIPinchGestureRecognizer（捏合）

UIRotationGestureRecognizer（旋转）

UITapGestureRecognizer（点按）

UILongPressGestureRecognizer（长按）

​UISwipeGestureRecognizer（轻扫）

另外，可以通过继承 UIGestureRecognizer 类，实现自定义手势（手势识别器类）。

PS：自定义手势时，需要 #import <UIKit/UIGestureRecognizerSubclass.h>，一般需实现如下方法：

- (void)reset;

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;
//以上方法在分类 UIGestureRecognizer (UIGestureRecognizerProtected) 中声明，更多方法声明请自行查看

UIGestureRecognizer 的继承关系如下：

2、手势状态
在六种手势识别中，只有一种手势是离散型手势，他就是 UITapGestureRecognizer。
离散型手势的特点就是：一旦识别就无法取消，而且只会调用一次手势操作事件（初始化手势时指定的回调方法）。
​换句话说其他五种手势是连续型手势，而连续型手势的特点就是：会多次调用手势操作事件，而且在连续手势识别后可以取消手势。从下图可以看出两者调用操作事件的次数是不同的：

typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
    UIGestureRecognizerStatePossible,   // 尚未识别是何种手势操作（但可能已经触发了触摸事件），默认状态
    UIGestureRecognizerStateBegan,      // 手势已经开始，此时已经被识别，但是这个过程中可能发生变化，手势操作尚未完成
    UIGestureRecognizerStateChanged,    // 手势状态发生转变
    UIGestureRecognizerStateEnded,      // 手势识别操作完成（此时已经松开手指）
    UIGestureRecognizerStateCancelled,  // 手势被取消，恢复到默认状态
    UIGestureRecognizerStateFailed,     // 手势识别失败，恢复到默认状态
    UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded // 手势识别完成，同UIGestureRecognizerStateEnded
};

对于离散型手势 UITapGestureRecgnizer 要么被识别，要么失败，点按（假设点按次数设置为1，并且没有添加长按手势）下去一次不松开则此时什么也不会发生，松开手指立即识别并调用操作事件，并且状态为3（已完成）。
但是连续型手势要复杂一些，就拿旋转手势来说，如果两个手指点下去不做任何操作，此时并不能识别手势（因为我们还没旋转）但是其实已经触发了触摸开始事件，此时处于状态0；如果此时旋转会被识别，也就会调用对应的操作事件，同时状态变成1（手势开始），但是状态1只有一瞬间；紧接着状态变为2（因为我们的旋转需要持续一会），并且重复调用操作事件（如果在事件中打印状态会重复打印2）；松开手指，此时状态变为3，并调用1次操作事件。

3、使用手势的步骤
使用手势很简单，分为三步：
创建手势识别器对象实例。创建时，指定一个回调方法，当手势开始，改变、或结束时，执行回调方法。

设置手势识别器对象实例的相关属性（可选部分）

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，那就会执行回调方法。

PS：一个手势只能对应一个 View，但是一个 View 可以有多个手势。建议在真机上测试这些手势，模拟器操作不太方便，可能导致认为手势失效的情况。（模拟器测试捏合和旋转手势时，按住 option 键，再用触摸板或鼠标操作）

4、举例说明
功能描述：
附加到两个图片视图 UIImageView 的有『拖动』、『捏合』、『旋转』、『点按』；
而『轻扫』和『自定义手势 KMGestureRecognizer』附加在根视图 UIView 中。
拖动：进行当前图片视图位置移动

捏合：进行当前图片视图缩放

旋转：进行当前图片视图角度旋转

点按：双击恢复当前图片视图的缩放、角度旋转、不透明度

长按：设置当前图片视图的不透明度为0.7

轻扫：左右轻扫设置两个图片视图为居中，同时以垂直居中的特定偏移量定位

自定义手势：挠痒功能，左右扫动共3次或以上，设置两个图片视图为居中，同时以水平居中的特定偏移量定位

效果如下：

#import <UIKit/UIKit.h>

typedef NS_ENUM(NSUInteger, Direction) {
    DirectionUnknown,
    DirectionLeft,
    DirectionRight
};

@interface KMGestureRecognizer : UIGestureRecognizer
@property (assign, nonatomic) NSUInteger tickleCount; //挠痒次数
@property (assign, nonatomic) CGPoint currentTickleStart; //当前挠痒开始坐标位置
@property (assign, nonatomic) Direction lastDirection; //最后一次挠痒方向

@end

KMGestureRecognizer.m

#import "KMGestureRecognizer.h"
#import <UIKit/UIGestureRecognizerSubclass.h>

@implementation KMGestureRecognizer
#define kMinTickleSpacing 20.0
#define kMaxTickleCount 3

- (void)reset {
    _tickleCount = 0;
    _currentTickleStart = CGPointZero;
    _lastDirection = DirectionUnknown;
    
    if (self.state == UIGestureRecognizerStatePossible) {
        self.state = UIGestureRecognizerStateFailed;
    }
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    _currentTickleStart = [touch locationInView:self.view]; //设置当前挠痒开始坐标位置
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    //『当前挠痒开始坐标位置』和『移动后坐标位置』进行 X 轴值比较，得到是向左还是向右移动
    UITouch *touch = [touches anyObject];
    CGPoint tickleEnd = [touch locationInView:self.view];
    CGFloat tickleSpacing = tickleEnd.x - _currentTickleStart.x;
    Direction currentDirection = tickleSpacing < 0 ? DirectionLeft : DirectionRight;
    
    //移动的 X 轴间距值是否符合要求，足够大
    if (ABS(tickleSpacing) >= kMinTickleSpacing) {
        //判断是否有三次不同方向的动作，如果有则手势结束，将执行回调方法
        if (_lastDirection == DirectionUnknown ||
            (_lastDirection == DirectionLeft && currentDirection == DirectionRight) ||
            (_lastDirection == DirectionRight && currentDirection == DirectionLeft)) {
            _tickleCount++;
            _currentTickleStart = tickleEnd;
            _lastDirection = currentDirection;
            
            if (_tickleCount >= kMaxTickleCount && self.state == UIGestureRecognizerStatePossible) {
                self.state = UIGestureRecognizerStateEnded;
                //NSLog(@"自定义手势成功，将执行回调方法");
            }
        }
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [self reset];
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    [self reset];
}

@end

ViewController.h

#import <UIKit/UIKit.h>
#import "KMGestureRecognizer.h"

@interface ViewController : UIViewController
@property (strong, nonatomic) UIImageView *imgV;
@property (strong, nonatomic) UIImageView *imgV2;
@property (strong, nonatomic) KMGestureRecognizer *customGestureRecognizer;

@end

ViewController.m

#import "ViewController.h"

@interface ViewController ()
- (void)handlePan:(UIPanGestureRecognizer *)recognizer;
- (void)handlePinch:(UIPinchGestureRecognizer *)recognizer;
- (void)handleRotation:(UIRotationGestureRecognizer *)recognizer;
- (void)handleTap:(UITapGestureRecognizer *)recognizer;
- (void)handleLongPress:(UILongPressGestureRecognizer *)recognizer;
- (void)handleSwipe:(UISwipeGestureRecognizer *)recognizer;
- (void)handleCustomGestureRecognizer:(KMGestureRecognizer *)recognizer;

- (void)bindPan:(UIImageView *)imgVCustom;
- (void)bindPinch:(UIImageView *)imgVCustom;
- (void)bindRotation:(UIImageView *)imgVCustom;
- (void)bindTap:(UIImageView *)imgVCustom;
- (void)bindLongPress:(UIImageView *)imgVCustom;
- (void)bindSwipe;
- (void)bingCustomGestureRecognizer;
- (void)layoutUI;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self layoutUI];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - 处理手势操作
/**
 *  处理拖动手势
 *
 *  @param recognizer 拖动手势识别器对象实例
 */
- (void)handlePan:(UIPanGestureRecognizer *)recognizer {
    //视图前置操作
    [recognizer.view.superview bringSubviewToFront:recognizer.view];
    
    CGPoint center = recognizer.view.center;
    CGFloat cornerRadius = recognizer.view.frame.size.width / 2;
    CGPoint translation = [recognizer translationInView:self.view];
    //NSLog(@"%@", NSStringFromCGPoint(translation));
    recognizer.view.center = CGPointMake(center.x + translation.x, center.y + translation.y);
    [recognizer setTranslation:CGPointZero inView:self.view];
    
    if (recognizer.state == UIGestureRecognizerStateEnded) {
        //计算速度向量的长度，当他小于200时，滑行会很短
        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); //e.g. 397.973175, slideMult: 1.989866
        
        //基于速度和速度因素计算一个终点
        float slideFactor = 0.1 * slideMult;
        CGPoint finalPoint = CGPointMake(center.x + (velocity.x * slideFactor),
                                         center.y + (velocity.y * slideFactor));
        //限制最小［cornerRadius］和最大边界值［self.view.bounds.size.width - cornerRadius］，以免拖动出屏幕界限
        finalPoint.x = MIN(MAX(finalPoint.x, cornerRadius),
                           self.view.bounds.size.width - cornerRadius);
        finalPoint.y = MIN(MAX(finalPoint.y, cornerRadius),
                           self.view.bounds.size.height - cornerRadius);
        
        //使用 UIView 动画使 view 滑行到终点
        [UIView animateWithDuration:slideFactor*2
                              delay:0
                            options:UIViewAnimationOptionCurveEaseOut
                         animations:^{
                             recognizer.view.center = finalPoint;
                         }
                         completion:nil];
    }
}

/**
 *  处理捏合手势
 *
 *  @param recognizer 捏合手势识别器对象实例
 */
- (void)handlePinch:(UIPinchGestureRecognizer *)recognizer {
    CGFloat scale = recognizer.scale;
    recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, scale, scale); //在已缩放大小基础下进行累加变化；区别于：使用 CGAffineTransformMakeScale 方法就是在原大小基础下进行变化
    recognizer.scale = 1.0;
}

/**
 *  处理旋转手势
 *
 *  @param recognizer 旋转手势识别器对象实例
 */
- (void)handleRotation:(UIRotationGestureRecognizer *)recognizer {
    recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
    recognizer.rotation = 0.0;
}

/**
 *  处理点按手势
 *
 *  @param recognizer 点按手势识别器对象实例
 */
- (void)handleTap:(UITapGestureRecognizer *)recognizer {
    UIView *view = recognizer.view;
    view.transform = CGAffineTransformMakeScale(1.0, 1.0);
    view.transform = CGAffineTransformMakeRotation(0.0);
    view.alpha = 1.0;
}

/**
 *  处理长按手势
 *
 *  @param recognizer 点按手势识别器对象实例
 */
- (void)handleLongPress:(UILongPressGestureRecognizer *)recognizer {
    //长按的时候，设置不透明度为0.7
    recognizer.view.alpha = 0.7;
}

/**
 *  处理轻扫手势
 *
 *  @param recognizer 轻扫手势识别器对象实例
 */
- (void)handleSwipe:(UISwipeGestureRecognizer *)recognizer {
    //代码块方式封装操作方法
    void (^positionOperation)() = ^() {
        CGPoint newPoint = recognizer.view.center;
        newPoint.y -= 20.0;
        _imgV.center = newPoint;
        
        newPoint.y += 40.0;
        _imgV2.center = newPoint;
    };
    
    //根据轻扫方向，进行不同控制
    switch (recognizer.direction) {
        case UISwipeGestureRecognizerDirectionRight: {
            positionOperation();
            break;
        }
        case UISwipeGestureRecognizerDirectionLeft: {
            positionOperation();
            break;
        }
        case UISwipeGestureRecognizerDirectionUp: {
            break;
        }
        case UISwipeGestureRecognizerDirectionDown: {
            break;
        }
    }
}

/**
 *  处理自定义手势
 *
 *  @param recognizer 自定义手势识别器对象实例
 */
- (void)handleCustomGestureRecognizer:(KMGestureRecognizer *)recognizer {
    //代码块方式封装操作方法
    void (^positionOperation)() = ^() {
        CGPoint newPoint = recognizer.view.center;
        newPoint.x -= 20.0;
        _imgV.center = newPoint;
        
        newPoint.x += 40.0;
        _imgV2.center = newPoint;
    };
    
    positionOperation();
}


#pragma mark - 绑定手势操作
/**
 *  绑定拖动手势
 *
 *  @param imgVCustom 绑定到图片视图对象实例
 */
- (void)bindPan:(UIImageView *)imgVCustom {
    UIPanGestureRecognizer *recognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self
                                                                                 action:@selector(handlePan:)];
    [imgVCustom addGestureRecognizer:recognizer];
}

/**
 *  绑定捏合手势
 *
 *  @param imgVCustom 绑定到图片视图对象实例
 */
- (void)bindPinch:(UIImageView *)imgVCustom {
    UIPinchGestureRecognizer *recognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self
                                                                                     action:@selector(handlePinch:)];
    [imgVCustom addGestureRecognizer:recognizer];
    //[recognizer requireGestureRecognizerToFail:imgVCustom.gestureRecognizers.firstObject];
}

/**
 *  绑定旋转手势
 *
 *  @param imgVCustom 绑定到图片视图对象实例
 */
- (void)bindRotation:(UIImageView *)imgVCustom {
    UIRotationGestureRecognizer *recognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self
                                                                                           action:@selector(handleRotation:)];
    [imgVCustom addGestureRecognizer:recognizer];
}

/**
 *  绑定点按手势
 *
 *  @param imgVCustom 绑定到图片视图对象实例
 */
- (void)bindTap:(UIImageView *)imgVCustom {
    UITapGestureRecognizer *recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self
                                                                                 action:@selector(handleTap:)];
    //使用一根手指双击时，才触发点按手势识别器
    recognizer.numberOfTapsRequired = 2;
    recognizer.numberOfTouchesRequired = 1;
    [imgVCustom addGestureRecognizer:recognizer];
}

/**
 *  绑定长按手势
 *
 *  @param imgVCustom 绑定到图片视图对象实例
 */
- (void)bindLongPress:(UIImageView *)imgVCustom {
    UILongPressGestureRecognizer *recognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPress:)];
    recognizer.minimumPressDuration = 0.5; //设置最小长按时间；默认为0.5秒
    [imgVCustom addGestureRecognizer:recognizer];
}

/**
 *  绑定轻扫手势；支持四个方向的轻扫，但是不同的方向要分别定义轻扫手势
 */
- (void)bindSwipe {
    //向右轻扫手势
    UISwipeGestureRecognizer *recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self
                                                                                     action:@selector(handleSwipe:)];
    recognizer.direction = UISwipeGestureRecognizerDirectionRight; //设置轻扫方向；默认是 UISwipeGestureRecognizerDirectionRight，即向右轻扫
    [self.view addGestureRecognizer:recognizer];
    [recognizer requireGestureRecognizerToFail:_customGestureRecognizer]; //设置以自定义挠痒手势优先识别
    
    //向左轻扫手势
    recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self
                                                           action:@selector(handleSwipe:)];
    recognizer.direction = UISwipeGestureRecognizerDirectionLeft;
    [self.view addGestureRecognizer:recognizer];
    [recognizer requireGestureRecognizerToFail:_customGestureRecognizer]; //设置以自定义挠痒手势优先识别
}

/**
 *  绑定自定义挠痒手势；判断是否有三次不同方向的动作，如果有则手势结束，将执行回调方法
 */
- (void)bingCustomGestureRecognizer {
    //当 recognizer.state 为 UIGestureRecognizerStateEnded 时，才执行回调方法 handleCustomGestureRecognizer:
    
    //_customGestureRecognizer = [KMGestureRecognizer new];
    _customGestureRecognizer = [[KMGestureRecognizer alloc] initWithTarget:self
                                                                    action:@selector(handleCustomGestureRecognizer:)];
    [self.view addGestureRecognizer:_customGestureRecognizer];
}

- (void)layoutUI {
    //图片视图 _imgV
    UIImage *img = [UIImage imageNamed:@"Emoticon_tusiji_icon"];
    CGFloat cornerRadius = img.size.width;
    _imgV = [[UIImageView alloc] initWithImage:img];
    _imgV.frame = CGRectMake(20.0, 20.0,
                             cornerRadius * 2, cornerRadius * 2);
    _imgV.userInteractionEnabled = YES;
    _imgV.layer.masksToBounds = YES;
    _imgV.layer.cornerRadius = cornerRadius;
    _imgV.layer.borderWidth = 2.0;
    _imgV.layer.borderColor = [UIColor grayColor].CGColor;
    [self.view addSubview:_imgV];
    
    //图片视图 _imgV2
    img = [UIImage imageNamed:@"Emoticon_tusiji_icon2"];
    cornerRadius = img.size.width;
    _imgV2 = [[UIImageView alloc] initWithImage:img];
    _imgV2.frame = CGRectMake(20.0, 40.0 + _imgV.frame.size.height,
                              cornerRadius * 2, cornerRadius * 2);
    _imgV2.userInteractionEnabled = YES;
    _imgV2.layer.masksToBounds = YES;
    _imgV2.layer.cornerRadius = cornerRadius;
    _imgV2.layer.borderWidth = 2.0;
    _imgV2.layer.borderColor = [UIColor orangeColor].CGColor;
    [self.view addSubview:_imgV2];
    
    
    [self bindPan:_imgV];
    [self bindPinch:_imgV];
    [self bindRotation:_imgV];
    [self bindTap:_imgV];
    [self bindLongPress:_imgV];
    
    [self bindPan:_imgV2];
    [self bindPinch:_imgV2];
    [self bindRotation:_imgV2];
    [self bindTap:_imgV2];
    [self bindLongPress:_imgV2];
    
    //为了处理手势识别优先级的问题，这里需先绑定自定义挠痒手势
    [self bingCustomGestureRecognizer];
    [self bindSwipe];
}

@end

转自 KenmuHuang 网址：http://www.cnblogs.com/huangjianwu/p/4675648.html